Articles de revues : « Carbone, Zenica »

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Durakovic, Mirnes, Azrudin Husika, Halim Prcanovic, Sanela Beganovic et Muvedet Sisic. « ANALYSIS OF THE RESULTS OF AIR QUALITY MONITORING IN THE AREA OF THE CITY OF ZENICA ». International Journal of Advanced Research 9, n^o 12 (31 décembre 2021) : 453–61. http://dx.doi.org/10.21474/ijar01/13930.

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According to the World Health Organization (WHO), air pollution is the largest single environmental risk to public health. According to the latest estimate of this organization, 9 out of 10 people on the planet breathe polluted air. The development of industry in the relatively small Zenica valley reflected on air quality in the city of Zenica. The problem of high air pollution due to emissions of pollutants from industrial sources, traffic, and individual furnaces, burning of environmentally unsuitable fuels containing high sulfur and ash content has been present in the City of Zenica for a long time. In addition, the low wind speed during the year, which ranges up to 1.5 m/s, with unfavorable temperature inversions, causes the concentrations of pollutants in the air to reach alarmingly high values in a short period. In the wider area of the City of Zenica, air quality has been monitored since 1978 in the network of stationary stations. The paper presents results of air quality monitoring which are analyzed at the Institute Kemal Kapetanovic in Zenica for the sampling period from 01.01.2019. to 31.12.2020. years. Air quality monitoring included sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and particulate matter (PM10) at three locations in the wider area of the city of Zenica. In the wider area of the City of Zenica, air quality has been monitored since 1978 in the network of stationary stations. The paper presents the processed results of air quality monitoring which are analyzed at the Institute Kemal Kapetanovic in Zenica for the sampling period from 01.01.2019 to 31.12.2020. The measured concentrations of pollutants in the ambient air indicate that during the heating season, i.e. the winter months, the air quality in the urban and suburban areas of the city of Zenica is very poor. The data show that the highest hourly concentration of sulfur dioxide was recorded in December at the measuring station AMS Tetovo in the amount of 1100.59 Ã‚Âµg/m3, which is located in the settlement next to the metallurgical facilities of the industrial zone Zenica.

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Lu, Mengzhen, Kunping Liu, Lijin Zhang, Fuping Zeng, Tongqing Song, Wanxia Peng et Hu Du. « Stoichiometric Variation in Soil Carbon, Nitrogen, and Phosphorus Following Cropland Conversion to Forest in Southwest China ». Forests 13, n^o 8 (22 juillet 2022) : 1155. http://dx.doi.org/10.3390/f13081155.

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Soil organic carbon (SOC), nitrogen (N), and phosphorus (P) are three essential soil nutrients for plant growth, and their stoichiometric ratios are already important indices of elemental balance and the soil fertility status in soil ecosystems. The evolution mechanism of the SOC, Total Nitrogen (TN), Total Phosphorus (TP), and stoichiometry following the “conversion of cropland to forest program” (CCFP) in southwest China is not yet clear. Seven different CCFP restoration models, including Zenia insignis (RD), Toona sinensis (XC), Castanea mollissima (BL), Citrus reticulate (GJ), Zenia insignis and Guimu-1 elephant grass (RG), Guimu-1 elephant grass (GM), and abandoned cropland (LH), were chosen to explore changes in the concentration and stoichiometry of the SOC, TN, and TP, and their recovery times, at a depth of 0–100 cm. The results indicate that the SOC and TN concentrations in different restoration models all increased with restoration years in the topsoil, whereas the soil TP concentration remained relatively stable. The soil C:N and C:P ratios increased with increasing restoration years in the topsoil, whereas the N: P ratio was relatively stable over time. After ten years of reforestation, the SOC and TN concentrations decreased as the soil layer increased. The effects of the restoration model on the C: N ratios were greater in shallow soils. Our results suggest a complex reaction of SOC, soil TN, and soil TP concentrations and stoichiometry to the vegetation restoration mode, particularly in the topsoil. This research further improves the understanding of SOC, N, and P interactions and restricted nutrition, and provides relevant theoretical support for vegetation restoration in the southwest karst region.

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Chan, H. G., M. D. King et M. M. Frey. « The impact of parameterising light penetration into snow on the photochemical production of NOx ; and OH radicals in snow ». Atmospheric Chemistry and Physics Discussions 15, n^o 6 (23 mars 2015) : 8609–46. http://dx.doi.org/10.5194/acpd-15-8609-2015.

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Abstract. Snow photochemical processes drive production of chemical trace gases, including nitrogen oxides (NO and NO2), and HOx radicals in snowpacks which are then released to the lower atmosphere. Coupled atmosphere–snow modelling on global scales requires simple parameterisations of actinic flux in snow to reduce computational cost. The disagreement between a physical radiative transfer method and a method based upon the e-folding depth of light-in snow is evaluated. In particular for the photolysis of the nitrate anion (NO3-), the nitrite anion (NO2-) and hydrogen peroxide (H2O2) within snow and photolysis of gas-phase nitrogen dioxide (NO2) within the snowpack interstitial air are considered. The emission flux from the snowpack is estimated as the depth-integrated photolysis rate, v, calculated (a) explicitly with a physical radiative transfer model (TUV), vTUV and (b) with a simple parameterisation based on e-folding depth, vze. The evaluation is based upon the deviation of the ratio of depth-integrated photolysis rate determined by the two methods,vTUV/vze, from unity. The disagreement in depth-integrated photolysis rate between the RT model and e-folding depth parameterisation depends primarily on the photolysis action spectrum of chemical species, solar zenith angle and optical properties of the snowpack, (scattering cross-section and a weak dependence on light absorbing impurity (black carbon) and density). For photolysis of NO2, the NO2- anion, the NO3- anion and H2O2 the ratio vTUV/vze varies within the range of 0.82–1.35, 0.88–1.28 and 0.92–1.27 respectively. The e-folding depth parameterisation underestimates for small solar zenith angles and overestimates at solar zenith angles around 60°. A simple algorithm has been developed to improve the parameterisation which reduced the ratio vTUV/vze to 0.97–1.02, 0.99–1.02 and 0.99–1.03 for photolysis of NO2, the NO2- anion, the NO3- anion and H2O2 respectively. The e-folding depth parameterisation may give acceptable results for the photolysis of the NO3- anion and H2O2 in cold polar snow with large solar zenith angles, but can be improved by a correction based on solar zenith angle.

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Zahn, Einara, Nelson L. Dias, Alessandro Araújo, Leonardo D. A. Sá, Matthias Sörgel, Ivonne Trebs, Stefan Wolff et Antônio Manzi. « Scalar turbulent behavior in the roughness sublayer of an Amazonian forest ». Atmospheric Chemistry and Physics 16, n^o 17 (13 septembre 2016) : 11349–66. http://dx.doi.org/10.5194/acp-16-11349-2016.

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Abstract. An important current problem in micrometeorology is the characterization of turbulence in the roughness sublayer (RSL), where most of the measurements above tall forests are made. There, scalar turbulent fluctuations display significant departures from the predictions of Monin–Obukhov similarity theory (MOST). In this work, we analyze turbulence data of virtual temperature, carbon dioxide, and water vapor in the RSL above an Amazonian forest (with a canopy height of 40 m), measured at 39.4 and 81.6 m above the ground under unstable conditions. We found that dimensionless statistics related to the rate of dissipation of turbulence kinetic energy (TKE) and the scalar variance display significant departures from MOST as expected, whereas the vertical velocity variance follows MOST much more closely. Much better agreement between the dimensionless statistics with the Obukhov similarity variable, however, was found for the subset of measurements made at a low zenith angle Z, in the range 0° < |Z| < 20°. We conjecture that this improvement is due to the relationship between sunlight incidence and the “activation–deactivation” of scalar sinks and sources vertically distributed in the forest. Finally, we evaluated the relaxation coefficient of relaxed eddy accumulation: it is also affected by zenith angle, with considerable improvement in the range 0° < |Z| < 20°, and its values fall within the range reported in the literature for the unstable surface layer. In general, our results indicate the possibility of better stability-derived flux estimates for low zenith angle ranges.

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Rohlffs, Fiona, Nikolaos Tsilimparis, Vasilis Saleptsis, Holger Diener, E. Sebastian Debus et Tilo Kölbel. « Air Embolism During TEVAR ». Journal of Endovascular Therapy 24, n^o 1 (26 octobre 2016) : 84–88. http://dx.doi.org/10.1177/1526602816675621.

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Purpose: To investigate the amount of gas released from Zenith thoracic stent-grafts using standard saline flushing vs the carbon dioxide flushing technique. Methods: In an experimental bench setting, 20 thoracic stent-grafts were separated into 2 groups of 10 endografts. One group of grafts was flushed with 60 mL saline and the other group was flushed with carbon dioxide for 5 minutes followed by 60 mL saline. All grafts were deployed into a water-filled container with a curved plastic pipe; the deployment was recorded and released gas was measured using a calibrated setup. Results: Gas was released from all grafts in both study groups during endograft deployment. The average amount of released gas per graft was significantly lower in the study group with carbon dioxide flushing (0.79 vs 0.51 mL, p=0.005). Conclusion: Thoracic endografts release significant amounts of air during deployment if flushed according to the instructions for use. Application of carbon dioxide for the flushing of thoracic stent-grafts prior to standard saline flush significantly reduces the amount of gas released during deployment. The additional use of carbon dioxide should be considered as a standard flush technique for aortic stent-grafts, especially in those implanted in proximal aortic segments, to reduce the risk of air embolism and stroke.

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Chan, H. G., M. D. King et M. M. Frey. « The impact of parameterising light penetration into snow on the photochemical production of NOx ; and OH radicals in snow ». Atmospheric Chemistry and Physics 15, n^o 14 (17 juillet 2015) : 7913–27. http://dx.doi.org/10.5194/acp-15-7913-2015.

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Abstract. Snow photochemical processes drive production of chemical trace gases in snowpacks, including nitrogen oxides (NOx = NO + NO2) and hydrogen oxide radical (HOx = OH + HO2), which are then released to the lower atmosphere. Coupled atmosphere–snow modelling of theses processes on global scales requires simple parameterisations of actinic flux in snow to reduce computational cost. The disagreement between a physical radiative-transfer (RT) method and a parameterisation based upon the e-folding depth of actinic flux in snow is evaluated. In particular, the photolysis of the nitrate anion (NO3-), the nitrite anion (NO2-) and hydrogen peroxide (H2O2) in snow and nitrogen dioxide (NO2) in the snowpack interstitial air are considered. The emission flux from the snowpack is estimated as the product of the depth-integrated photolysis rate coefficient, v, and the concentration of photolysis precursors in the snow. The depth-integrated photolysis rate coefficient is calculated (a) explicitly with an RT model (TUV), vTUV, and (b) with a simple parameterisation based on e-folding depth, vze. The metric for the evaluation is based upon the deviation of the ratio of the depth-integrated photolysis rate coefficient determined by the two methods, vTUV/vze, from unity. The ratio depends primarily on the position of the peak in the photolysis action spectrum of chemical species, solar zenith angle and physical properties of the snowpack, i.e. strong dependence on the light-scattering cross section and the mass ratio of light-absorbing impurity (i.e. black carbon and HULIS) with a weak dependence on density. For the photolysis of NO2, the NO2- anion, the NO3- anion and H2O2 the ratio vTUV/vze varies within the range of 0.82–1.35, 0.88–1.28, 0.93–1.27 and 0.91–1.28 respectively. The e-folding depth parameterisation underestimates for small solar zenith angles and overestimates at solar zenith angles around 60° compared to the RT method. A simple algorithm has been developed to improve the parameterisation which reduces the ratio vTUV/vze to 0.97–1.02, 0.99–1.02, 0.99–1.03 and 0.98–1.06 for photolysis of NO2, the NO2- anion, the NO3- anion and H2O2 respectively. The e-folding depth parameterisation may give acceptable results for the photolysis of the NO3- anion and H2O2 in cold polar snow with large solar zenith angles, but it can be improved by a correction based on solar zenith angle and for cloudy skies.

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Arulrajah, Kugarajah, Tilo Kölbel, Giuseppe Panuccio, Thomas Gandet et Fiona Rohlffs. « The Carbon Dioxide Flushing Technique : A Novel Approach Using Oxygen Measurements to Evaluate the Elimination of Room Air from Thoracic Stent-Grafts ». International Journal of Innovative Research in Medical Science 8, n^o 01 (2 janvier 2023) : 13–16. http://dx.doi.org/10.23958/ijirms/vol08-i01/1600.

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Background: The study evaluates a novel technique using oxygen measurements to indirectly evaluate the behavior of carbon dioxide (CO2) in the residual gas released by thoracic stent-grafts and to better understand the mechanism of the CO2 flushing technique. Methods: Ten Zenith TX2 ProForm thoracic stent-grafts (ZDEG-PT-34-199-PF, Cook Medical, Bjæverskov, Denmark) were equally divided into 2 groups (Group A and B). Group A was flushed with 60 ml of 0.9% saline. Group B was flushed with 100% carbon dioxide gas followed by 60 ml of 0.9% saline. The stent-grafts were deployed into a plastic tube that was placed and fixated to the bottom of a translucent container filled with water to collect the residual air released by the stent-grafts. Oxygen (O2) concentration and gas volume were measured in the released gas. Results: The oxygen concentration was significant (p<0.001) lower after additional carbon dioxide flush compared to standard flush (18.5% vs 19.6%). Furthermore, the absolute oxygen volume was significantly lower after additional carbon dioxide flush than without (0.18 ml vs 0.32 ml, p=0.041). The total amount of released gas appeared lower with carbon dioxide flush than without (0.98 ml vs 1.65, P=0.058). Conclusions: CO2 absorption into saline and replacement of room air by CO2 inside the stent-graft may lead to a reduction of released gas during stent-graft deployment in an experimental setting.

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Yu, Shanshan, Robert Rosenberg, Carol Bruegge, Lars Chapsky, Dejian Fu, Richard Lee, Thomas Taylor et al. « Stability Assessment of OCO-2 Radiometric Calibration Using Aqua MODIS as a Reference ». Remote Sensing 12, n^o 8 (17 avril 2020) : 1269. http://dx.doi.org/10.3390/rs12081269.

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With three imaging grating spectrometers, the Orbiting Carbon Observatory-2 (OCO-2) measures high spectral resolution spectra ( λ / Δ λ ≈ 19,000) of reflected solar radiation within the molecular oxygen (O 2 ) A-band at 0.765 μ m and two carbon dioxide (CO 2 ) bands at 1.61 and 2.06 μ m. OCO-2 uses onboard lamps with a reflective diffuser, solar observations through a transmissive diffuser, lunar measurements, and surface targets for radiometric calibration and validation. Separating calibrator aging from instrument degradation poses a challenge to OCO-2. Here we present a methodology for trending the OCO-2 Build 8R radiometric calibration using OCO-2 nadir observations over eight desert sites and nearly simultaneous observations from Moderate Resolution Imaging Spectroradiometer (MODIS) with sensor viewing zenith angles of 15 ± 0.5 ∘ . For the O 2 A-band, this methodology is able to quantify a drift of −0.8 ± 0.1% per year and capture a small error in correcting the aging of the solar calibrator. For the other two OCO-2 bands, no measurable changes were seen, indicating less than 0.1% and less than 0.3% per year drift in the radiometric calibration of Band 2 and Band 3, respectively.

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van Angelen, J. H., J. T. M. Lenaerts, S. Lhermitte, X. Fettweis, P. Kuipers Munneke, M. R. van den Broeke et E. van Meijgaard. « Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization : a study with a regional climate model ». Cryosphere Discussions 6, n^o 2 (24 avril 2012) : 1531–62. http://dx.doi.org/10.5194/tcd-6-1531-2012.

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Abstract. We present a sensitivity study of the surface mass balance (SMB) of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo parameterization. The snow albedo parameterization uses grain size as a prognostic variable and further depends on cloud cover, solar zenith angle and black carbon concentration. For the control experiment the overestimation of absorbed shortwave radiation (+6 %) at the K-transect (West Greenland) for the period 2004–2009 is considerably reduced compared to the previous density-dependent albedo parameterization (+22 %). To simulate realistic snow albedo values, a small concentration of black carbon is needed. A background ice albedo field derived from MODIS imagery improves the agreement between the modeled and observed SMB gradient along the K-transect. The effect of enhanced retention and refreezing is a decrease of the albedo due to an increase in snow grain size. As a secondary effect of refreezing the snowpack is heated, enhancing melt and further lowering the albedo. Especially in a warmer climate this process is important, since it reduces the refreezing potential of the firn layer covering the Greenland Ice Sheet.

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Wajid, Itab, et Ahmed Al-Rubaiee. « INVESTIGATING THE GROUND ENERGY DISTRIBUTION OF PARTICLES PRODUCED IN EXTENSIVE AIR SHOWERS ». Malaysian Journal of Science 41, n^o 2 (15 juin 2022) : 69–80. http://dx.doi.org/10.22452/mjs.vol41no2.6.

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The energy spectra of particle arrive the ground is a significant observable in the analysis of extensive air showers (EAS). The energy distribution at ground is studied for (12C,56Fe, p, and 28Si ) primary particles with high primary energies (1017, 1018, 1019 and 1020) eV with two zenith angles 0o and 30o. 960 EAS showers are simulated using Monte-Carlo program Aires version (19.04.00) with the models of hadronic interaction (EPOS-LHC, QGSJET-II-04, and Sibyll2.3c). In this study we investigated various secondary particles that arrive the ground and deposit a portion of their energy on ground detectors. The analyzed results show that the distinction in the energy distribution at ground is bigger for primary proton than carbon, iron nuclei, and silicon at higher energies and vertical showers.

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Boesch, H., N. M. Deutscher, T. Warneke, K. Byckling, A. J. Cogan, D. W. T. Griffith, J. Notholt, R. J. Parker et Z. Wang. « HDO/H2O ratio retrievals from GOSAT ». Atmospheric Measurement Techniques 6, n^o 3 (7 mars 2013) : 599–612. http://dx.doi.org/10.5194/amt-6-599-2013.

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Abstract. We report a new shortwave infrared (SWIR) retrieval of the column-averaged HDO/H2O ratio from the Japanese Greenhouse Gases Observing Satellite (GOSAT). From synthetic simulation studies, we have estimated that the inferred δD values will typically have random errors between 20‰ (desert surface and 30° solar zenith angle) and 120‰ (conifer surface and 60° solar zenith angle). We find that the retrieval will have a small but significant sensitivity to the presence of cirrus clouds, the HDO a priori profile shape and atmospheric temperature, which has the potential of introducing some regional-scale biases in the retrieval. From comparisons to ground-based column observations from the Total Carbon Column Observing Network (TCCON), we find differences between δD from GOSAT and TCCON of around −30‰ for northern hemispheric sites which increase up to −70‰ for Australian sites. The bias for the Australian sites significantly reduces when decreasing the spatial co-location criteria, which shows that spatial averaging contributes to the observed differences over Australia. The GOSAT retrievals allow mapping the global distribution of δD and its variations with season, and we find in our global GOSAT retrievals the expected strong latitudinal gradients with significant enhancements over the tropics. The comparisons to the ground-based TCCON network and the results of the global retrieval are very encouraging, and they show that δD retrieved from GOSAT should be a useful product that can be used to complement datasets from thermal-infrared sounder and ground-based networks and to extend the δD dataset from SWIR retrievals established from the recently ended SCIAMACHY mission.

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Boesch, H., N. M. Deutscher, T. Warneke, K. Byckling, A. J. Cogan, D. W. T. Griffith, J. Notholt, R. J. Parker et Z. Wang. « HDO/H2O ratio retrievals from GOSAT ». Atmospheric Measurement Techniques Discussions 5, n^o 5 (13 septembre 2012) : 6643–77. http://dx.doi.org/10.5194/amtd-5-6643-2012.

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Abstract. We report a new shortwave infrared (SWIR) retrieval of the column-averaged HDO/H2O ratio from the Japanese Greenhouse Gases Observing SATellite (GOSAT). From synthetic simulation studies, we have estimated that the inferred δD values will typically have random errors between 20‰ (desert surface and 30° solar zenith angle) and 120‰ (conifer surface and 60° solar zenith angle). We find that the retrieval will have a small, but significant sensitivity to the presence of cirrus clouds, the HDO a priori profile shape and atmospheric temperature, which has the potential for introducing some regional-scale biases in the retrieval. From comparisons to ground-based column observations from the Total Carbon Column Observing Network (TCCON) we find differences between δD from GOSAT and TCCON of around −30‰ for northern-hemispheric sites which increase up to −70‰ for Australian sites. The bias for the Australian sites significantly reduces when decreasing the spatial co-location criteria, which shows that spatial averaging contributes to the observed differences over Australia. The GOSAT retrievals allow mapping the global distribution of δD and its variations with season and we find in our global GOSAT retrievals the expected strong latitudinal gradients with significant enhancements over the tropics. The comparisons to the ground-based TCCON network and the results of the global retrieval are very encouraging and they show that δD retrieved from GOSAT should be a useful product that can be used to complement datasets from thermal-infrared sounder and ground-based networks and to extend the δD dataset from SWIR retrievals established from the recently ended SCIAMACHY mission.

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van Angelen, J. H., J. T. M. Lenaerts, S. Lhermitte, X. Fettweis, P. Kuipers Munneke, M. R. van den Broeke, E. van Meijgaard et C. J. P. P. Smeets. « Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization : a study with a regional climate model ». Cryosphere 6, n^o 5 (23 octobre 2012) : 1175–86. http://dx.doi.org/10.5194/tc-6-1175-2012.

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Abstract. We present a sensitivity study of the surface mass balance (SMB) of the Greenland Ice Sheet, as modeled using a regional atmospheric climate model, to various parameter settings in the albedo scheme. The snow albedo scheme uses grain size as a prognostic variable and further depends on cloud cover, solar zenith angle and black carbon concentration. For the control experiment the overestimation of absorbed shortwave radiation (+6%) at the K-transect (west Greenland) for the period 2004–2009 is considerably reduced compared to the previous density-dependent albedo scheme (+22%). To simulate realistic snow albedo values, a small concentration of black carbon is needed, which has strongest impact on melt in the accumulation area. A background ice albedo field derived from MODIS imagery improves the agreement between the modeled and observed SMB gradient along the K-transect. The effect of enhanced meltwater retention and refreezing is a decrease of the albedo due to an increase in snow grain size. As a secondary effect of refreezing the snowpack is heated, enhancing melt and further lowering the albedo. Especially in a warmer climate this process is important, since it reduces the refreezing potential of the firn layer that covers the Greenland Ice Sheet.

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Baker, D. F., H. Bösch, S. C. Doney, D. O'Brien et D. S. Schimel. « Carbon source/sink information provided by column CO2 ; measurements from the Orbiting Carbon Observatory ». Atmospheric Chemistry and Physics 10, n^o 9 (3 mai 2010) : 4145–65. http://dx.doi.org/10.5194/acp-10-4145-2010.

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Abstract. We quantify how well column-integrated CO2 measurements from the Orbiting Carbon Observatory (OCO) should be able to constrain surface CO2 fluxes, given the presence of various error sources. We use variational data assimilation to optimize weekly fluxes at a 2°×5° resolution (lat/lon) using simulated data averaged across each model grid box overflight (typically every ~33 s). Grid-scale simulations of this sort have been carried out before for OCO using simplified assumptions for the measurement error. Here, we more accurately describe the OCO measurements in two ways. First, we use new estimates of the single-sounding retrieval uncertainty and averaging kernel, both computed as a function of surface type, solar zenith angle, aerosol optical depth, and pointing mode (nadir vs. glint). Second, we collapse the information content of all valid retrievals from each grid box crossing into an equivalent multi-sounding measurement uncertainty, factoring in both time/space error correlations and data rejection due to clouds and thick aerosols. Finally, we examine the impact of three types of systematic errors: measurement biases due to aerosols, transport errors, and mistuning errors caused by assuming incorrect statistics. When only random measurement errors are considered, both nadir- and glint-mode data give error reductions over the land of ~45% for the weekly fluxes, and ~65% for seasonal fluxes. Systematic errors reduce both the magnitude and spatial extent of these improvements by about a factor of two, however. Improvements nearly as large are achieved over the ocean using glint-mode data, but are degraded even more by the systematic errors. Our ability to identify and remove systematic errors in both the column retrievals and atmospheric assimilations will thus be critical for maximizing the usefulness of the OCO data.

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Hsü, K. J. « Is Gaia endothermic ? » Geological Magazine 129, n^o 2 (mars 1992) : 129–41. http://dx.doi.org/10.1017/s0016756800008232.

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AbstractGeological evidence suggests that Gaia is endothermic: her body temperature has varied, but within limits; there has been no runaway greenhouse like Venus, nor deep freeze like Mars. This paper presents a hypothesis that the Earth's climate has been ameliorated by living organisms: they have served either as heaters or air-conditioners, and their ecological tolerance is the sensor of Gaia's thermostat. At the beginning, 3.8 or 3.5 Ga ago, only anaerobic autotrophs capable of tolerating high temperatures thinned out the atmospheric CO2 through carbon fixation. Fossil organic carbon was utilized by anaerobic heterotrophs to reinforce the effectiveness of the late Archean greenhouse, when solar luminosity was weaker than it is now. With the increasing solar luminosity during early Proterozoic time, new life forms such as cyanobacteria evolved, removing CO2 from the atmosphere and storing it in stromatolitic carbonates. Over-eager cyanobacteria may have consumed too much greenhouse CO2 to cause glaciation. Their decline coincided in timing with the rise of the Ediacaran faunas which had no carbonate skeletons. The change in the mode of carbon-cycling may have started the warming trend after the Proterozoic glaciation. The Cambrian explosion was an event when skeletal eukaryotes usurped the function of prokaryotes in removing greenhouse CO2 through CaCO3 precipitation. With the evolution of land plants, coal-makers took over the ‘air-conditioning’ duty. They over-did it, and Permo-Carboniferous glaciation ensued. After a wholesale turnover of the faunas and floras at the end of the Palaeozoic, more CO2 was released than fixed in early Mesozoic time. The warming trend reached its zenith in the early Cretaceous, when flowering trees and calcareous plankton began to flourish. The decline since then, with a temporary restoration during early Palaeogene time, could be a manifestation of the varying efficiency of extracting and burying carbon dioxide, in the form of inorganic and organic carbon. The relation of atmospheric CO2 and climatic variation is documented by study of air bubbles in ice cores. Yet there is also correlation to astronomical cycles. The latter seem to have triggered changes which are amplified by feedback mechanisms of carbon cycling.

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Gul, Chaman, Siva Praveen Puppala, Shichang Kang, Bhupesh Adhikary, Yulan Zhang, Shaukat Ali, Yang Li et Xiaofei Li. « Concentrations and source regions of light-absorbing particles in snow/ice in northern Pakistan and their impact on snow albedo ». Atmospheric Chemistry and Physics 18, n^o 7 (12 avril 2018) : 4981–5000. http://dx.doi.org/10.5194/acp-18-4981-2018.

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Abstract. Black carbon (BC), water-insoluble organic carbon (OC), and mineral dust are important particles in snow and ice which significantly reduce albedo and accelerate melting. Surface snow and ice samples were collected from the Karakoram–Himalayan region of northern Pakistan during 2015 and 2016 in summer (six glaciers), autumn (two glaciers), and winter (six mountain valleys). The average BC concentration overall was 2130 ± 1560 ng g−1 in summer samples, 2883 ± 3439 ng g−1 in autumn samples, and 992 ± 883 ng g−1 in winter samples. The average water-insoluble OC concentration overall was 1839 ± 1108 ng g−1 in summer samples, 1423 ± 208 ng g−1 in autumn samples, and 1342 ± 672 ng g−1 in winter samples. The overall concentration of BC, OC, and dust in aged snow samples collected during the summer campaign was higher than the concentration in ice samples. The values are relatively high compared to reports by others for the Himalayas and the Tibetan Plateau. This is probably the result of taking more representative samples at lower elevation where deposition is higher and the effects of ageing and enrichment are more marked. A reduction in snow albedo of 0.1–8.3 % for fresh snow and 0.9–32.5 % for aged snow was calculated for selected solar zenith angles during daytime using the Snow, Ice, and Aerosol Radiation (SNICAR) model. The daily mean albedo was reduced by 0.07–12.0 %. The calculated radiative forcing ranged from 0.16 to 43.45 W m−2 depending on snow type, solar zenith angle, and location. The potential source regions of the deposited pollutants were identified using spatial variance in wind vector maps, emission inventories coupled with backward air trajectories, and simple region-tagged chemical transport modeling. Central, south, and west Asia were the major sources of pollutants during the sampling months, with only a small contribution from east Asia. Analysis based on the Weather Research and Forecasting (WRF-STEM) chemical transport model identified a significant contribution (more than 70 %) from south Asia at selected sites. Research into the presence and effect of pollutants in the glaciated areas of Pakistan is economically significant because the surface water resources in the country mainly depend on the rivers (the Indus and its tributaries) that flow from this glaciated area.

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Baker, D. F., H. Bösch, S. C. Doney et D. S. Schimel. « Carbon source/sink information provided by column CO2 ; measurements from the Orbiting Carbon Observatory ». Atmospheric Chemistry and Physics Discussions 8, n^o 6 (28 novembre 2008) : 20051–112. http://dx.doi.org/10.5194/acpd-8-20051-2008.

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Abstract. We perform a series of observing system simulation experiments (OSSEs) to quantify how well surface CO2 fluxes may be estimated using column-integrated CO2 data from the Orbiting Carbon Observatory (OCO), given the presence of various error sources. We use variational data assimilation to optimize weekly fluxes at 2°×5° (lat/lon) using simulated data averaged only across the ~33 s that OCO takes to cross a typical 2°×5° model grid box. Grid-scale OSSEs of this sort have been carried out before for OCO using simplified assumptions for the measurement error. Here, we more accurately describe the OCO measurements in two ways. First, we use new estimates of the single-sounding retrieval uncertainty and averaging kernel, both computed as a function of surface type, solar zenith angle, aerosol optical depth, and pointing mode (nadir vs. glint). Second, we collapse the information content of all valid retrievals from each grid box crossing into an equivalent multi-sounding measurement uncertainty, factoring in both time/space error correlations and data availability due to clouds and thick aerosols (calculated from MODIS data). Finally, we examine the impact of three types of systematic errors: measurement biases due to aerosols, transport errors, and errors caused by assuming incorrect error statistics. When only random measurement errors are considered, both nadir- and glint-mode data give error reductions of ~50% over the land for the weekly fluxes, and ~65% for seasonal fluxes. Systematic errors reduce both the magnitude and extent of these improvements by up to a factor of two, however. Flux improvements over the ocean are significant only when using glint-mode data and are smaller than those over land; when the assimilation is mistuned, slow convergence makes even these improvements difficult to achieve. The OCO data may prove most useful over the tropical land areas, where our current flux knowledge is weak and where the measurements remain fairly accurate even in the face of systematic errors.

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Rohlffs, Fiona, Nikolaos Tsilimparis, Constantin Trepte, Jarin Kratzberg, John Mogensen, E. Sebastian Debus et Tilo Kölbel. « Air Embolism During TEVAR : An Additional Flush Port on the Delivery System Pusher Significantly Reduces the Amount of Air Released During Deployment of a Thoracic Stent-Graft in an Experimental Setting ». Journal of Endovascular Therapy 25, n^o 4 (5 juin 2018) : 435–39. http://dx.doi.org/10.1177/1526602818780951.

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Purpose: To investigate the influence of (1) an additional side port for flushing the hollow pusher in Zenith thoracic stent-graft delivery systems and (2) additional carbon dioxide flushing on the amount of air released during stent-graft deployment. Methods: Twenty thoracic stent-grafts with an additional flush port to fill the hollow pusher were separated into 2 equal groups (C and D). Both groups were flushed with 20 mL of normal saline through the extra side port connected to the pusher and with 60 mL of saline through the regular flushing port. One group of grafts (group D) was additionally flushed with carbon dioxide through the regular flushing port prior to saline. All grafts were deployed into a curved plastic pipe attached to the bottom of a water-filled container. The released gas was recorded and measured using a calibrated setup. To evaluate the influence of the extra side port irrespective of the carbon dioxide flushing technique, group C was compared with a previously published reference group A without an extra side port that was flushed with the standard 60 mL of saline. Results: Volumes of gas were released in various amounts from the stent-grafts during deployment. The average amount of released gas was 0.51 mL in group C and 0.07 mL in group D (p<0.001). The mean amount of gas from group C samples (0.51 mL) was also significantly lower (p=0.002) compared with the reference group (0.79 mL). Conclusion: Thoracic endografts release air during deployment. Reducing the air-filled space inside the pusher of the catheter assembly using an additional side port can significantly reduce the amount of released air. Using the extra side port in combination with the carbon dioxide flushing technique reduces gas release further to small volumes. In a clinical setting this could be a promising approach to lower the risk of air embolism and stroke during thoracic endovascular aortic repair.

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Landgraf, Jochen, Joost aan de Brugh, Remco Scheepmaker, Tobias Borsdorff, Haili Hu, Sander Houweling, Andre Butz, Ilse Aben et Otto Hasekamp. « Carbon monoxide total column retrievals from TROPOMI shortwave infrared measurements ». Atmospheric Measurement Techniques 9, n^o 10 (7 octobre 2016) : 4955–75. http://dx.doi.org/10.5194/amt-9-4955-2016.

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Abstract. The Tropospheric Monitoring Instrument (TROPOMI) spectrometer is the single payload of the Copernicus Sentinel 5 Precursor (S5P) mission. It measures Earth radiance spectra in the shortwave infrared spectral range around 2.3 µm with a dedicated instrument module. These measurements provide carbon monoxide (CO) total column densities over land, which for clear sky conditions are highly sensitive to the tropospheric boundary layer. For cloudy atmospheres over land and ocean, the column sensitivity changes according to the light path through the atmosphere. In this study, we present the physics-based operational S5P algorithm to infer atmospheric CO columns satisfying the envisaged accuracy ( < 15 %) and precision ( < 10 %) both for clear sky and cloudy observations with low cloud height. Here, methane absorption in the 2.3 µm range is combined with methane abundances from a global chemical transport model to infer information on atmospheric scattering. For efficient processing, we deploy a linearized two-stream radiative transfer model as forward model and a profile scaling approach to adjust the CO abundance in the inversion. Based on generic measurement ensembles, including clear sky and cloudy observations, we estimated the CO retrieval precision to be ≤ 11 % for surface albedo ≥ 0.03 and solar zenith angle ≤ 70°. CO biases of ≤ 3 % are introduced by inaccuracies in the methane a priori knowledge. For strongly enhanced CO concentrations in the tropospheric boundary layer and for cloudy conditions, CO errors in the order of 8 % can be introduced by the retrieval of cloud parameters of our algorithm. Moreover, we estimated the effect of a distorted spectral instrument response due to the inhomogeneous illumination of the instrument entrance slit in the flight direction to be < 2 % with pseudo-random characteristics when averaging over space and time. Finally, the CO data exploitation is demonstrated for a TROPOMI orbit of simulated shortwave infrared measurements. Overall, the study demonstrates that for an instrument that performs in compliance with the pre-flight specifications, the CO product will meet the required product performance well.

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Mendonca, Joseph, Kimberly Strong, Debra Wunch, Geoffrey C. Toon, David A. Long, Joseph T. Hodges, Vincent T. Sironneau et Jonathan E. Franklin. « Using a speed-dependent Voigt line shape to retrieve O2 ; from Total Carbon Column Observing Network solar spectra to improve measurements of XCO2 ; ». Atmospheric Measurement Techniques 12, n^o 1 (3 janvier 2019) : 35–50. http://dx.doi.org/10.5194/amt-12-35-2019.

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Abstract. High-resolution, laboratory, absorption spectra of the a1Δg←X3Σg- oxygen (O2) band measured using cavity ring-down spectroscopy were fitted using the Voigt and speed-dependent Voigt line shapes. We found that the speed-dependent Voigt line shape was better able to model the measured absorption coefficients than the Voigt line shape. We used these line shape models to calculate absorption coefficients to retrieve atmospheric total columns abundances of O2 from ground-based spectra from four Fourier transform spectrometers that are a part of the Total Carbon Column Observing Network (TCCON). Lower O2 total columns were retrieved with the speed-dependent Voigt line shape, and the difference between the total columns retrieved using the Voigt and speed-dependent Voigt line shapes increased as a function of solar zenith angle. Previous work has shown that carbon dioxide (CO2) total columns are better retrieved using a speed-dependent Voigt line shape with line mixing. The column-averaged dry-air mole fraction of CO2 (XCO2) was calculated using the ratio between the columns of CO2 and O2 retrieved (from the same spectra) with both line shapes from measurements taken over a 1-year period at the four sites. The inclusion of speed dependence in the O2 retrievals significantly reduces the air mass dependence of XCO2, and the bias between the TCCON measurements and calibrated integrated aircraft profile measurements was reduced from 1 % to 0.4 %. These results suggest that speed dependence should be included in the forward model when fitting near-infrared CO2 and O2 spectra to improve the accuracy of XCO2 measurements.

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Tian, Shihao, Guang Zheng, Jan U. Eitel et Qian Zhang. « A Lidar-Based 3-D Photosynthetically Active Radiation Model Reveals the Spatiotemporal Variations of Forest Sunlit and Shaded Leaves ». Remote Sensing 13, n^o 5 (6 mars 2021) : 1002. http://dx.doi.org/10.3390/rs13051002.

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Accurately identifying sunlit and shaded leaves using process-based ecological models can improve the simulation accuracy of forest photosynthetic rates and potential carbon sequestration capacity. However, it is still challenging to characterize their three dimensional (3-D) spatiotemporal distributions due to the complex structure. In this study, we developed a light detection and ranging (lidar)-based approach to map the spatiotemporal distribution patterns of photosynthetically active radiation (PAR) and sunlit and shaded leaves within forest canopies. By using both terrestrial laser scanning (TLS) and unmanned aerial vehicle-based lidar system (UAV-LS), we analyzed the influences of different scanning geometries and associated point densities on the separation of sunlit and shaded leaves. Moreover, we further investigated the effects of woody materials and penumbra sizes on identifying sunlit and shaded leaves by separating the foliage and woody materials and estimating the penumbras of sunlit leaves. Our results showed that: (1) The proposed lidar-based PAR model could well capture the variations of field-based pyranometer measurements using fused point data by combining UAV-LS and TLS data (mean R-square = 0.88, mean root mean square error (RMSE) = 155.5 μmol·m−2·s−1, p < 0.01). The separate UAV-LS and TLS-based fractions of sunlit leaves were averagely overestimated by 34.3% and 21.6% when compared to the fused point data due to their different coverages and comprehensiveness. (2) The woody materials showed different effects on sunlit leaf fraction estimations for forest overstory and understory due to the variations of solar zenith angle and tree spatial distribution patterns. The most noticeable differences (i.e., −36.4%) between the sunlit leaf fraction before and after removing woody materials were observed around noon, with a small solar zenith angle and low-density forest stand. (3) The penumbra effects were seen to increase the sunlit leaf fraction in the lower canopy by introducing direct solar radiation, and it should be considered when using 3-D structural information from lidar to identify sunlit and shaded leaves.

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He, Zijing, Simei Lin, Kunjian Wen, Wenqian Hao et Ling Chen. « Effects of Mixture Mode on the Canopy Bidirectional Reflectance of Coniferous–Broadleaved Mixed Plantations ». Forests 13, n^o 2 (3 février 2022) : 235. http://dx.doi.org/10.3390/f13020235.

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One of the main initiatives for China to achieve the goal of being carbon neutral before 2060 is transforming monocultures into mixed plantations in subtropical China, because mixed forests possess a higher quality than monocultures in various ways. Very high spatial resolution (VHR) satellite imagery is very promising to precisely monitor the transformation process under the premise of clarifying the canopy reflectance anisotropy of mixed plantations. However, it is almost impossible to understand the canopy reflectance anisotropy of mixed plantations with real satellite data due to the extreme lack of multiangular VHR satellite images. In this study, the effects of the mixture mode on the canopy bidirectional reflectance factor (BRF) were comprehensively analyzed with simulated VHR images. The three-dimensional (3D) Discrete Anisotropic Radiative Transfer model (DART) was used to construct a pure coniferous scene, a pure broadleaved scene, and 27 coniferous–broadleaved mixed plantation scenes containing 3 mixture patterns (i.e., mixed by single trees, mixed by stripes, and mixed by patches) and 9 mixing proportions (i.e., from 10% to 90% with the interval of 10%), and to simulate red (R) and near-infrared (NIR) VHR images for these 3D scenes at both the solar principal plane (SPP) and perpendicular plane (PP) under different solar-viewing geometries. Negative correlations were generally found between the canopy BRF and the ratio of conifers in a mixed stand. The anisotropy of conifer dominated plantations is more prominent than broadleaf dominated plantations, especially for the single tree mixture. Although the level of anisotropy is much lower for PP than SPP, it should not be ignored, especially for the R band. Observations under large viewing zenith angles at PP are more preferred to study the effect of mixing proportions, followed by forward observations at SPP. The R band image has higher potential to distinguish mixture patterns for broadleaf-dominated situations, while the NIR band image has a higher potential for conifer-dominated situations. Furthermore, the canopy BRF generally increases with the solar zenith angle, and one meter can be considered as the optimal spatial resolution for the optical monitoring of the mixture mode. The findings of the current study add some valuable theoretical knowledge for the accurate monitoring of coniferous–broadleaved mixed plantations with VHR imagery.

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Espey, Brian R. « Empirical Modelling of Public Lighting Emission Functions ». Remote Sensing 13, n^o 19 (24 septembre 2021) : 3827. http://dx.doi.org/10.3390/rs13193827.

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Study of light at night has increased in recent decades due to the recognition of its impact on the environment, potential health concerns, as well as both the financial and carbon cost of energy waste. The advent of more extensive and improved ground-based measurements together with quantifiable satellite data has revolutionised the field, and provided data to test improved theoretical models. However, “closing the loop” and finding a detailed connection between these measurements requires knowledge of the “city emission function”, the angular distribution of upwelling radiation with zenith distance. Simplified analytical functions have been superseded by more complex models involving statistical approximation of emission sources and obstructions and inversion techniques now permit the estimation of emission functions from the observed sky brightness measurements. In this paper, we present an efficient GIS-based method to model public lighting using real-world photometric data and high-resolution digital elevation maps of obstructions such as buildings and trees at a 1 m scale. We discuss the results of this work for a sample of Irish towns as well as a city area. We also compare our results to previous emission functions as well as to observed asymmetries in emission detected by satellites such as SUOMI VIIRS.

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Powers, S. K., R. E. Beadle, D. Thompson et J. Lawler. « Ventilatory and blood gas dynamics at onset and offset of exercise in the pony ». Journal of Applied Physiology 62, n^o 1 (1 janvier 1987) : 141–48. http://dx.doi.org/10.1152/jappl.1987.62.1.141.

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The purpose of these experiments was to examine the temporal pattern of arterial carbon dioxide tension (PaCO2) to assess the relationship between alveolar ventilation (VA) and CO2 return to the lung at the onset and offset of submaximal treadmill exercise. Five healthy ponies exercised for 8 min at two work rates: 50 m/min 6% grade and 70 m/min 12% grade. PaCO2 decreased (P less than 0.05) below resting values within 1 min after commencement of exercise at both work rates and reached a nadir at 90 s. PaCO2 decreased maximally by 2.5 and 3.5 Torr at the low and moderate rate, respectively. After the nadir, PaCO2 increased across time during both work rates and reached values that were not significantly different (P greater than 0.05) from rest at minute 4 of exercise. Partial pressure of O2 in arterial blood and arterial pH reflected hyperventilation during the first 3 min of exercise. At the termination of exercise PaCO2 increased (1.5 Torr) above rest (P less than 0.05), reaching a zenith at 2–3 min of recovery. These data suggest that VA and CO2 flow to the lung are not tightly matched at the onset and offset of exercise in the pony and thus challenges the traditional concept of blood gas homeostasis during muscular exercise.

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Nivitanont, Jeffrey, Sean M. R. Crowell et Berrien Moore III. « A scanning strategy optimized for signal-to-noise ratio for the Geostationary Carbon Cycle Observatory (GeoCarb) instrument ». Atmospheric Measurement Techniques 12, n^o 6 (21 juin 2019) : 3317–34. http://dx.doi.org/10.5194/amt-12-3317-2019.

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Abstract. The Geostationary Carbon Cycle Observatory (GeoCarb) will make measurements of greenhouse gases over the contiguous North and South American landmasses at daily temporal resolution. The extreme flexibility of observing from geostationary orbit induces an optimization problem, as operators must choose what to observe and when. The proposed scanning strategy for the GeoCarb mission tracks the sun's path from east to west and covers the entire area of interest in five coherent regions in the order of tropical South America east, tropical South America west, temperate South America, tropical North America, and temperate North America. We express this problem in terms of a geometric set cover problem, and use an incremental optimization (IO) algorithm to create a scanning strategy that minimizes expected error as a function of the signal-to-noise ratio (SNR). The IO algorithm used in this studied is a modified greedy algorithm that selects, incrementally at 5 min intervals, the scanning areas with the highest predicted SNR with respect to air mass factor (AF) and solar zenith angle (SZA) while also considering operational constraints to minimize overlapping scans and observations over water. As a proof of concept, two experiments are performed applying the IO algorithm offline to create an SNR-optimized strategy and compare it to the proposed strategy. The first experiment considers all landmasses with equal importance and the second experiment illustrates a temporary campaign mode that gives major urban areas greater importance weighting. Using a simple instrument model, we found that there is a significant performance increase with respect to overall predicted error when comparing the algorithm-selected scanning strategies to the proposed scanning strategy.

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Richardson, Mark, Matthew D. Lebsock, James McDuffie et Graeme L. Stephens. « A new Orbiting Carbon Observatory 2 cloud flagging method and rapid retrieval of marine boundary layer cloud properties ». Atmospheric Measurement Techniques 13, n^o 9 (18 septembre 2020) : 4947–61. http://dx.doi.org/10.5194/amt-13-4947-2020.

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Abstract. The Orbiting Carbon Observatory 2 (OCO-2) carries a hyperspectral A-band sensor that can obtain information about cloud geometric thickness (H). The OCO2CLD-LIDAR-AUX product retrieved H with the aid of collocated CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) lidar data to identify suitable clouds and provide a priori cloud top pressure (Ptop). This collocation is no longer possible, since CALIPSO's coordination flying with OCO-2 has ended, so here we introduce a new cloud flagging and a priori assignment using only OCO-2 data, restricted to ocean footprints where solar zenith angle <45∘. Firstly, a multi-layer perceptron network was trained to identify liquid clouds over the ocean with sufficient optical depth (τ>1) for a valid retrieval, and agreement with MODIS–CALIPSO (Moderate Resolution Imaging Spectroradiometer) is 90.0 %. Secondly, we developed a lookup table to simultaneously retrieve cloud τ, effective radius (re) and Ptop from A-band and CO2 band radiances, with the intention that these will act as the a priori state estimate in a future retrieval. Median Ptop difference vs. CALIPSO is 12 hPa with an inter-decile range of [-11,87]hPa, substantially better than the MODIS–CALIPSO range of [-83,81]hPa. The MODIS–OCO-2 τ difference is 0.8[-3.8,6.9], and re is -0.3[-2.8,2.1]µm. The τ difference is due to optically thick and horizontally heterogeneous cloud scenes. As well as an improved passive Ptop retrieval, this a priori information will allow for a purely OCO-2-based Bayesian retrieval of cloud droplet number concentration (Nd). Finally, our cloud flagging procedure may also be useful for future partial-column above-cloud CO2 abundance retrievals.

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Yurganov, L., W. McMillan, C. Wilson, M. Fischer, S. Biraud et C. Sweeney. « Carbon monoxide mixing ratios over Oklahoma between 2002 and 2009 retrieved from Atmospheric Emitted Radiance Interferometer spectra ». Atmospheric Measurement Techniques 3, n^o 5 (5 octobre 2010) : 1319–31. http://dx.doi.org/10.5194/amt-3-1319-2010.

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Abstract. CO mixing ratios for the lowermost 2-km atmospheric layer were retrieved from downwelling infrared (IR) radiance spectra of the clear sky measured between 2002 and 2009 by a zenith-viewing Atmospheric Emitted Radiance Interferometer (AERI) deployed at the Southern Great Plains (SGP) observatory of the Atmospheric Radiation Measurements (ARM) Program near Lamont, Oklahoma. A version of a published earlier retrieval algorithm was improved and validated. Archived temperature and water vapor profiles retrieved from the same AERI spectra through automated ARM processing were used as input data for the CO retrievals. We found the archived water vapor profiles required additional constraint using SGP Microwave Radiometer retrievals of total precipitable water vapor. A correction for scattered solar light was developed as well. The retrieved CO was validated using simultaneous independently measured CO profiles from an aircraft. These tropospheric CO profiles were measured from the surface to altitudes of 4572 m a.s.l. once or twice a week between March 2006 and December 2008. The aircraft measurements were supplemented with ground-based CO measurements using a non-dispersive infrared gas correlation instrument at the SGP and retrievals from the Atmospheric IR Sounder (AIRS) above 5 km to create full tropospheric CO profiles. Comparison of the profiles convolved with averaging kernels to the AERI CO retrievals found a squared correlation coefficient of 0.57, a standard deviation of ±11.7 ppbv, a bias of -16 ppbv, and a slope of 0.92. Averaged seasonal and diurnal cycles measured by the AERI are compared with those measured continuously in situ at the SGP in the boundary layer. Monthly mean CO values measured by the AERI between 2002 and 2009 are compared with those measured by the AIRS over North America, the Northern Hemisphere mid-latitudes, and over the tropics.

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Zou, X., X. Zhuge et F. Weng. « Characterization of Bias of Advanced Himawari Imager Infrared Observations from NWP Background Simulations Using CRTM and RTTOV ». Journal of Atmospheric and Oceanic Technology 33, n^o 12 (décembre 2016) : 2553–67. http://dx.doi.org/10.1175/jtech-d-16-0105.1.

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AbstractStarting in 2014, the new generation of Japanese geostationary meteorological satellites carries an Advanced Himawari Imager (AHI) to provide the observations of visible, near infrared, and infrared with much improved spatial and temporal resolutions. For applications of the AHI measurements in numerical weather prediction (NWP) data assimilation systems, the biases of the AHI brightness temperatures at channels 7–16 from the model simulations are first characterized and evaluated using both the Community Radiative Transfer Model (CRTM) and the Radiative Transfer for the TIROS Operational Vertical Sounder (RTTOV). It is found that AHI biases under a clear-sky atmosphere are independent of satellite zenith angle except for channel 7. The biases of three water vapor channels increase with scene brightness temperatures and are nearly constant except at high brightness temperatures for the remaining infrared channels. The AHI biases at all the infrared channels are less than 0.6 and 1.2 K over ocean and land, respectively. The differences in biases between RTTOV and CRTM with the land surface emissivity model used in RTTOV are small except for the upper-tropospheric water vapor channels 8 and 9 and the low-tropospheric carbon dioxide channel 16. Since the inputs used for simulations are the same for CRTM and RTTOV, the differential biases at the water vapor channels may be associated with subtle differences in forward models.

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Chen, H. H., W. C. Chao, Y. H. Chen, D. Y. Chen et C. H. Lin. « FRI0531 AIR POLLUTANTS AND DEVELOPMENT OF INTERSTITIAL LUNG DISEASE IN PATIENTS WITH AUTOIMMUNE DISEASES ». Annals of the Rheumatic Diseases 79, Suppl 1 (juin 2020) : 865.1–865. http://dx.doi.org/10.1136/annrheumdis-2020-eular.204.

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Background:Interstitial lung disease (ILD) is characterized by progressive inflammation and fibrosis, and accumulating evidence have shown that exposure to air pollutants was associated with the development of ILD. Autoimmune diseases are highly correlated with ILD, including connective tissue disease-associated ILD (CTD-ILD) as well as interstitial pneumonia with autoimmune features (IPAF), and the development of ILD is a crucial cause of morbidity and mortality in patients with autoimmune diseases. One recent Taiwanese study reported that exposure to air pollutants was associated with incident systemic lupus erythematosus (SLE). However, the impact of air pollutants on the development of ILD among patients with autoimmune diseases remains unknown.Objectives:The study aimed to address the impact of accumulating exposure to air pollutant above moderate level, defined by Air Quality Index (AQI) value higher than 50, on the development of ILD in patients with autoimmune diseases including SLE, rheumatoid arthritis (RA) and primary Sjögren’s syndrome (SS).Methods:We used a National Health Insurance Research Database in Taiwan to enroll patients with SLE (International Classification of Diseases (ICD)-9 code 710.0, n=13,211), RA (ICD-9 code 714.0 and 714.30–714.33, n=32,373), and primary SS (ICD-9 code, 710.0, n=15,246) between 2001 and 2013. We identified newly diagnosed ILD cases (ICD-code 515) between 2012 and 2013 and selected age, sex, disease duration and index-year matched (1:4) patients as non-ILD controls. The hourly levels of air pollutants one year prior to the index-date were obtained from 60 air quality monitoring stations across Taiwan, and the air pollutants in the present study consisted of particulate matter <2.5 μm in size (PM2.5), particulate matter <10 μm in size (PM10), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2) and ozone (O3). We used a spatio-temporal model built by a deep-learning mechanism to estimate levels of air pollutants at 374 residential locations based on data of 3 air quality monitoring stations near the location (8). Notably, we used cumulative exposed hours to air pollutants higher than modest level, defined by AQI criteria, given that daily mean level of air pollutants might possibly underestimate the triggered inflammatory effect by a temporary exposure of high-level air pollutant. A conditional logistic regression was used to determine the association between exposure to air pollutant and the development of ILD, adjusting age, gender, Charlson Comorbidity Index (CCI), urbanization, family income, and medications for autoimmune diseases.Results:A total of 272 patients with newly diagnosed ILD were identified among patients with autoimmune diseases, including 39 with SLE, 135 with RA, and 98 with primary SS. We found that the duration of exposure to PM 2.5 higher than modest level was associated with the risk of ILD development in patients with SS (adjOR 1.07, 95% CI 1.01–1.13), and similar trends were also found in patients with SLE (adjOR 1.03, 95% CI 0.95–1.12) and RA (adjOR 1.03, 95% CI 0.99–1.07). Intriguingly, we observed an inverse correlation between the duration of exposure to O3 and the development of ILD in patients with SS (adjOR 0.83, 95% CI 0.70–0.99); however, the finding was not found in patients with SLE (adjOR 1.13, 95% CI 0.92–1.37) and RA (adjOR 0.98, 95% CI 0.87–1.11).Conclusion:In conclusion, we identified that longer exposure to PM2.5 higher than modest level tended to be associated with the development of ILD in patients with autoimmune diseases, mainly SS.References:[1] Araki T, Putman RK, Hatabu H, Gao W, Dupuis J, Latourelle JC, et al. Development and Progression of Interstitial Lung Abnormalities in the Framingham Heart Study. Am J Respir Crit Care Med 2016;194:1514-1522.[2] Tang KT, Tsuang BJ, Ku KC, Chen YH, Lin CH, Chen DY. Relationship between exposure to air pollutants and development of systemic autoimmune rheumatic diseases: a nationwide population-based case-control study. Ann Rheum Dis 2019;78:1288-1291.Disclosure of Interests:Hsin-Hua Chen: None declared, Wen-Cheng Chao: None declared, Yi-Hsing Chen Grant/research support from: Taiwan Ministry of Science and Technology, Taiwan Department of Health, Taichung Veterans General Hospital, National Yang-Ming University, GSK, Pfizer, BMS., Consultant of: Pfizer, Novartis, Abbvie, Johnson & Johnson, BMS, Roche, Lilly, GSK, Astra& Zeneca, Sanofi, MSD, Guigai, Astellas, Inova Diagnostics, UCB, Agnitio Science Technology, United Biopharma, Thermo Fisher, Gilead., Paid instructor for: Pfizer, Novartis, Johnson & Johnson, Roche, Lilly, Astra& Zeneca, Sanofi, Astellas, Agnitio Science Technology, United Biopharma., Speakers bureau: Pfizer, Novartis, Abbvie, Johnson & Johnson, BMS, Roche, Lilly, GSK, Astra& Zeneca, Sanofi, MSD, Guigai, Astellas, Inova Diagnostics, UCB, Agnitio Science Technology, United Biopharma, Thermo Fisher, Gilead., Der-Yuan Chen: None declared, Ching-Heng Lin: None declared

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Flanner, Mark G., Julian B. Arnheim, Joseph M. Cook, Cheng Dang, Cenlin He, Xianglei Huang, Deepak Singh, S. McKenzie Skiles, Chloe A. Whicker et Charles S. Zender. « SNICAR-ADv3 : a community tool for modeling spectral snow albedo ». Geoscientific Model Development 14, n^o 12 (21 décembre 2021) : 7673–704. http://dx.doi.org/10.5194/gmd-14-7673-2021.

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Abstract. The Snow, Ice, and Aerosol Radiative (SNICAR) model has been used in various capacities over the last 15 years to model the spectral albedo of snow with light-absorbing constituents (LACs). Recent studies have extended the model to include an adding-doubling two-stream solver and representations of non-spherical ice particles; carbon dioxide snow; snow algae; and new types of mineral dust, volcanic ash, and brown carbon. New options also exist for ice refractive indices and solar-zenith-angle-dependent surface spectral irradiances used to derive broadband albedo. The model spectral range was also extended deeper into the ultraviolet for studies of extraterrestrial and high-altitude cryospheric surfaces. Until now, however, these improvements and capabilities have not been merged into a unified code base. Here, we document the formulation and evaluation of the publicly available SNICAR-ADv3 source code, web-based model, and accompanying library of constituent optical properties. The use of non-spherical ice grains, which scatter less strongly into the forward direction, reduces the simulated albedo perturbations from LACs by ∼9 %–31 %, depending on which of the three available non-spherical shapes are applied. The model compares very well against measurements of snow albedo from seven studies, though key properties affecting snow albedo are not fully constrained with measurements, including ice effective grain size of the top sub-millimeter of the snowpack, mixing state of LACs with respect to ice grains, and site-specific LAC optical properties. The new default ice refractive indices produce extremely high pure snow albedo (>0.99) in the blue and ultraviolet part of the spectrum, with such values only measured in Antarctica so far. More work is needed particularly in the representation of snow algae, including experimental verification of how different pigment expressions and algal cell concentrations affect snow albedo. Representations and measurements of the influence of liquid water on spectral snow albedo are also needed.

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Yurganov, L., W. McMillan, C. Wilson, M. Fischer et S. Biraud. « Carbon monoxide mixing ratios over Oklahoma between 2002 and 2009 retrieved from Atmospheric Emitted Radiance Interferometer spectra ». Atmospheric Measurement Techniques Discussions 3, n^o 2 (29 mars 2010) : 1263–301. http://dx.doi.org/10.5194/amtd-3-1263-2010.

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Abstract. CO mixing ratios weighted over the bottom 2-km thick atmospheric layer between 2002 and 2009 were retrieved from downwelling infrared (IR) radiance spectra of the clear sky measured by a zenith-viewing Atmospheric Emitted Radiance Interferometer (AERI) deployed at the Southern Great Plains (SGP) observatory of the Atmospheric Radiation Measurements (ARM) Program near Lamont, Oklahoma. A version of the algorithm proposed by He at al. (2001) was significantly improved and validated. Essentially, the new algorithm retrieves a CO mixing ratio that is determined by the convolution of the a priori profile (assumed to be constant with altitude), the true profile, and the averaging kernel which maximizes near the surface. Approximately 70% of the CO signal comes from the boundary layer and the remaining 30% come from the lower part of the free troposphere. Archived temperature and water vapor profiles retrieved from the same AERI spectra through automated ARM processing were used as input data for the CO retrievals. We found the archived water vapor profiles required additional constraint using SGP Microwave Radiometer retrievals of total precipitable water vapor. Additionally, a correction for scattered solar light was developed. The retrieved CO was validated using simultaneous independently measured CO profiles. An aircraft supplied in situ CO measurements at altitudes up to 4572 m above sea level once or twice a week between March 2006 and December 2008. The aircraft measurements were supplemented with ground-based CO measurements at the SGP and retrievals from the Atmospheric IR Sounder (AIRS) above 5 km to create full tropospheric CO profiles. Comparison of the convolved profiles to the AERI CO retrievals found a squared correlation coefficient of 0.57, a standard deviation of ±11.7 ppbv, a bias of 16 ppbv, and a slope of 0.92. Averaged seasonal and diurnal cycles measured by AERI are compared with those measured continuously in situ at the SGP in the boundary layer. Monthly mean CO values measured by AERI between 2002 and 2009 are compared with those measured by AIRS over North America, the Northern Hemisphere mid-latitudes, and over the tropics.

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de Foy, B., W. Lei, M. Zavala, R. Volkamer, J. Samuelsson, J. Mellqvist, B. Galle, A. P. Martínez, M. Grutter et L. T. Molina. « Modelling constraints on the emission inventory and on vertical diffusion for CO and SO2 ; in the Mexico City Metropolitan Area using Solar FTIR and zenith sky UV spectroscopy ». Atmospheric Chemistry and Physics Discussions 6, n^o 4 (11 juillet 2006) : 6125–81. http://dx.doi.org/10.5194/acpd-6-6125-2006.

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Abstract. Emissions of air pollutants in and around urban areas lead to negative health impacts on the population. To estimate these impacts, it is important to know the sources and transport mechanisms of the pollutants accurately. Mexico City has a large urban fleet in a topographically constrained basin leading to high levels of carbon monoxide (CO). Large point sources of sulfur dioxide (SO2) surrounding the basin lead to episodes with high concentrations. An Eulerian grid model (CAMx) and a particle trajectory model (FLEXPART) are used to evaluate the estimates of CO and SO2 in the current emission inventory using mesoscale meteorological simulations from MM5. Vertical column measurements of CO are used to constrain the total amount of emitted CO in the model and to identify the most appropriate vertical diffusion scheme. Zenith sky UV spectroscopy is used to estimate the emissions of SO2 from a large power plant and the Popocatépetl volcano. Results suggest that the models are able to identify correctly large point sources and that both the power plant and the volcano impact the MCMA. Modelled concentrations of CO based on the current emission inventory match observations suggesting that the current total emissions estimate is correct. Possible adjustments to the spatial and temporal distribution can be inferred from model results. Accurate source and dispersion modelling provides feedback for development of the emission inventory, verification of transport processes in air quality models and guidance for policy decisions.

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de Foy, B., W. Lei, M. Zavala, R. Volkamer, J. Samuelsson, J. Mellqvist, B. Galle et al. « Modelling constraints on the emission inventory and on vertical dispersion for CO and SO2 ; in the Mexico City Metropolitan Area using Solar FTIR and zenith sky UV spectroscopy ». Atmospheric Chemistry and Physics 7, n^o 3 (14 février 2007) : 781–801. http://dx.doi.org/10.5194/acp-7-781-2007.

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Abstract. Emissions of air pollutants in and around urban areas lead to negative health impacts on the population. To estimate these impacts, it is important to know the sources and transport mechanisms of the pollutants accurately. Mexico City has a large urban fleet in a topographically constrained basin leading to high levels of carbon monoxide (CO). Large point sources of sulfur dioxide (SO2) surrounding the basin lead to episodes with high concentrations. An Eulerian grid model (CAMx) and a particle trajectory model (FLEXPART) are used to evaluate the estimates of CO and SO2 in the current emission inventory using mesoscale meteorological simulations from MM5. Vertical column measurements of CO are used to constrain the total amount of emitted CO in the model and to identify the most appropriate vertical dispersion scheme. Zenith sky UV spectroscopy is used to estimate the emissions of SO2 from a large power plant and the Popocatépetl volcano. Results suggest that the models are able to identify correctly large point sources and that both the power plant and the volcano impact the MCMA. Modelled concentrations of CO based on the current emission inventory match observations suggesting that the current total emissions estimate is correct. Possible adjustments to the spatial and temporal distribution can be inferred from model results. Accurate source and dispersion modelling provides feedback for development of the emission inventory, verification of transport processes in air quality models and guidance for policy decisions.

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Donth, Tobias, Evelyn Jäkel, André Ehrlich, Bernd Heinold, Jacob Schacht, Andreas Herber, Marco Zanatta et Manfred Wendisch. « Combining atmospheric and snow radiative transfer models to assess the solar radiative effects of black carbon in the Arctic ». Atmospheric Chemistry and Physics 20, n^o 13 (13 juillet 2020) : 8139–56. http://dx.doi.org/10.5194/acp-20-8139-2020.

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Abstract. The magnitude of solar radiative effects (cooling or warming) of black carbon (BC) particles embedded in the Arctic atmosphere and surface snow layer was explored on the basis of case studies. For this purpose, combined atmospheric and snow radiative transfer simulations were performed for cloudless and cloudy conditions on the basis of BC mass concentrations measured in pristine early summer and more polluted early spring conditions. The area of interest is the remote sea-ice-covered Arctic Ocean in the vicinity of Spitsbergen, northern Greenland, and northern Alaska typically not affected by local pollution. To account for the radiative interactions between the black-carbon-containing snow surface layer and the atmosphere, an atmospheric and snow radiative transfer model were coupled iteratively. For pristine summer conditions (no atmospheric BC, minimum solar zenith angles of 55∘) and a representative BC particle mass concentration of 5 ng g−1 in the surface snow layer, a positive daily mean solar radiative forcing of +0.2 W m−2 was calculated for the surface radiative budget. A higher load of atmospheric BC representing early springtime conditions results in a slightly negative mean radiative forcing at the surface of about −0.05 W m−2, even when the low BC mass concentration measured in the pristine early summer conditions was embedded in the surface snow layer. The total net surface radiative forcing combining the effects of BC embedded in the atmosphere and in the snow layer strongly depends on the snow optical properties (snow specific surface area and snow density). For the conditions over the Arctic Ocean analyzed in the simulations, it was found that the atmospheric heating rate by water vapor or clouds is 1 to 2 orders of magnitude larger than that by atmospheric BC. Similarly, the daily mean total heating rate (6 K d−1) within a snowpack due to absorption by the ice was more than 1 order of magnitude larger than that of atmospheric BC (0.2 K d−1). Also, it was shown that the cooling by atmospheric BC of the near-surface air and the warming effect by BC embedded in snow are reduced in the presence of clouds.

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Wang, Junhong, et Liangying Zhang. « Systematic Errors in Global Radiosonde Precipitable Water Data from Comparisons with Ground-Based GPS Measurements ». Journal of Climate 21, n^o 10 (15 mai 2008) : 2218–38. http://dx.doi.org/10.1175/2007jcli1944.1.

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Abstract A global, 10-yr (February 1997–April 2006), 2-hourly dataset of atmospheric precipitable water (PW) was produced from ground-based global positioning system (GPS) measurements of zenith tropospheric delay (ZTD) at approximately 350 International Global Navigation Satellite Systems (GNSS) Service (IGS) ground stations. A total of 130 pairs of radiosonde and GPS stations are found within a 50-km distance and 100-m elevation of each other. At these stations, 14 types of radiosondes are launched and the following 3 types of humidity sensors are used: capacitive polymer, carbon hygristor, and goldbeater’s skin. The PW comparison between radiosonde and GPS data reveals three types of systematic errors in the global radiosonde PW data: measurement biases of the 14 radiosonde types along with their characteristics, long-term temporal inhomogeneity, and diurnal sampling errors of once- and twice-daily radiosonde data. The capacitive polymer generally shows mean dry bias of −1.19 mm (−6.8%). However, the carbon hygristor and goldbeater’s skin hygrometers have mean moist biases of 1.01 mm (3.4%) and 0.76 mm (5.4%), respectively. The protective shield over the humidity sensor boom introduced in late 2000 reduces the PW dry bias from 6.1% and 2.6% in 2000 to 3.9% and −1.14% (wet bias) in 2001 for the Vaisala RS80A and RS80H, respectively. The dry bias in Vaisala radiosondes has larger magnitudes during the day than at night, especially for RS90 and RS92, with a day–night difference of 5%–7%. The time series of monthly mean PW differences between the radiosonde and GPS are able to detect significant changes associated with known radiosonde type changes. Such changes would have a significant impact on the long-term trend estimate. Diurnal sampling errors of twice-daily radiosonde data are generally within 2%, but can be as much as 10%–15% for the once-daily soundings. In conclusion, this study demonstrates that the global GPS PW data are useful for identifying and quantifying several kinds of systematic errors in global radiosonde PW data. Several recommendations are made for future needs of global radiosonde and GPS networks and data.

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France, J. L., M. D. King, M. M. Frey, J. Erbland, G. Picard, S. Preunkert, A. MacArthur et J. Savarino. « Snow optical properties at Dome C (Concordia), Antarctica ; implications for snow emissions and snow chemistry of reactive nitrogen ». Atmospheric Chemistry and Physics 11, n^o 18 (21 septembre 2011) : 9787–801. http://dx.doi.org/10.5194/acp-11-9787-2011.

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Abstract. Measurements of e-folding depth, nadir reflectivity and stratigraphy of the snowpack around Concordia station (Dome C, 75.10° S, 123.31° E) were undertaken to determine wavelength dependent coefficients (350 nm to 550 nm) for light scattering and absorption and to calculate potential fluxes (depth-integrated production rates) of nitrogen dioxide (NO2) from the snowpack due to nitrate photolysis within the snowpack. The stratigraphy of the top 80 cm of Dome C snowpack generally consists of three main layers:- a surface of soft windpack (not ubiquitous), a hard windpack, and a hoar-like layer beneath the windpack(s). The e-folding depths are ~10 cm for the two windpack layers and ~20 cm for the hoar-like layer for solar radiation at a wavelength of 400 nm; about a factor 2–4 larger than previous model estimates for South Pole. The absorption cross-section due to impurities in each snowpack layer are consistent with a combination of absorption due to black carbon and HULIS (HUmic LIke Substances), with amounts of 1–2 ng g−1 of black carbon for the surface snow layers. Depth-integrated photochemical production rates of NO2 in the Dome C snowpack were calculated as 5.3 × 1012 molecules m−2 s−1, 2.3 × 1012 molecules m−2 s−1 and 8 × 1011 molecules m−2 s−1 for clear skies and solar zenith angles of 60°, 70° and 80° respectively using the TUV-snow radiative-transfer model. Depending upon the snowpack stratigraphy, a minimum of 85% of the NO2 may originate from the top 20 cm of the Dome C snowpack. It is found that on a multi-annual time-scale photolysis can remove up to 80% of nitrate from surface snow, confirming independent isotopic evidence that photolysis is an important driver of nitrate loss occurring in the EAIS (East Antarctic Ice Sheet) snowpack. However, the model cannot completely account for the total observed nitrate loss of 90–95 % or the shape of the observed nitrate concentration depth profile. A more complete model will need to include also physical processes such as evaporation, re-deposition or diffusion between the quasi-liquid layer on snow grains and firn air to account for the discrepancies.

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Newnham, David A., George P. Ford, Tracy Moffat-Griffin et Hugh C. Pumphrey. « Simulation study for measurement of horizontal wind profiles in the polar stratosphere and mesosphere using ground-based observations of ozone and carbon monoxide lines in the 230–250 GHz region ». Atmospheric Measurement Techniques 9, n^o 7 (26 juillet 2016) : 3309–23. http://dx.doi.org/10.5194/amt-9-3309-2016.

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Abstract. Meteorological and atmospheric models are being extended up to 80 km altitude but there are very few observing techniques that can measure stratospheric–mesospheric winds at altitudes between 20 and 80 km to verify model datasets. Here we demonstrate the feasibility of horizontal wind profile measurements using ground-based passive millimetre-wave spectroradiometric observations of ozone lines centred at 231.28, 249.79, and 249.96 GHz. Vertical profiles of horizontal winds are retrieved from forward and inverse modelling simulations of the line-of-sight Doppler-shifted atmospheric emission lines above Halley station (75°37′ S, 26°14′ W), Antarctica. For a radiometer with a system temperature of 1400 K and 30 kHz spectral resolution observing the ozone 231.28 GHz line we estimate that 12 h zonal and meridional wind profiles could be determined over the altitude range 25–74 km in winter, and 28–66 km in summer. Height-dependent measurement uncertainties are in the range 3–8 m s−1 and vertical resolution ∼ 8–16 km. Under optimum observing conditions at Halley a temporal resolution of 1.5 h for measuring either zonal or meridional winds is possible, reducing to 0.5 h for a radiometer with a 700 K system temperature. Combining observations of the 231.28 GHz ozone line and the 230.54 GHz carbon monoxide line gives additional altitude coverage at 85 ± 12 km. The effects of clear-sky seasonal mean winter/summer conditions, zenith angle of the received atmospheric emission, and spectrometer frequency resolution on the altitude coverage, measurement uncertainty, and height and time resolution of the retrieved wind profiles have been determined.

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Richardson, Mark, Jussi Leinonen, Heather Q. Cronk, James McDuffie, Matthew D. Lebsock et Graeme L. Stephens. « Marine liquid cloud geometric thickness retrieved from OCO-2's oxygen A-band spectrometer ». Atmospheric Measurement Techniques 12, n^o 3 (18 mars 2019) : 1717–37. http://dx.doi.org/10.5194/amt-12-1717-2019.

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Abstract. This paper introduces the OCO2CLD-LIDAR-AUX product, which uses the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar and the Orbiting Carbon Observatory-2 (OCO-2) hyperspectral A-band spectrometer. CALIPSO provides a prior cloud top pressure (Ptop) for an OCO-2-based retrieval of cloud optical depth, Ptop and cloud geometric thickness expressed in hPa. Measurements are of single-layer liquid clouds over oceans from September 2014 to December 2016 when collocated data are available. Retrieval performance is best for solar zenith angles <45∘ and when the cloud phase classification, which also uses OCO-2's weak CO2 band, is more confident. The highest quality optical depth retrievals agree with those from the Moderate Resolution Imaging Spectroradiometer (MODIS) with discrepancies smaller than the MODIS-reported uncertainty. Retrieved thicknesses are consistent with a substantially subadiabatic structure over marine stratocumulus regions, in which extinction is weighted towards the cloud top. Cloud top pressure in these clouds shows a 4 hPa bias compared with CALIPSO which we attribute mainly to the assumed vertical structure of cloud extinction after showing little sensitivity to the presence of CALIPSO-identified aerosol layers or assumed cloud droplet effective radius. This is the first case of success in obtaining internal cloud structure from hyperspectral A-band measurements and exploits otherwise unused OCO-2 data. This retrieval approach should provide additional constraints on satellite-based estimates of cloud droplet number concentration from visible imagery, which rely on parameterization of the cloud thickness.

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Li, G., N. Bei, X. Tie et L. T. Molina. « Aerosol effects on the photochemistry in Mexico City during MCMA-2006/MILAGRO campaign ». Atmospheric Chemistry and Physics Discussions 11, n^o 3 (14 mars 2011) : 8625–64. http://dx.doi.org/10.5194/acpd-11-8625-2011.

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Abstract. In the present study, the impact of aerosols on the photochemistry in Mexico City is evaluated using the WRF-CHEM model for the period from 24 to 29 March during the MCMA-2006/MILAGRO campaign. An aerosol radiative module has been developed with detailed consideration of aerosol size, composition, and mixture. The module has been coupled into the WRF-CHEM model to calculate the aerosol optical properties, including optical depth, single scattering albedo, and asymmetry factor. Calculated aerosol optical properties are in good agreement with the surface observations and aircraft and satellite measurements during daytime. In general, the photolysis rates are reduced due to the absorption by carbonaceous aerosols, particularly in the early morning and late afternoon with a long aerosol optical path. However, with the growth of aerosol particles and the decrease of the solar zenith angle around noontime, aerosols can slightly enhance photolysis rates when ultraviolet (UV) radiation scattering dominates UV absorption by aerosols. The changes in photolysis rates due to aerosols lead to about 2–17% surface ozone reduction during daytime in the urban area in Mexico City, resulting in a decrease of OH level by about 9%, as well as a decrease in the daytime concentrations of nitrate and secondary organic aerosols by 5–6% on average. In addition, the rapid aging of black carbon aerosols and the enhanced absorption of UV radiation by organic aerosols contribute substantially to the reduction of photolysis rates, resulting in a further decrease of other chemical species.

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Saito, Masanori, Ping Yang, Norman G. Loeb et Seiji Kato. « A Novel Parameterization of Snow Albedo Based on a Two-Layer Snow Model with a Mixture of Grain Habits ». Journal of the Atmospheric Sciences 76, n^o 5 (1 mai 2019) : 1419–36. http://dx.doi.org/10.1175/jas-d-18-0308.1.

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Abstract Snow albedo plays a critical role in the surface energy budget in snow-covered regions and is subject to large uncertainty due to variable physical and optical characteristics of snow. We develop an optically and microphysically consistent snow grain habit mixture (SGHM) model, aiming at an improved representation of bulk snow properties in conjunction with considering the particle size distribution, particle shape, and internally mixed black carbon (BC). Spectral snow albedos computed with two snow layers with the SGHM model implemented in an adding–doubling radiative transfer model agree with observations. Top-snow-layer optical properties essentially determine spectral snow albedo when the top-layer snow water equivalent (SWE) is large. When the top-layer SWE is less than 1 mm, the second-snow-layer optical properties have nonnegligible impacts on the albedo of the snow surface. Snow albedo enhancement with increasing solar zenith angle (SZA) largely depends on snow particle effective radius and also internally mixed BC. Based on the SGHM model and various sensitivity studies, single- and two-layer snow albedos are parameterized for six spectral bands used in NASA Langley Research Center’s modified Fu–Liou broadband radiative transfer model. Parameterized albedo is expressed as a function of snow particle effective radii of the two layers, SWE in the top layer, internally mixed BC mass fraction in both layers, and SZA. Both single-layer and two-layer parameterizations provide band-mean snow albedo consistent with rigorous calculations, achieving correlation coefficients close to 0.99 for all bands.

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Yuan, Hua, Robert E. Dickinson, Yongjiu Dai, Muhammad J. Shaikh, Liming Zhou, Wei Shangguan et Duoying Ji. « A 3D Canopy Radiative Transfer Model for Global Climate Modeling : Description, Validation, and Application ». Journal of Climate 27, n^o 3 (24 janvier 2014) : 1168–92. http://dx.doi.org/10.1175/jcli-d-13-00155.1.

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Abstract The process of solar radiative transfer at the land surface is important to energy, water, and carbon balance, especially for vegetated areas. Currently the most commonly used two-stream model considers the plant functional types (PFTs) within a grid to be independent of each other and their leaves to be horizontally homogeneous. This assumption is unrealistic in most cases. To consider canopy three-dimensional (3D) structural effects, a new framework of 3D canopy radiative transfer model was developed and validated by numerical simulations and shows a good agreement. A comparison with the two-stream model in the offline Community Land Model (CLM4.0) shows that an increase of canopy absorption mainly happens with sparse vegetation or with multilayer canopies with a large sun zenith angle θsun and is due to increases of the ground and sky shadows and of the optical pathlength because of the shadow overlapping between bushes and canopy layers. A decrease of canopy absorption occurs in densely vegetated areas with small θsun. For a one-layer canopy, these decreases are due to crown shape effects that enhance the transmission through the canopy edge. For a multilayer canopy, aside from these shape effects, transmission is also increased by the decreased ground shadow due to the shadow overlapping between layers. Ground absorption usually changes with opposite sign as that of the canopy absorption. Somewhat lower albedos are found over most vegetated areas throughout the year. The 3D model also affects the calculation of the fraction of sunlit leaves and their corresponding absorption.

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Li, G., N. Bei, X. Tie et L. T. Molina. « Aerosol effects on the photochemistry in Mexico City during MCMA-2006/MILAGRO campaign ». Atmospheric Chemistry and Physics 11, n^o 11 (1 juin 2011) : 5169–82. http://dx.doi.org/10.5194/acp-11-5169-2011.

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Abstract. In the present study, the impact of aerosols on the photochemistry in Mexico City is evaluated using the WRF-CHEM model for the period from 24 to 29 March during the MCMA-2006/MILAGRO campaign. An aerosol radiative module has been developed with detailed consideration of aerosol size, composition, and mixing. The module has been coupled into the WRF-CHEM model to calculate the aerosol optical properties, including optical depth, single scattering albedo, and asymmetry factor. Calculated aerosol optical properties are in good agreement with the surface observations and aircraft and satellite measurements during daytime. In general, the photolysis rates are reduced due to the absorption by carbonaceous aerosols, particularly in the early morning and late afternoon hours with a long aerosol optical path. However, with the growth of aerosol particles and the decrease of the solar zenith angle around noontime, aerosols can slightly enhance photolysis rates when ultraviolet (UV) radiation scattering dominates UV absorption by aerosols at the lower-most model layer. The changes in photolysis rates due to aerosols lead to about 2–17 % surface ozone reduction during daytime in the urban area in Mexico City with generally larger reductions during early morning hours near the city center, resulting in a decrease of OH level by about 9 %, as well as a decrease in the daytime concentrations of nitrate and secondary organic aerosols by 5–6 % on average. In addition, the rapid aging of black carbon aerosols and the enhanced absorption of UV radiation by organic aerosols contribute substantially to the reduction of photolysis rates.

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Bertaux, Jean-Loup, Alain Hauchecorne, Franck Lefèvre, François-Marie Bréon, Laurent Blanot, Denis Jouglet, Pierre Lafrique et Pavel Akaev. « The use of the 1.27 µm O2 ; absorption band for greenhouse gas monitoring from space and application to MicroCarb ». Atmospheric Measurement Techniques 13, n^o 6 (24 juin 2020) : 3329–74. http://dx.doi.org/10.5194/amt-13-3329-2020.

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Abstract. Monitoring CO2 from space is essential to characterize the spatiotemporal distribution of this major greenhouse gas and quantify its sources and sinks. The mixing ratio of CO2 to dry air can be derived from the CO2∕O2 column ratio. The O2 column is usually derived from its absorption signature on the solar reflected spectra over the O2 A band (e.g. Orbiting Carbon Observatory-2 (OCO-2), Thermal And Near infrared Sensor for carbon Observation (TANSO)/Greenhouse Gases Observing Satellite (GOSAT), TanSat). As a result of atmospheric scattering, the atmospheric path length varies with the aerosols' load, their vertical distribution, and their optical properties. The spectral distance between the O2 A band (0.76 µm) and the CO2 absorption band (1.6 µm) results in significant uncertainties due to the varying spectral properties of the aerosols over the globe. There is another O2 absorption band at 1.27 µm with weaker lines than in the A band. As the wavelength is much closer to the CO2 and CH4 bands, there is less uncertainty when using it as a proxy of the atmospheric path length to the CO2 and CH4 bands. This O2 band is used by the Total Carbon Column Observing Network (TCCON) implemented for the validation of space-based greenhouse gas (GHG) observations. However, this absorption band is contaminated by the spontaneous emission of the excited molecule O2*, which is produced by the photo-dissociation of O3 molecules in the stratosphere and mesosphere. From a satellite looking nadir, this emission has a similar shape to the absorption signal that is used. In the frame of the CNES (Centre National d'Études Spatiales – the French National Centre for Space Studies) MicroCarb project, scientific studies have been performed in 2016–2018 to explore the problems associated with this O2* airglow contamination and methods to correct it. A theoretical synthetic spectrum of the emission was derived from an approach based on A21 Einstein coefficient information contained in the line-by-line high-resolution transmission molecular absorption (HITRAN) 2016 database. The shape of our synthetic spectrum is validated when compared to O2* airglow spectra observed by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY)/Envisat in limb viewing. We have designed an inversion scheme of SCIAMACHY limb-viewing spectra, allowing to determine the vertical distribution of the volume emission rate (VER) of the O2* airglow. The VER profiles and corresponding integrated nadir intensities were both compared to a model of the emission based on the Reactive Processes Ruling the Ozone Budget in the Stratosphere (REPROBUS) chemical transport model. The airglow intensities depend mostly on the solar zenith angle (both in model and data), and the model underestimates the observed emission by ∼15 %. This is confirmed with SCIAMACHY nadir-viewing measurements over the oceans: in such conditions, we have disentangled and retrieved the nadir O2* emission in spite of the moderate spectral resolving power (∼860) and found that the nadir SCIAMACHY intensities are mostly dictated by solar zenith angle (SZA) and are larger than the model intensities by a factor of ∼1.13. At a fixed SZA, the model airglow intensities show very little horizontal structure, in spite of ozone variations. It is shown that with the MicroCarb spectral resolution power (25 000) and signal-to-noise ratio (SNR), the contribution of the O2* emission at 1.27 µm to the observed spectral radiance in nadir viewing may be disentangled from the lower atmosphere/ground absorption signature with a great accuracy. Indeed, simulations with 4ARCTIC radiative transfer inversion tool have shown that the CO2 mixing ratio may be retrieved with the accuracy required for quantifying the CO2 natural sources and sinks (pressure-level error ≤1 hPa; XCO2 accuracy better than 0.4 ppmv) with the O2 1.27 µm band only as the air proxy (without the A band). As a result of these studies (at an intermediate phase), it was decided to include this band (B4) in the MicroCarb design, while keeping the O2 A band for reference (B1). Our approach is consistent with the approach of Sun et al. (2018), who also analysed the potential of the O2 1.27 µm band and concluded favourably for GHG monitoring from space. We advocate for the inclusion of this O2 band on other GHG monitoring future space missions, such as GOSAT-3 and EU/European Space Agency (ESA) CO2-M missions, for a better GHG retrieval.

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Rusli, Stephanie P., Otto Hasekamp, Joost aan de Brugh, Guangliang Fu, Yasjka Meijer et Jochen Landgraf. « Anthropogenic CO2 ; monitoring satellite mission : the need for multi-angle polarimetric observations ». Atmospheric Measurement Techniques 14, n^o 2 (15 février 2021) : 1167–90. http://dx.doi.org/10.5194/amt-14-1167-2021.

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Abstract. Atmospheric aerosols have been known to be a major source of uncertainties in CO2 concentrations retrieved from space. In this study, we investigate the added value of multi-angle polarimeter (MAP) measurements in the context of the Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) mission. To this end, we compare aerosol-induced XCO2 errors from standard retrievals using a spectrometer only (without MAP) with those from retrievals using both MAP and a spectrometer. MAP observations are expected to provide information about aerosols that is useful for improving XCO2 accuracy. For the purpose of this work, we generate synthetic measurements for different atmospheric and geophysical scenes over land, based on which XCO2 retrieval errors are assessed. We show that the standard XCO2 retrieval approach that makes no use of auxiliary aerosol observations returns XCO2 errors with an overall bias of 1.12 ppm and a spread (defined as half of the 15.9–84.1 percentile range) of 2.07 ppm. The latter is far higher than the required XCO2 accuracy (0.5 ppm) and precision (0.7 ppm) of the CO2M mission. Moreover, these XCO2 errors exhibit a significantly larger bias and scatter at high aerosol optical depth, high aerosol altitude, and low solar zenith angle, which could lead to worse performance in retrieving XCO2 from polluted areas where CO2 and aerosols are co-emitted. We proceed to determine MAP instrument specifications in terms of wavelength range, number of viewing angles, and measurement uncertainties that are required to achieve XCO2 accuracy and precision targets of the mission. Two different MAP instrument concepts are considered in this analysis. We find that for either concept, MAP measurement uncertainties on radiance and degree of linear polarization should be no more than 3 % and 0.003, respectively. A retrieval exercise using MAP and spectrometer measurements of the synthetic scenes is carried out for each of the two MAP concepts. The resulting XCO2 errors have an overall bias of −0.004 ppm and a spread of 0.54 ppm for one concept, and a bias of 0.02 ppm and a spread of 0.52 ppm for the other concept. Both are compliant with the CO2M mission requirements; the very low bias is especially important for proper emission estimates. For the test ensemble, we find effectively no dependence of the XCO2 errors on aerosol optical depth, altitude of the aerosol layer, and solar zenith angle. These results indicate a major improvement in the retrieved XCO2 accuracy with respect to the standard retrieval approach, which could lead to a higher data yield, better global coverage, and a more comprehensive determination of CO2 sinks and sources. As such, this outcome underlines the contribution of, and therefore the need for, a MAP instrument aboard the CO2M mission.

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Kreuter, M., F. Bonella, K. Kathrin, J. Henes, E. Siegert, G. Riemekasten, N. Blank et al. « POS0834 LONG-TERM OUTCOME OF SSC ASSOCIATED ILD : IMPROVED SURVIVAL IN PPI TREATED PATIENTS ». Annals of the Rheumatic Diseases 80, Suppl 1 (19 mai 2021) : 670.2–671. http://dx.doi.org/10.1136/annrheumdis-2021-eular.878.

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Background:Gastroesophageal reflux disease (GERD) occurs frequently in patients with systemic sclerosis (SSc) and SSc-associated interstitial lung disease (SSc-ILD). PPI use has to been shown to improve survival in patients with idiopathic pulmonary fibrosis, whereas to date there are no data on the use of PPI in SSc-ILD.Objectives:This study was aimed to assess whether use of PPI is associated with progression of SSc-ILD and survival.Methods:We retrospectively analysed 1931 patients with SSc and SSc-ILD from the German Network for Systemic Sclerosis (DNSS) database (2003 onwards). Kaplan–Meier analysis compared overall survival (OS) and progression-free survival (PFS) in patients with vs. without GERD (SSc and SSc-ILD), and PPI vs. no PPI use (SSc-ILD only). Progression was defined as a decrease in either % predicted forced vital capacity ≥10% or single-breath diffusing capacity for carbon monoxide ≥15%, or death.Results:GERD was not associated with decreased OS or PFS in patients with either SSc or SSc-ILD. In patients with SSc-ILD, PPI use was associated with improved OS vs. no PPI use after 1 year (98.4% [95% confidence interval: 97.6–99.3]; n=760 vs. 90.8% [87.9–93.8]; n=290) and after 5 years (91.4% [89.2–93.8]; n=357 vs. 70.9% [65.2–77.1]; n=106; p<0.0001). PPI use was also associated with improved PFS vs. no PPI use after 1 year (95.9% [94.6–97.3]; n=745 vs. 86.4% [82.9–90.1]; n=278) and after 5 years (66.8% [63.0–70.8]; n=286 vs. 45.9% [39.6–53.2]; n=69; p<0.0001).Conclusion:GERD had no effect on survival in SSc or SSc-ILD. PPIs improved survival in patients with SSc-ILD; however, controlled, prospective trials are needed to confirm this finding.Disclosure of Interests:Michael Kreuter Speakers bureau: Boehringer, Consultant of: Boehringer, Grant/research support from: Boehringer, Francesco Bonella Speakers bureau: Boehringer, Roche, GSK, Consultant of: Boehringer, Roche, GSK, Grant/research support from: Boehringer, Kuhr Kathrin: None declared, Jörg Henes Speakers bureau: Abbvie, Boehringer, Chugai, Roche, Janssen, Novartis, SOBI, Pfizer and UCB, Consultant of: Boehringer, Celgene, Chugai, Roche, Janssen, Novartis, SOBI, Grant/research support from: Chugai, Roche, Janssen, Novartis, SOBI, Pfizer, Elise Siegert: None declared, Gabriela Riemekasten Speakers bureau: Novartis, Janssen, Roche, GSK, Boehringer, Consultant of: Janssen, Actelion, Boehringer, Norbert Blank Consultant of: Sobi, Novartis, Roche, UCB, MSD, Pfizer, Actelion, Abbvie, Boehringer, Grant/research support from: Novartis, Sobi, Christiane Pfeiffer: None declared, Ulf Müller-Ladner: None declared, Alexander Kreuter Speakers bureau: MSD, Boehringer, InfectoPharm, Paid instructor for: MSD, PETER KORSTEN Consultant of: Glaxo, Abbvie, Pfizer, BMS, Chugai, Sanofi, Lilly, Boehringer, Novartis, Grant/research support from: Glaxo, Aaron Juche: None declared, Marc Schmalzing Speakers bureau: Chugai Roche, Boehringer, Celgene, Medac, UCB, Paid instructor for: Novartis, Abbvie, Astra Zeneca, Chugai Roche, Janssen, Consultant of: Chugai Roche, Hexal Sandoz, Gilead, Abbvie, Janssen, Boehringer, Margitta Worm Speakers bureau: Boehringer, Ilona Jandova Speakers bureau: Boehringer, Novartis, Abbvie, Laura Susok Speakers bureau: MSD, Novartis, BMS, Sunpharma, Consultant of: MSD, Tim Schmeiser Consultant of: Abbvie, Boehringer, Novartis, UCB, Claudia Guenther Paid instructor for: Advisory Board Boehringer January 2020, Employee of: Novartis 2002-2005, Gernot Keyszer Consultant of: Boehringer, Jan Ehrchen Speakers bureau: Boehringer, Janssen, Chugai, Sobi, Employee of: Pfizer, Actelion (now Janssen), Andreas Ramming Speakers bureau: Boehringer, Gilead, Janssen, Pfizer, Roche, Consultant of: Boehringer, Pfizer, Grant/research support from: Novartis, Pfizer, Ina Kötter Speakers bureau: several companies, Consultant of: several companies, Grant/research support from: several companies, Hanns-Martin Lorenz Speakers bureau: Abbvie, Astra Zeneca, Actelion, Alexion Amgen, Bayer Vital, Baxter, Biogen, Boehringer, BMS, Celgene, Fresenius, Genzyme, GSK, Gilead, Hexal, Janssen, Lilly, Medac, MSD, Mundipharm, Mylan, Novartis, Octapharm, Pfizer, Roche Chugai, Sandoz, Sanofi, Shire SOBI, Thermo Fischer, UCB, Grant/research support from: basic research studies: Pfizer, Novartis, Abbvie, Gilead, Lilly, MSD, Roche Chugai, Pia Moinzadeh Speakers bureau: Boehringer, Actelion, Grant/research support from: Actelion, Nicolas Hunzelmann Speakers bureau: Boehringer Janssen, Roche, Sanofi, Consultant of: Boehringer

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Schilirò, D., E. Elefante, C. Stagnaro, V. Signorini, D. Zucchi, F. Trentin, G. La Rocca et al. « AB0555 SYMPTOMATIC NON-SEROSITIC LUNG INVOLVEMENT IN A MONOCENTRIC COHORT OF PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) : A REAL-LIFE EXPERIENCE ». Annals of the Rheumatic Diseases 81, Suppl 1 (23 mai 2022) : 1404.2–1405. http://dx.doi.org/10.1136/annrheumdis-2022-eular.4606.

