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1
Kozlovsky, A., S. Shalimov, J. Kero, T. Raita e M. Lester. "Multi-Instrumental Observations of Nonunderdense Meteor Trails". Journal of Geophysical Research: Space Physics 123, n. 7 (luglio 2018): 5974–89. http://dx.doi.org/10.1029/2018ja025405.
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Moreno-Ibáñez, Manuel, Josep M. Trigo-Rodríguez, José María Madiedo, Jérémie Vaubaillon, Iwan P. Williams, Maria Gritsevich, Lorenzo G. Morillas et al. "Multi-instrumental observations of the 2014 Ursid meteor outburst". Monthly Notices of the Royal Astronomical Society 468, n. 2 (9 marzo 2017): 2206–13. http://dx.doi.org/10.1093/mnras/stx592.
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Nakariakov, V. M., M. K. Kosak, D. Y. Kolotkov, S. A. Anfinogentov, P. Kumar e Y. J. Moon. "Properties of Slow Magnetoacoustic Oscillations of Solar Coronal Loops by Multi-instrumental Observations". Astrophysical Journal 874, n. 1 (19 marzo 2019): L1. http://dx.doi.org/10.3847/2041-8213/ab0c9f.
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Parker, Q. A., e F. G. Watson. "A Flair for Multi-Object Spectroscopy". Symposium - International Astronomical Union 161 (1994): 85–88. http://dx.doi.org/10.1017/s0074180900047124.
Testo completoAbstract (sommario):
Unique in the regime of wide-field astronomy is the multi-object spectroscopy system ‘FLAIR’ developed for the UK Schmidt Telescope (UKST). The current system can perform simultaneous observations of ∼ 90 objects across 40 sq. degrees of sky. FLAIR has given a whole new platform for performing astronomical observations with a Schmidt telescope in a non-photographic role. The system is simple to operate, highly stable, easy to interchange with standard photography and outclasses single-object spectroscopy systems on 2.0 m class telescopes for many types of observation. The system has continued to be developed to enhance its flexibility, robustness and versatility, culminating recently in the commissioning of new fibre feeds and formats. The facility to observe independent standard stars, and the capability of observing objects in two UKST fields in a single night has recently been demonstrated. FLAIR is a powerful, cost-effective addition to the instrumental repertoire of the Anglo-Australian Observatory in a way that was not even remotely envisaged when the UKST was built.
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Liu, Lei, Yibin Yao e Ercha Aa. "Multi-Instrumental Observations of Early Morning Equatorial Plasma Depletions During the 2017 Memorial Weekend Storm". IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 13 (2020): 5351–57. http://dx.doi.org/10.1109/jstars.2020.3022748.
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Ramaprakash, A. N., S. N. Tandon e R. Gupta. "Imaging Polarimetry of Nearby Molecular Clouds". International Astronomical Union Colloquium 166 (1997): 243–46. http://dx.doi.org/10.1017/s0252921100071050.
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AbstractIn order to study the role played by the magnetic fields in the dynamics of the interstellar medium (ISM) a two-channel imaging polarimeter (IMPOL) has been constructed. The instrument is capable of multi-wavelength observations in the visible and very near infrared (IR) wavelengths, has a sensitive CCD detector and a built-in acquisition and guidance unit. When used with a 1.2m, f/13 telescope IMPOL gives a field of view of 6 × 6 arcmin with an angular resolution of 2" so that it is well-suited to observe both faint extended objects and moderately crowded stellar fields. The instrumental polarization is less than 0.05% and the accuracy of the measurements is primarily limited by photon noise in a typical observation. In this paper, we present a brief description of the instrument and observational techniques, as well as the results of a successful observation of a molecular cloud close to the open cluster IC 5146.
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Szkop, Artur, Alnilam Fernandes e Aleksander Pietruczuk. "Towards a Multi-Instrumental Approach to Closing Aerosol Optical Extinction Profiles". Atmosphere 13, n. 9 (6 settembre 2022): 1443. http://dx.doi.org/10.3390/atmos13091443.
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A novel methodology is formulated and investigated on test cases for the reconstruction of complete vertical aerosol extinction profiles in which a synergy of remote, in-situ, and airborne measurements is utilized. The GRASP Open aerosol retrieval algorithm is supplied with remote LIDAR and sunphotometer data to obtain aerosol extinction profiles within the LIDAR’s operation range for coarse and fine aerosol modes separately. These are supplemented with ground-based in-situ measurements of particle size distribution that are translated to coarse and fine aerosol extinction coefficients with the use of Mie theory. UAV-based observations with optical particle counters are included to add information on vertical aerosol variability in the near-surface region. The profiles are closed with an analytical interpolation that is fine-tuned to produce continuous and smooth extinction profiles throughout the whole troposphere that are in agreement with columnar aerosol optical depth measurements. We present the possibility of reconstructing a complete and calibrated aerosol extinction profile, based on the case studies at a Central European background station. We include data-denial experiments to show that the inclusion of UAV-based measurements improves such reconstructions by providing crucial information on aerosol profiles near the ground. The proposed methodology can prove to be a potent tool for studies of aerosol concentration and evolution, especially when the majority of the pollution resides near the surface. Such conditions are prevalent in many highly industrialized regions, including central and southern Poland.
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Kaltman, T. I., A. G. Stupishin, S. A. Anfinogentov, V. M. Nakariakov, M. A. Loukitcheva e A. V. Shendrik. "Hot Jets in the Solar Corona: Creating a Catalogue of Events Based on Multi-Instrumental Observations". Geomagnetism and Aeronomy 61, n. 7 (dicembre 2021): 1083–91. http://dx.doi.org/10.1134/s0016793221070070.
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Astafyeva, E., I. Zakharenkova, J. D. Huba, E. Doornbos e J. van den IJssel. "Global Ionospheric and Thermospheric Effects of the June 2015 Geomagnetic Disturbances: Multi-Instrumental Observations and Modeling". Journal of Geophysical Research: Space Physics 122, n. 11 (novembre 2017): 11,716–11,742. http://dx.doi.org/10.1002/2017ja024174.
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Bothe, Oliver, Sebastian Wagner e Eduardo Zorita. "Inconsistencies between observed, reconstructed, and simulated precipitation indices for England since the year 1650 CE". Climate of the Past 15, n. 1 (15 febbraio 2019): 307–34. http://dx.doi.org/10.5194/cp-15-307-2019.
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Abstract. The scarcity of long instrumental records, uncertainty in reconstructions, and insufficient skill in model simulations hamper assessing how regional precipitation changed over past centuries. Here, we use standardized precipitation data to compare a regional climate simulation, reconstructions, and long observational records of seasonal (March to July) mean precipitation in England and Wales over the past 350 years. The Standardized Precipitation Index is a valuable tool for assessing agreement between the different sources of information, as it allows for a comparison of the temporal evolution of percentiles of the precipitation distributions. These evolutions are not consistent among reconstructions, a regional simulation, and instrumental observations for severe and extreme dry and wet conditions. The lack of consistency between the different data sets may be due to the dominance of internal climate variability over the impact of natural exogenous forcing conditions on multi-decadal timescales. The disagreement between sources of information reduces our confidence in inferences about the origins of hydroclimate variability for small regions. However, it is encouraging that there is still some agreement between a regional simulation and observations. Our results emphasize the complexity of hydroclimate changes during the recent centuries and stress the necessity of a thorough understanding of the processes affecting forced and unforced precipitation variability.
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Rang, Xinyi, Chao Xiong, Yuhao Zheng, Jing Liu, Yu Jiao, Shunzu Gao, Yuyang Huang, Xin Wan e Fan Yin. "Multi-instrumental observations of nighttime X-pattern of equatorial ionization anomaly during magnetically quiet-time: case study". Earth and Planetary Physics 8, n. 6 (2024): 0. http://dx.doi.org/10.26464/epp2024072.
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Tritakis, Vasilis, Janusz Mlynarczyk, Ioannis Contopoulos, Jerzy Kubisz, Vasilis Christofilakis, Giorgos Tatsis, Spyridon K. Chronopoulos e Christos Repapis. "Extremely Low Frequency (ELF) