Literatura académica sobre el tema "Stratospheric ice clouds"
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Artículos de revistas sobre el tema "Stratospheric ice clouds"
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Zou, Ling, Sabine Griessbach, Lars Hoffmann y Reinhold Spang. "A global view on stratospheric ice clouds: assessment of processes related to their occurrence based on satellite observations". Atmospheric Chemistry and Physics 22, n.º 10 (23 de mayo de 2022): 6677–702. http://dx.doi.org/10.5194/acp-22-6677-2022.
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Abstract. Ice clouds play an important role in regulating water vapor and influencing the radiative budget in the atmosphere. This study investigates stratospheric ice clouds (SICs) in the latitude range between ±60∘ based on the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). As polar stratospheric clouds include other particles, they are not discussed in this work. Tropopause temperature, double tropopauses, clouds in the upper troposphere and lower stratosphere (UTLS), gravity waves, and stratospheric aerosols are analyzed to investigate their relationships with the occurrence of and variability in SICs in the tropics and at midlatitudes. We found that SICs with cloud-top heights of 250 m above the first lapse rate tropopause are mainly detected in the tropics. Monthly time series of SICs from 2007 to 2019 show that high occurrence frequencies of SICs follow the Intertropical Convergence Zone (ITCZ) over time in the tropics and that SICs vary interannually at different latitudes. Results show that SICs associated with double tropopauses, which are related to poleward isentropic transport, are mostly found at midlatitudes. More than 80 % of the SICs around 30∘ N/S are associated with double tropopauses. Correlation coefficients of SICs and all the other abovementioned processes confirm that the occurrence of and variability in SICs are mainly associated with the tropopause temperature in the tropics and at midlatitudes. UTLS clouds, which are retrieved from the Atmospheric Infrared Sounder (AIRS) and used as a proxy for deep convection in the tropics and high-altitude ice cloud sources at midlatitudes, have the highest correlations with SICs in the monsoon regions and the central United States. Gravity waves are mostly related to SICs at midlatitudes, especially over Patagonia and the Drake Passage. However, the second-highest correlation coefficients show that the cold tropopause temperature, the occurrence of double tropopauses, high stratospheric aerosol loading, frequent UTLS clouds, and gravity waves are highly correlated with the SICs locally. The long-term anomaly analyses show that interannual anomalies of SICs are correlated with the tropopause temperature and stratospheric aerosols instead of the UTLS clouds and gravity waves. The overlapping and similar correlation coefficients between SICs and all processes mentioned above indicate strong associations between those processes themselves. Due to their high inherent correlations, it is challenging to disentangle and evaluate their contributions to the occurrence of SICs on a global scale. However, the correlation coefficient analyses between SICs and all abovementioned processes (tropopause temperature, double tropopauses, clouds in the upper troposphere and lower stratosphere (UTLS), gravity waves, and stratospheric aerosols) in this study help us better understand the sources of SICs on a global scale.
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de Reus, M., S. Borrmann, A. Bansemer, A. J. Heymsfield, R. Weigel, C. Schiller, V. Mitev et al. "Evidence for ice particles in the tropical stratosphere from in-situ measurements". Atmospheric Chemistry and Physics 9, n.º 18 (18 de septiembre de 2009): 6775–92. http://dx.doi.org/10.5194/acp-9-6775-2009.
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Abstract. In-situ ice crystal size distribution measurements are presented within the tropical troposphere and lower stratosphere. The measurements were performed using a combination of a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP), which were installed on the Russian high altitude research aircraft M55 "Geophysica" during the SCOUT-O3 campaign in Darwin, Australia. One of the objectives of the campaign was to characterise the Hector convective system, which appears on an almost daily basis during the pre-monsoon season over the Tiwi Islands, north of Darwin. In total 90 encounters with ice clouds, between 10 and 19 km altitude were selected from the dataset and were analysed. Six of these encounters were observed in the lower stratosphere, up to 1.4 km above the local tropopause. Concurrent lidar measurements on board "Geophysica" indicate that these ice clouds were a result of overshooting convection. Large ice crystals, with a maximum dimension up to 400 μm, were observed in the stratosphere. The stratospheric ice clouds included an ice water content ranging from 7.7×10−5 to 8.5×10−4 g m−3 and were observed at ambient relative humidities (with respect to ice) between 75 and 157%. Three modal lognormal size distributions were fitted to the average size distributions for different potential temperature intervals, showing that the shape of the size distribution of the stratospheric ice clouds are similar to those observed in the upper troposphere. In the tropical troposphere the effective radius of the ice cloud particles decreases from 100 μm at about 10 km altitude, to 3 μm at the tropopause, while the ice water content decreases from 0.04 to 10−5 g m−3. No clear trend in the number concentration was observed with altitude, due to the thin and inhomogeneous characteristics of the observed cirrus clouds. The ice water content calculated from the observed ice crystal size distribution is compared to the ice water content derived from two hygrometer instruments. This independent measurement of the ice water content agrees within the combined uncertainty of the instruments for ice water contents exceeding 3×10−4g m−3. Stratospheric residence times, calculated based on gravitational settling, and evaporation rates show that the ice crystals observed in the stratosphere over the Hector storm system had a high potential of humidifying the stratosphere locally. Utilizing total aerosol number concentration measurements from a four channel condensation particle counter during two separate campaigns, it can be shown that the fraction of ice particles to the number of aerosol particles remaining ranges from 1:300 to 1:30 000 for tropical upper tropospheric ice clouds with ambient temperatures below −75°C.
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Achtert, P., M. Karlsson Andersson, F. Khosrawi y J. Gumbel. "Do tropospheric clouds influence Polar Stratospheric cloud occurrence in the Arctic?" Atmospheric Chemistry and Physics Discussions 11, n.º 12 (7 de diciembre de 2011): 32065–84. http://dx.doi.org/10.5194/acpd-11-32065-2011.
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Abstract. The type of Polar stratospheric clouds (PSCs) as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions in the polar stratosphere. The formation of PSCs depends strongly on temperature. However, the mechanisms of the formation of solid PSCs are still poorly understood. Recent satellite studies of Antarctic PSCs have shown that their formation can be associated with deep-tropospheric clouds which have the ability to cool the lower stratosphere radiatively and/or adiabatically. In the present study, lidar measurements aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate whether the formation of Arctic PSCs can be associated with deep-tropospheric clouds as well. Deep-tropospheric cloud systems have a vertical extent of more than 6.5 km with a cloud top height above 7 km altitude. PSCs observed by CALIPSO during the Arctic winter 2007/2008 were classified according to their type (STS, NAT, or ice) and to the kind of underlying tropospheric clouds. Our analysis reveals that 172 out of 211 observed PSCs occurred in connection with tropospheric clouds. 72% of these 172 observed PSCs occured above deep-tropospheric clouds. We also find that the type of PSC seems to be connected to the characteristics of the underlying tropospheric cloud system. During the Arctic winter 2007/2008 PSCs consisting of ice were mainly observed in connection with deep-tropospheric cloud systems while no ice PSC was detected above cirrus. Furthermore, we find no correlation between the occurrence of PSCs and the top temperature of tropospheric clouds. These findings suggest that Arctic PSC formation is connected to adiabatice cooling, i.e. dynamic effects rather than radiative cooling.
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Kirk-Davidoff, D. B. y J. F. Lamarque. "Maintenance of polar stratospheric clouds in a moist stratosphere". Climate of the Past 4, n.º 1 (31 de marzo de 2008): 69–78. http://dx.doi.org/10.5194/cp-4-69-2008.
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Abstract. Previous work has shown that polar stratospheric clouds (PSCs) could have acted to substantially warm high latitude regions during past warm climates such as the Eocene (55 Ma). Using a simple model of stratospheric water vapor transport and polar stratospheric cloud (PSC) formation, we investigate the dependence of PSC optical depth on tropopause temperature, cloud microphysical parameters, stratospheric overturning, and tropospheric methane. We show that PSC radiative effects can help slow removal of water from the stratosphere via self-heating. However, we also show that the ability of PSCs to have a substantial impact on climate depends strongly on the PSC particle number density and the strength of the overturning circulation. Thus even a large source of stratospheric water vapor (e.g. from methane oxidation) will not result in substantial PSC radiative effects unless PSC ice crystal number density is high compared to most current observations, and stratospheric overturning (which modulates polar stratospheric temperatures) is low. These results are supported by analysis of a series of runs of the NCAR WACCM model with methane concentrations varying up to one thousand times present levels.
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Kirk-Davidoff, D. B. y J. F. Lamarque. "Maintenance of polar stratospheric clouds in a moist stratosphere". Climate of the Past Discussions 3, n.º 4 (10 de julio de 2007): 935–60. http://dx.doi.org/10.5194/cpd-3-935-2007.
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Abstract. Previous work has shown that polar stratospheric clouds (PSCs) could have acted to substantially warm high latitude regions during past warm climates such as the Eocene (55 Ma). Using a simple model of stratospheric water vapor transport and polar stratospheric cloud (PSC) formation, we investigate the dependence of PSC optical depth on tropopause temperature, cloud microphysical parameters, stratospheric overturning, and tropospheric methane. We show that PSC radiative effects can help slow removal of water from the stratosphere via self-heating. However, we also show that the ability of PSCs to have a substantial impact on climate depends strongly on the PSC particle number density and the strength of the overturning circulation. Thus even a large source of stratospheric water vapor (e.g. from methane oxidation) will not result in substantial PSC radiative effects unless PSC ice crystal number density is high, and stratospheric overturning (which modulates polar stratospheric temperatures) is low. These results are supported by analysis of a series of runs of the NCAR WACCM model with methane concentrations varying up to one thousand times present levels.
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Khaykin, S. M., I. Engel, H. Vömel, I. M. Formanyuk, R. Kivi, L. I. Korshunov, M. Krämer et al. "Arctic stratospheric dehydration – Part 1: Unprecedented observation of vertical redistribution of water". Atmospheric Chemistry and Physics 13, n.º 22 (27 de noviembre de 2013): 11503–17. http://dx.doi.org/10.5194/acp-13-11503-2013.
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Abstract. We present high-resolution measurements of water vapour, aerosols and clouds in the Arctic stratosphere in January and February 2010 carried out by in situ instrumentation on balloon sondes and high-altitude aircraft combined with satellite observations. The measurements provide unparalleled evidence of dehydration and rehydration due to gravitational settling of ice particles. An extreme cooling of the Arctic stratospheric vortex during the second half of January 2010 resulted in a rare synoptic-scale outbreak of ice polar stratospheric clouds (PSCs) remotely detected by the lidar aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite. The widespread occurrence of ice clouds was followed by sedimentation and consequent sublimation of ice particles, leading to vertical redistribution of water inside the vortex. A sequence of balloon and aircraft soundings with chilled mirror and Lyman- α hygrometers (Cryogenic Frostpoint Hygrometer, CFH; Fast In Situ Stratospheric Hygrometer, FISH; Fluorescent Airborne Stratospheric Hygrometer, FLASH) and backscatter sondes (Compact Optical Backscatter Aerosol Detector, COBALD) conducted in January 2010 within the LAPBIAT (Lapland Atmosphere-Biosphere Facility) and RECONCILE (Reconciliation of Essential Process Parameters for an Enhanced Predictability of Arctic Stratospheric Ozone Loss and its Climate Interactions) campaigns captured various phases of this phenomenon: ice formation, irreversible dehydration and rehydration. Consistent observations of water vapour by these independent measurement techniques show clear signatures of irreversible dehydration of the vortex air by up to 1.6 ppmv in the 20–24 km altitude range and rehydration by up to 0.9 ppmv in a 1 km thick layer below. Comparison with space-borne Aura MLS (Microwave Limb Sounder) water vapour observations allow the spatiotemporal evolution of dehydrated air masses within the Arctic vortex to be derived and upscaled.
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Achtert, P., M. Karlsson Andersson, F. Khosrawi y J. Gumbel. "On the linkage between tropospheric and Polar Stratospheric clouds in the Arctic as observed by space–borne lidar". Atmospheric Chemistry and Physics 12, n.º 8 (25 de abril de 2012): 3791–98. http://dx.doi.org/10.5194/acp-12-3791-2012.
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Abstract. The type of Polar stratospheric clouds (PSCs) as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions in the polar stratosphere. The formation of PSCs depends strongly on temperature. However, the mechanisms of the formation of solid PSCs are still poorly understood. Recent satellite studies of Antarctic PSCs have shown that their formation can be associated with deep-tropospheric clouds which have the ability to cool the lower stratosphere radiatively and/or adiabatically. In the present study, lidar measurements aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate whether the formation of Arctic PSCs can be associated with deep-tropospheric clouds as well. Deep-tropospheric cloud systems have a vertical extent of more than 6.5 km with a cloud top height above 7 km altitude. PSCs observed by CALIPSO during the Arctic winter 2007/2008 were classified according to their type (STS, NAT, or ice) and to the kind of underlying tropospheric clouds. Our analysis reveals that 172 out of 211 observed PSCs occurred in connection with tropospheric clouds. 72% of these 172 observed PSCs occurred above deep-tropospheric clouds. We also find that the type of PSC seems to be connected to the characteristics of the underlying tropospheric cloud system. During the Arctic winter 2007/2008 PSCs consisting of ice were mainly observed in connection with deep-tropospheric cloud systems while no ice PSC was detected above cirrus. Furthermore, we find no correlation between the occurrence of PSCs and the top temperature of tropospheric clouds. Thus, our findings suggest that Arctic PSC formation is connected to adiabatice cooling, i.e. dynamic effects rather than radiative cooling.
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Xia, Yan, Yongyun Hu y Yi Huang. "Strong modification of stratospheric ozone forcing by cloud and sea-ice adjustments". Atmospheric Chemistry and Physics 16, n.º 12 (21 de junio de 2016): 7559–67. http://dx.doi.org/10.5194/acp-16-7559-2016.
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Abstract. We investigate the climatic impact of stratospheric ozone recovery (SOR), with a focus on the surface temperature change in atmosphere–slab ocean coupled climate simulations. We find that although SOR would cause significant surface warming (global mean: 0.2 K) in a climate free of clouds and sea ice, it causes surface cooling (−0.06 K) in the real climate. The results here are especially interesting in that the stratosphere-adjusted radiative forcing is positive in both cases. Radiation diagnosis shows that the surface cooling is mainly due to a strong radiative effect resulting from significant reduction of global high clouds and, to a lesser extent, from an increase in high-latitude sea ice. Our simulation experiments suggest that clouds and sea ice are sensitive to stratospheric ozone perturbation, which constitutes a significant radiative adjustment that influences the sign and magnitude of the global surface temperature change.
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de Reus, M., S. Borrmann, A. J. Heymsfield, R. Weigel, C. Schiller, V. Mitev, W. Frey et al. "Evidence for ice particles in the tropical stratosphere from in-situ measurements". Atmospheric Chemistry and Physics Discussions 8, n.º 6 (14 de noviembre de 2008): 19313–55. http://dx.doi.org/10.5194/acpd-8-19313-2008.
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Abstract. In-situ ice crystal size distribution measurements are presented within the tropical troposphere and lower stratosphere. The measurements were performed using a combination of a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) which were installed on the Russian high altitude research aircraft M55 "Geophysica" during the SCOUT-O3 campaign in Darwin, Australia. The objective of the campaign was to characterise the outflow of the Hector convective system, which appears on an almost daily basis during the pre-monsoon season over the Tiwi Islands, north of Darwin. In total 90 encounters with ice clouds, between 10 and 19 km altitude were selected from the dataset and were analysed. Six of these encounters were observed in the lower stratosphere, up to 1.4 km above the local tropopause, and were a result of overshooting convection. The ice crystals observed in the stratosphere comprise sizes up to 400 μm maximum dimension, include an ice water content of 0.1×10−3–1.7×10−3 g m−3 and were observed at ambient relative humidities (with respect to ice) between 75 and 157%. Three modal lognormal size distributions were fitted to the average size distributions for different potential temperature intervals, showing that the shape of the size distribution of the stratospheric ice clouds are similar to those observed in the upper troposphere. In the tropical troposphere the effective radius of the ice cloud particles decreases from 100 μm at about 10 km altitude, to 3 μm at the tropopause, while the ice water content decreases from 0.04 to 10−5 g m−3. No clear trend in the number concentration was observed with altitude, due to the thin and inhomogeneous characteristics of the observed cirrus clouds. The ice water content calculated from the observed ice crystal size distribution is compared to the ice water content derived from two hygrometer instruments. This independent measurement of the ice water content agrees within the combined uncertainty of the instruments for ice water contents exceeding 2×10−4 g m−3. Stratospheric residence times, calculated based on gravitational settling only, show that the ice crystals observed in the stratosphere over the Hector storm system have a high potential for humidifying the stratosphere. Utilizing total aerosol number concentration measurements from a four channel condensation particle counter, it can be shown that the fraction of activated ice particles with respect to the number of available aerosol particles ranges from 1:300 to 1:30 000 for tropical upper tropospheric ice clouds with ambient temperatures below −75°C.
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Thölix, L., L. Backman, R. Kivi y A. Karpechko. "Variability of water vapour in the Arctic stratosphere". Atmospheric Chemistry and Physics Discussions 15, n.º 16 (17 de agosto de 2015): 22013–45. http://dx.doi.org/10.5194/acpd-15-22013-2015.
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Abstract. This study evaluates the stratospheric water vapour distribution and variability in the Arctic. A FinROSE chemistry climate model simulation covering years 1990–2013 is compared to observations (satellite and frostpoint hygrometer soundings) and the sources of stratospheric water vapour are studied. According to observations and the simulations the water vapour concentration in the Arctic stratosphere started to increase after year 2006, but around 2011 the concentration started to decrease. Model calculations suggest that the increase in water vapour during 2006–2011 (at 56 hPa) is mostly explained by transport related processes, while the photochemically produced water vapour plays a relatively smaller role. The water vapour trend in the stratosphere may have contributed to increased ICE PSC occurrence. The increase of water vapour in the precense of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ICE PSCs in the Arctic vortex. The polar vortex was unusually cold in early 2010 and allowed large scale formation of the polar stratospheric clouds. The cold pool in the stratosphere over the Northern polar latitudes was large and stable and a large scale persistent dehydration was observed. Polar stratospheric ice clouds and dehydration were observed at Sodankylä with accurate water vapour soundings in January and February 2010 during the LAPBIAT atmospheric sounding campaign. The observed changes in water vapour were reproduced by the model. Both the observed and simulated decrease of the water vapour in the dehydration layer was up to 1.5 ppm.
Tesis sobre el tema "Stratospheric ice clouds"
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Mouzay, Julie. "Etude de l'évolution photochimique des aérosols de Titan". Electronic Thesis or Diss., Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0473.
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Cette thèse porte sur l’étude de l’évolution photochimique des aérosols présents dans la stratosphère de Titan. Au début de la saison automnale au pôle sud, la stratosphère, atteinte par des rayonnements FUV solaires, s’est refroidie et particulièrement enrichie en matériaux organiques : en aérosols, ainsi qu’en benzène (C6H6) et cyanure hydrogène (HCN), formés à haute altitude, qui ont été à l’origine de la formation de nuages de glace saisonniers. Expérimentalement, la photochimie de ces glaces, induite par des rayonnements UV similaires à ceux parvenant dans la basse stratosphère (l > 230 nm), conduit à la formation d’une phase volatile et d’une phase réfractaire qui représente en laboratoire un analogue des aérosols de la stratosphère de Titan formés par photo-polymérisation de glaces organiques. Nos résultats permettent de montrer que les propriétés spectroscopiques des analogues d’aérosols issus de la photolyse de glaces résultant de la condensation simultanée du benzène et du cyanure d’hydrogène sont similaires à celles des aérosols présents dans la stratosphère, d’après les données collectées par les spectromètres Cassini/VIMS et CIRS, à l’inverse des analogues produits par l’irradiation des glaces de benzène pur qui eux se différencient significativement des aérosols de la stratosphèreThis thesis deals with the study of the photochemical evolution of aerosols in Titan's stratosphere. At the beginning of the autumn season at the South Pole, the stratosphere, reached by FUV solar radiations, cooled and was particularly enriched in organic materials: aerosols as well as benzene (C6H6) and hydrogen cyanide (HCN), formed at high altitudes, and were responsible for the formation of seasonal ice clouds. Experimentally, the photochemistry of these systems, induced by UV radiations similar to those reaching the lower stratosphere (l > 230 nm), leads to the formation of a volatile phase and a refractory phase that represents experimentally an analogue of Titan stratospheric aerosols formed by polymerization of organic ice. Our results show that the spectroscopic properties of aerosols from the polymerization of ices of benzene mixed with hydrogen cyanide are more similar to aerosols present in the stratosphere, according to the data collected by the Cassini/VIMS and CIRS spectrometers, than those of aerosols produced by the irradiation of pure benzene ices
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Nankervis, Christopher James. "Co-located analysis of ice clouds detected from space and their impact on longwave energy transfer". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7755.
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A lack of quality data on high clouds has led to inadequate representations within global weather and climate models. Recent advances in spaceborne measurements of the Earth’s atmosphere have provided complementary information on the interior of these clouds. This study demonstrate how an array of space-borne measurements can be used and combined, by close co-located comparisons in space and time, to form a more complete representation of high cloud processes and properties. High clouds are found in the upper atmosphere, where sub-zero temperatures frequently result in the formation of cloud particles that are composed of ice. Weather and climate models characterise the bulk properties of these ice particles to describe the current state of the cloud-sky atmosphere. By directly comparing measurements with simulations undertaken at the same place and time, this study demonstrates how improvements can be made to the representation of cloud properties. The results from this study will assist in the design of future cloud missions to provide a better quality input. These improvements will also help improve weather predictions and lower the uncertainty in cloud feedback response to increasing atmospheric temperature. Most clouds are difficult to monitor by more than one instrument due to continuous changes in: large-scale and sub-cloud scale circulation features, microphysical properties and processes and characteristic chemical signatures. This study undertakes co-located comparisons of high cloud data with a cloud ice dataset reported from the Microwave Limb Sounder (MLS) instrument onboard the Aura satellite that forms part of the A-train constellation. Data from the MLS science team include vertical profiles of temperature, ice water content (IWC) and the mixing ratios of several trace gases. Their vertical resolutions are 3 to 6 km. Initial investigations explore the link between cloud-top properties and the longwave radiation budget, developing methods for estimating cloud top heights using; longwave radiative fluxes, and IWC profiles. Synergistic trios of direct and indirect high cloud measurements were used to validate detections from the MLS by direct comparisons with two different A-train instruments; the NASA Moderate-resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth’s Radiant Energy System (CERES) onboard on the Aqua satellite. This finding focuses later studies on two high cloud scene types that are well detected by the MLS; deep convective plumes that form from moist ascent, and their adjacent outflows that emanate outwards several hundred kilometres. The second part of the thesis identifies and characterises two different high cloud scenes in the tropics. Direct observational data is used to refine calculations of the climate sensitivity to upper tropospheric humidity and high cloud in different conditions. The data reveals several discernible features of convective outflows are identified using a large sample of MLS data. The key finding, facilitated by the use of co-location, reveals that deep convective plumes exert a large longwave warming effect on the local climate of 52 ± 28Wm−2, with their adjacent outflows presenting a more modest warming of 33 ± 20Wm−2.
Libros sobre el tema "Stratospheric ice clouds"
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Hallett, John. Replicator for characterization of cirrus and polar stratospheric cloud particles: Final report, NASA grant no. NAG 2-663. [Washington, DC: National Aeronautics and Space Administration, 1995.
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Facility, Dryden Flight Research, ed. A laboratory study on the phase transition for polar stratospheric cloud particles. Edwards, Calif: National Aeronautics and Space Administration, Dryden Flight Research Center, 1997.
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Facility, Dryden Flight Research, ed. A laboratory study on the phase transition for polar stratospheric cloud particles. Edwards, Calif: National Aeronautics and Space Administration, Dryden Flight Research Center, 1997.
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Hallett, John. Final report, nucleation and growth of crystals under cirrus and polar stratospheric cloud conditions (NASA grant no. NAG-W-2572. [Washington, DC: National Aeronautics and Space Administration, 1995.
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B, Toon O., Hamill Patrick y United States. National Aeronautics and Space Administration., eds. Freezing behavior of stratospheric sulfate aerosols inferred from trajectory studies. [Washington, D.C: National Aeronautics and Space Administration, 1995.
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United States. National Aeronautics and Space Administration., ed. The in-flight calibration of the Hubble Space Telescope attitude sensors. [Washington, DC: National Aeronautics and Space Administration, 1991.
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Spectroscopic evidence against nitric accide trlhydrate in polar stratospheric clouds. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1995.
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Spectroscopic evidence against nltric [i.e. nitric] acid trlhydrate [i.e. trihydrate] in polar stratospheric clouds. [Washington, D.C: National Aeronautics and Space Administration, 1995.
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The in-flight calibration of the Hubble Space Telescope attitude sensors. [Washington, DC: National Aeronautics and Space Administration, 1991.
Buscar texto completoCapítulos de libros sobre el tema "Stratospheric ice clouds"
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Peter, Thomas. "Physico-Chemistry of Polar Stratospheric Clouds". En Ice Physics and the Natural Environment, 143–67. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-642-60030-2_9.
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Peter, Th y M. Baker. "Lifetimes of Ice Crystals in the Upper Troposphere and Stratosphere". En Clouds, Chemistry and Climate, 57–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-61051-6_4.
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DeMott, Paul. "Laboratory Studies of Cirrus Cloud Processes". En Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0009.
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A number of processes that play a role in the formation, evolution of microphysical properties, and radiative characteristics of cirrus clouds are amenable to investigation in a laboratory setting. These laboratory studies provide fundamental data for quantifying and validating theoretical concepts and help guide investigations involving direct and remote measurements of cirrus. Laboratory data also may be used for formulating parameterizations for numerical cloud models, especially where information is incomplete or full descriptions are not possible. This chapter reviews results from laboratory studies of ice formation, ice crystal growth, radiative transfer, and aerosol scavenging and transformation in the cirrus environment. Emphasis is placed on ice formation in cirrus conditions. The related topic of contrail formation is covered separately in this book. The formation mechanisms of lower stratospheric clouds are reviewed elsewhere (e.g., Tolbert 1994; Peter 1996; Carslaw et al. 1997; Koop et al. 1997a). Laboratory studies of cirrus ice formation are at a rapidly developing stage, so it is useful to provide significant background bases for current and needed studies. Key issues are aerosol composition, ice nucleation mechanisms, and the synergy between theory and laboratory measurements. Vali (1996), Baker (1997) and Martin (2000) discuss some of these issues in review papers. Upper tropospheric aerosol particles play an important catalytic role in the formation of cirrus. The nucleation process is important in determining the microphysical properties of cirrus. Numerical modeling studies (e.g., Jensen and Toon 1994; DeMott et al. 1994, 1997; Heymsfield and Sabin 1989) indicate that variation in the factors that drive the nucleation of ice and variations in the physical and chemical characteristics of aerosol particle populations lead to the formation of cirrus with different microphysical characteristics. Knowledge of the physics and chemistry of aerosols in the upper troposphere and lower stratosphere has evolved at a rapid pace. A detailed accounting of this topic is beyond the scope of this chapter. For the purpose of the present discussion, it is sufficient to note that the aerosol from which cirrus nucleate may vary significantly from place to place. Differences in aerosol properties in time and space occur because particles can arrive to the upper troposphere in so many ways and from so many sources.
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Lynch, David K. y Kenneth Sassen. "Subvisual Cirrus". En Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0016.
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Starting during World War II, pilots flying high over the tropics reported “a thin layer of cirrus 500ft above us”. Yet as they ascended, they still observed more thin cirrus above them, leading to the colloquialism “cirrus evadus.” With the coming of lidar in the early 1960s, rumors and unqualified reports of subvisual cirrus were replaced with validated detections, in situ sampling, and the first systematic studies (Uthe 1977; Barnes 1980, 1982). Heymsfield (1986) described observations over Kwajalein Atoll in the western tropical Pacific Ocean, where pilots and lidars could clearly see the cloud but DMSP (U.S. Defense Meteorological Satellite Program) radiance measurements and ground observers could not. The term “subvisual” is a relatively recent appellation. Prior terminology included cirrus haze, semitransparent cirrus, subvisible cirrus veils, low density clouds, fields of ice aerosols, cirrus, anvil cirrus, and high altitude tropical (HAT) cirrus. Subvisual cirrus clouds (SVC) are widespread (Winker and Trepte 1998; see chapter 12, this volume) and virtually undetectable with existing passive sensors. Orbiting solar limb occupation systems such as the Stratospheric Aerosol and Gas Experiment (SAGE) can detect these clouds, but only by looking at them horizontally where the optical depths are significant. SVC appear to affect climate primarily by heating the planet, though to what extent this may happen is unknown. Much of what we know is based on work by Heymsfield (1986), Platt et al. (1987), Sassen et al. (1989, 1992), Flatau et al. (1990), Liou et al. (1990), Hutchinson et al. (1991, 1993), Dalcher (1992), Sassen and Cho (1992), Takano et al. (1992), Lynch (1993), Schmidt et al. (1993), Schmidt and Lynch (1995), and Winker and Trepte (1998). SVC are defined as any high clouds composed primarily of ice (WMO 1975) and whose vertical visible optical depth is 0.03 or less (Sassen and Cho 1992). Such clouds are usually found near the tropopause and are less than about 1 km thick vertically. SVC do not appear to be fundamentally different from ordinary, optically thicker cirrus. They do, however, differ from average cirrus by being colder (-50-90°C), thinner (<0.03 optical depths at 0.694 μm), and having smaller particles (typically about <50μm diameter).
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Liou, K. N. y Y. Gu. "Radiative Transfer in Cirrus Clouds: Light Scatting and Spectral Information". En Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0017.
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The importance of cirrus clouds in climate has been recognized in the light of a number of intensive composite field observations: the First ISCCP Regional Experiment (FIRE) I in October-November 1986; FIRE II in November-December 1991; the European experiment on cirrus (ICE/EUCREX) in 1989; Subsonic Aircraft: Contrail and Cloud Effect Special Study (SUCCESS) in April 1996. Based on observations from the ground-based lidar and radar, airborne instrumentation, and satellites, cirrus clouds are typically located in the upper troposphere and lower stratosphere (Liou 1986). The formation, maintenance, and dissipation of cirrus clouds are directly associated with synoptic and mesoscale disturbances as well as related to deep cumulus outflows. Increases of high cloud cover have been reported at a number of urban airports in the United States based on surface observations spanning 40 years (Liou et al. 1990; Frankel et al. 1997). These increases have been attributed to the contrails and water vapor produced by jet airplane traffic. Satellite observations from NOAA polar-orbiting High-Resolution Infrared Radiation Sounder (HIRS) using the CO2 slicing method (Wylie et al. 1994) also show that cirrus cloud cover substantially increased between 60° S and 60° N during a 4-year period from June 1989 to September 1993. Understanding the role of cirrus clouds in climate must begin with reliable modeling of their radiative properties for incorporation in climate models as well as determination of the global variability of their composition, structure, and optical properties. Development of the remote sensing methodologies for the detection and retrieval of the ubiquitous visible and subvisual cirrus clouds requires the basic scattering, absorption, and polarization data for ice crystals in conjunction with appropriate radiative transfer models. We present the fundamentals involving radiative transfer in cirrus clouds and review pertinent research. In section 13.1, an overview of the subject of light scattering by ice crystals is presented in which we discuss a unification of the geometric optics approach for large ice particles and the finite-difference time domain numerical solution for small ice particles, referred to as the unified theory. Section 13.2 presents radiative transfer in cirrus clouds involving two unique properties: orientation of nonspherical ice crystals and cloud inhomogeneity.
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Ansmann, Albert. "Molecular-Backscatter Lidar Profiling of the Volume-Scattering Coefficient in Cirrus". En Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0013.
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Backscatter and polarization lidars have already been used extensively to investigate ice clouds (see chapters 2 and 10). A severe limitation is that trustworthy values of the volume-scattering coefficient, one of the most important parameters in the description of the impact of cirrus on climate, cannot be derived from data taken with these lidars. Even the retrieved cirrus backscatter-coefficient profile is often questionable. A discussion of achievements and limitations of the lidar method can be found in the literature (e.g., Fernald et al. 1972; Klett 1981; Fernald 1984; Klett 1985; Sasano et al. 1985; Bissonnette 1986; Ansmann et al. 1992b; Kovalev 1995). The procedure, with all its subsequent modifications and improvements, suffers from the fact that two physical quantities, the particle backscatter coefficient and the particle extinction coefficient, must be determined from only one lidar signal. The uncertainties in the estimated optical parameters are especially large in cirrus, in which the relationship between particle extinction and backscattering can vary strongly in space and time. The situation improved significantly when the first molecular (Raman)-backscatter lidar experiments demonstrated that accurate extinction profiling throughout the entire troposphere is possible (Ansmann et al. 1990, 1992b). After the Pinatubo eruption, it was shown that even at stratospheric heights profiles of the volume-scattering coefficient can easily be obtained with a Raman lidar (Ansmann et al. 1991, 1993a, 1997; Ferrare et al. 1992; Gross et al. 1995; Donavan und Carswell 1997). Two types of molecular-backscatter lidars for extinction measurements are available. The Raman lidar measures lidar return signals elastically backscattered by air molecules and particles and inelastically (Raman) backscattered by nitrogen and/or oxygen molecules (Cooney et al. 1969; Melfi 1972; Ansmann et al. 1992a; Whiteman et al. 1992; Reichardt et al. 1996). Interference-filter polychromators and double-grating monochromators (Arshinov et al. 1983; Wandinger et al. 1998) are used to separate the aerosol signal from the vibrational-rotational or pure rotational Raman signals, to reduce the sky background radiation, and, for the Raman channels, to block the strong elastic-backscatter radiation at the laser wavelength. The suppression has to be better than 10-8. The second type of a molecular-backscatter lidar is the High Spectral Resolution Lidar (HSRL).
Actas de conferencias sobre el tema "Stratospheric ice clouds"
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Tolbert, Margaret A. "FTS Measurements of Aerosols". En Fourier Transform Spectroscopy. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/fts.1995.ffa2.
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Heterogeneous reactions on polar stratospheric clouds (PSCs) have recently been implicated in Arctic and Antarctic ozone destruction. Although the chemistry is now well documented, there are still major uncertainties in the chemical composition and formation mechanism for PSCs. PSCs are usually classified as type I or type II, depending on their formation temperature. Type II PSCs are composed of crystalline water ice and form only when stratospheric temperatures drop below about 188 K. These clouds are most frequently observed in the Antarctic winter stratosphere. In contrast, Type I PSCs form at temperatures several degrees warmer than the frost point and are therefore observed in both polar stratospheres. Although type I PSCs are thought to contain HNO3 and water, the exact chemical composition has not been established.
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Farley, R., J. W. Meriwether, R. McNutt, P. Dao, W. Moskowitz, G. Davidson, Ib Mikkelsen y M. Larsen. "Raman/Rayleigh lidar measurements during a major stratwarm in Greenland". En Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/orsa.1991.otua4.
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Rayleigh lidar observations of atmospheric temperatures below 30 km are contaminated by the Mie backscattering from the sulphate stratospheric aerosols that normally exist between 12 and 25 km. Consequently, the fact that nitrogen Raman lidar returns for vibrational and rotational Raman backscattering are red-shifted offers the opportunity to extend the Rayleigh lidar measurements to lower altitudes by joining the two relative density profiles at a height where the Mie backscattering contamination may be ignored. This technique was applied by us previously with the aim of providing an improved means of normalizing lidar measurements of upper atmosphere densities against simultaneous balloon measurements. Because lower stratosphere temperatures below 195 °K will support the production of polar stratospheric clouds (PSC) designated as Type 2 nitric acid trihydrate (NAT) and for temperatures below the frost point, nominally 190 °K, the production of Type 1 water ice PSCs. To study the possible formation and evolution of these polar stratospheric clouds, we undertook to make measurements of temperatures in the winter Arctic with a Raman augmentation of our mobile Rayleigh lidar facility. While the results did not show any indications of the production of PSCs, the profiles did show substantial dynamic activity in connection with the progression of a major stratospheric warming.
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Khmelevtsov, S. S. y Yu G. Kaufman. "Stratospheric aerosol measuring from Obninsk lidar station following the volcano Pinatubo eruption". En Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/orsa.1993.the.22.
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The eruption effect on stratospheric aerosol was first observed during lidar sounding at Obninsk station (55°N, 37°E ) in 37 days following the eruption, 22 of July , 1991. The devices used for sounding are described in [1]. The speed of cloud movement, computed on the given measurements, has been found to be more than 1 degree per twenty four hours. 21 of February, 1992 the integral backscatter reached the value 3,67 10−3 Br−1 ( the measurements were carried out at the wavelength of 532 nm ) in the layer of 15-30 km and than began to decrease. According to preliminary results the time of relaxation of the stratospheric aerosol in latitude 55°North is close to 10 months, i.e. just less than the relaxation time of the stratospheric aerosol formed following volcano El Chichon in 1982.
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Reichardt, J. y C. Weitkamp. "Raman-DIAL Measurements in the Upper Troposphere and Stratosphere: The Effect of High-Altitude Ice Clouds on Ozone". En Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/orsa.1997.othc.1.
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For many years lidar systems have proved to be valuable tools for the measurement of atmospheric data with high spatial and temporal resolution. The lidar variant used so far for ozone height profiling has been known as the differential absorption and scattering, or DIAL, technique.1 In DIAL two light pulses of different wavelengths are transmitted into the atmosphere, the elastically backscattered return signals are registered, and the ozone concentration is calculated from the difference of optical absorption by ozone at the two wavelengths. However, due to elastic particle scattering DIAL measurements are hardly possible in altitudes with enhanced particle content. The influence of particle scattering on the retrieval of ozone concentrations from measured lidar profiles can be reduced substantially if inelastic molecular return signals of a gas such as nitrogen are used instead of the elastic lidar returns. This so-called Raman-DIAL technique2 has been implemented in the GKSS Raman lidar in spring 1994.3 A XeCl excimer laser and a frequency-tripled Nd:YAG laser serve as light sources, and the return signals at the nitrogen Raman wavelengths are used for the calculation of ozone concentration profiles. In addition, tropospheric water vapor and backscatter and extinction properties of atmospheric particles are obtained with the Raman-lidar technique. Elastic depolarization ratios are measured as well. Whereas the conventional DIAL and the Raman lidar techniques have undergone an extensive error analysis,4,5 an error treatment of the Raman-DIAL technique has not been published so far. In the present contribution an outline of a Raman-DIAL error analysis is given. As space is limited, only ozone measurements in the free troposphere in the presence of cirrus clouds are considered.