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BackgroundA growing interest has been addressed to the study of lung involvement in systemic autoimmune diseases. Non-serositic pulmonary manifestations have also been described in SLE. However, little is known about their exact prevalence, clinical features and outcomes.ObjectivesTo describe the prevalence, clinical and immunological characteristics of symptomatic non-serositic lung involvement in a monocentric cohort of SLE patients.MethodsThis observational, retrospective study included patients with SLE, regularly followed at the Rheumatology Unit of Pisa, that presented a clinically relevant non-serositic pulmonary involvement during their disease history. Patients with lung manifestations related to other causes (e.g. infections, emphysema, Chronic Obstructive Lung Disease, bronchial asthma etc.) were excluded. The following data were collected from clinical charts: demographics, smoke exposure, comorbidities, respiratory symptoms, disease duration and disease activity (SELENA-SLEDAI) at the onset of lung involvement, immunological profile, treatment, CT and spirometry parameters.ResultsOver 450 SLE patients in regular follow-up, we found 11 female patients with a history of clinically relevant non-serositic lung involvement: 7 interstitial lung disease (ILD), 2 acute lupic pneumonitis (ALP), 1 diffuse alveolar hemorrhage (DAH) and 1 shrinking lung syndrome. 45.4% of patients had a history of smoke exposure and had stopped smoking on average 9 years before the onset of lung manifestations. For the 2 patients with ALP, this was the first manifestation of SLE. Among the other 9 patients, lung involvement was diagnosed after a mean disease duration of 14 ± 15 years. At the diagnosis of pulmonary involvement, 10/11 patients presented respiratory symptoms and an overall active disease, with a median SLEDAI of 9 (IQR 6-13). Clinical characteristics are summarized in Table 1. All patients were hospitalized and 2 of them (1 ALP and 1 DAH) were admitted in intensive care unit.Table 1.Clinical characteristics at the diagnosis of lung involvementSystemicActive skin manifestations36%Arthritis36%Fever36%Leukopenia36%Hypocomplementemia91%Anti-dsDNA positivity36%RespiratoryDyspnea54%Exertional dyspnea18%Cough45%Acute respiratory failure27%As for the immunologic profile, SSA/Ro60 were positive in 72% of patients and SSA/Ro52, SSB, U1-RNP in 36%; 36% had Sjogren Syndrome (SS) in overlap.Spirometry was available for 6/11 patients: a restrictive pattern and a moderate/severe reduction of diffusing capacity of the lung for carbon monoxide was found in 5 patients.In the ILD subgroup, the most prevalent CT pattern was the Non-specific interstitial pneumonia (NSIP) (5/7). 2 patients presented a Bronchiolitis obliterans/organizing pneumonia (BOOP) pattern.Lung involvement was the driving manifestation in the treatment choice for 6/11 patients: 1 DAH, 2 ALP, 1 Shrinking lung and 2 ILD. All received pulse steroids and in 3 cases (2 ILD and 1 DAH) cyclophosphamide was added for the induction treatment; the patient with Shrinking lung had an overlap SS and was treated with Rituximab.At last visit (mean follow-up of 8 ± 8.7 years since lung disease onset), 7/11 patients presented no respiratory symptoms and a complete resolution of CT alterations. 3/11 presented a residual exertional dyspnea and mild spirometry alterations. No patients developed respiratory insufficiency; only 1 patient died for cardiovascular complications.ConclusionIn our large cohort of SLE patients, non-serositic lung involvement seems to be overall rare; the most frequent type of lung manifestation is ILD which appears to be associated with anti-SSA/SSB and anti-U1RNP positivity. The low prevalence of lung involvement (2.4%) in our cohort could be due to the presence of patients with a subclinical involvement. Further studies are needed to assess the real prevalence of subclinical lung manifestations in SLE and to identify the clinical phenotype of patients more prone to develop pulmonary disease.Disclosure of InterestsDavide Schilirò: None declared, Elena Elefante: None declared, Chiara Stagnaro: None declared, Viola Signorini: None declared, Dina Zucchi: None declared, Francesca Trentin: None declared, Gaetano La Rocca: None declared, Linda Carli: None declared, Francesco Ferro: None declared, Chiara Tani: None declared, Marta Mosca Speakers bureau: advisor LILLY, ASTRA ZENECA, GSK, Consultant of: advisor LILLY, ASTRA ZENECA, GSK

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Brede, B., J. Verbesselt, L. Dutrieux et M. Herold. « Performance of the Enhanced Vegetation Index to Detect Inner-annual Dry Season and Drought Impacts on Amazon Forest Canopies ». ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-7/W3 (29 avril 2015) : 337–44. http://dx.doi.org/10.5194/isprsarchives-xl-7-w3-337-2015.

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The Amazon rainforests represent the largest connected forested area in the tropics and play an integral role in the global carbon cycle. In the last years the discussion about their phenology and response to drought has intensified. A recent study argued that seasonality in greenness expressed as Enhanced Vegetation Index (EVI) is an artifact of variations in sun-sensor geometry throughout the year. We aimed to reproduce these results with the Moderate-Resolution Imaging Spectroradiometer (MODIS) MCD43 product suite, which allows modeling the Bidirectional Reflectance Distribution Function (BRDF) and keeping sun-sensor geometry constant. The derived BRDF-adjusted EVI was spatially aggregated over large areas of central Amazon forests. The resulting time series of EVI spanning the 2000-2013 period contained distinct seasonal patterns with peak values at the onset of the dry season, but also followed the same pattern of sun geometry expressed as Solar Zenith Angle (SZA). Additionally, we assessed EVI’s sensitivity to precipitation anomalies. For that we compared BRDF-adjusted EVI dry season anomalies to two drought indices (Maximum Cumulative Water Deficit, Standardized Precipitation Index). This analysis covered the whole of Amazonia and data from the years 2000 to 2013. The results showed no meaningful connection between EVI anomalies and drought. This is in contrast to other studies that investigate the drought impact on EVI and forest photosynthetic capacity. The results from both sub-analyses question the predictive power of EVI for large scale assessments of forest ecosystem functioning in Amazonia. Based on the presented results, we recommend a careful evaluation of the EVI for applications in tropical forests, including rigorous validation supported by ground plots.

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Wei, Xiaoxu, Xufeng Wang, Wei Wei et Wei Wan. « Use of Sun-Induced Chlorophyll Fluorescence Obtained by OCO-2 and GOME-2 for GPP Estimates of the Heihe River Basin, China ». Remote Sensing 10, n^o 12 (14 décembre 2018) : 2039. http://dx.doi.org/10.3390/rs10122039.

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Sun-induced chlorophyll fluorescence (SIF) provides a new method for monitoring vegetation photosynthesis from space and has been widely used to estimate gross primary productivity (GPP). However, the ability of SIF obtained from the Orbital Carbon Observatory 2 (OCO-2 SIF) and Global Ozone Monitoring Experiment-2 (GOME-2) to estimate GPP in the cold and arid region of Heihe River Basin remains unclear because previous comparisons were insufficient. Here, we choose maize and alpine meadow to evaluate the performance of SIF obtained by OCO-2 and GOME-2 in GPP estimations. The results of this study show that daily SIF757 had stronger correlations with daily tower GPP than daily SIF771, and the correlation between daily SIF757 and daily tower GPP was stronger than the correlation between 16-d averaged SIF740 and 16-d averaged tower GPP. The 16-d averaged absorbed photosynthetically active radiation (APAR) and reconstructed sun-induced fluorescence (RSIF) had the strongest linear correlations with 16-d averaged tower GPP. GPP_VPM and GPP_RSIF exhibited the best performance in GPP estimation, closely followed by GPP_SIF757, then GPP_SIF771 and GPP_ SIF740. We also found that the robustness of the correlation coefficients of OCO-2 SIF with GOME-2 SIF was highly dependent on the size of their spatial footprint overlaps, indicating that the spatial differences between OCO-2 and GOME-2 footprints contribute to the differences in GPP estimates between OCO-2 and GOME-2. In addition, the differences of viewing zenith angle (VZA), cloud contamination, scale effects, and environmental scalars (Tscalar × Wscalar) can result in differences between OCO-2 SIF and GOME-2 SIF.

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Taylor, Thomas E., Christopher W. O'Dell, Christian Frankenberg, Philip T. Partain, Heather Q. Cronk, Andrey Savtchenko, Robert R. Nelson et al. « Orbiting Carbon Observatory-2 (OCO-2) cloud screening algorithms : validation against collocated MODIS and CALIOP data ». Atmospheric Measurement Techniques 9, n^o 3 (8 mars 2016) : 973–89. http://dx.doi.org/10.5194/amt-9-973-2016.

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Abstract. The objective of the National Aeronautics and Space Administration's (NASA) Orbiting Carbon Observatory-2 (OCO-2) mission is to retrieve the column-averaged carbon dioxide (CO2) dry air mole fraction (XCO2) from satellite measurements of reflected sunlight in the near-infrared. These estimates can be biased by clouds and aerosols, i.e., contamination, within the instrument's field of view. Screening of the most contaminated soundings minimizes unnecessary calls to the computationally expensive Level 2 (L2) XCO2 retrieval algorithm. Hence, robust cloud screening methods have been an important focus of the OCO-2 algorithm development team. Two distinct, computationally inexpensive cloud screening algorithms have been developed for this application. The A-Band Preprocessor (ABP) retrieves the surface pressure using measurements in the 0.76 µm O2 A band, neglecting scattering by clouds and aerosols, which introduce photon path-length differences that can cause large deviations between the expected and retrieved surface pressure. The Iterative Maximum A Posteriori (IMAP) Differential Optical Absorption Spectroscopy (DOAS) Preprocessor (IDP) retrieves independent estimates of the CO2 and H2O column abundances using observations taken at 1.61 µm (weak CO2 band) and 2.06 µm (strong CO2 band), while neglecting atmospheric scattering. The CO2 and H2O column abundances retrieved in these two spectral regions differ significantly in the presence of cloud and scattering aerosols. The combination of these two algorithms, which are sensitive to different features in the spectra, provides the basis for cloud screening of the OCO-2 data set.To validate the OCO-2 cloud screening approach, collocated measurements from NASA's Moderate Resolution Imaging Spectrometer (MODIS), aboard the Aqua platform, were compared to results from the two OCO-2 cloud screening algorithms. With tuning of algorithmic threshold parameters that allows for processing of ≃ 20–25 % of all OCO-2 soundings, agreement between the OCO-2 and MODIS cloud screening methods is found to be ≃ 85 % over four 16-day orbit repeat cycles in both the winter (December) and spring (April–May) for OCO-2 nadir-land, glint-land and glint-water observations.No major, systematic, spatial or temporal dependencies were found, although slight differences in the seasonal data sets do exist and validation is more problematic with increasing solar zenith angle and when surfaces are covered in snow and ice and have complex topography. To further analyze the performance of the cloud screening algorithms, an initial comparison of OCO-2 observations was made to collocated measurements from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). These comparisons highlight the strength of the OCO-2 cloud screening algorithms in identifying high, thin clouds but suggest some difficulty in identifying some clouds near the surface, even when the optical thicknesses are greater than 1.

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Taylor, T. E., C. W. O'Dell, C. Frankenberg, P. Partain, H. Q. Cronk, A. Savtchenko, R. R. Nelson et al. « Orbiting Carbon Observatory-2 (OCO-2) cloud screening algorithms ; validation against collocated MODIS and CALIOP data ». Atmospheric Measurement Techniques Discussions 8, n^o 12 (4 décembre 2015) : 12663–707. http://dx.doi.org/10.5194/amtd-8-12663-2015.

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Abstract. The objective of the National Aeronautics and Space Administration's (NASA) Orbiting Carbon Observatory-2 (OCO-2) mission is to retrieve the column-averaged carbon dioxide (CO2) dry air mole fraction (XCO2) from satellite measurements of reflected sunlight in the near-infrared. These estimates can be biased by clouds and aerosols within the instrument's field of view (FOV). Screening of the most contaminated soundings minimizes unnecessary calls to the computationally expensive Level 2 (L2) XCO2 retrieval algorithm. Hence, robust cloud screening methods have been an important focus of the OCO-2 algorithm development team. Two distinct, computationally inexpensive cloud screening algorithms have been developed for this application. The A-Band Preprocessor (ABP) retrieves the surface pressure using measurements in the 0.76 μm O2 A-band, neglecting scattering by clouds and aerosols, which introduce photon path-length (PPL) differences that can cause large deviations between the expected and retrieved surface pressure. The Iterative Maximum A-Posteriori (IMAP) Differential Optical Absorption Spectroscopy (DOAS) Preprocessor (IDP) retrieves independent estimates of the CO2 and H2O column abundances using observations taken at 1.61 μm (weak CO2 band) and 2.06 μm (strong CO2 band), while neglecting atmospheric scattering. The CO2 and H2O column abundances retrieved in these two spectral regions differ significantly in the presence of cloud and scattering aerosols. The combination of these two algorithms, which key off of different features in the spectra, provides the basis for cloud screening of the OCO-2 data set. To validate the OCO-2 cloud screening approach, collocated measurements from NASA's Moderate Resolution Imaging Spectrometer (MODIS), aboard the Aqua platform, were compared to results from the two OCO-2 cloud screening algorithms. With tuning to allow throughputs of &simeq; 30 %, agreement between the OCO-2 and MODIS cloud screening methods is found to be &simeq; 85 % over four 16-day orbit repeat cycles in both the winter (December) and spring (April–May) for OCO-2 nadir-land, glint-land and glint-water observations. No major, systematic, spatial or temporal dependencies were found, although slight differences in the seasonal data sets do exist and validation is more problematic with increasing solar zenith angle and when surfaces are covered in snow and ice and have complex topography. To further analyze the performance of the cloud screening algorithms, an initial comparison of OCO-2 observations was made to collocated measurements from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). These comparisons highlight the strength of the OCO-2 cloud screening algorithms in identifying high, thin clouds but suggest some difficulty in identifying some clouds near the surface, even when the optical thicknesses are greater than 1.

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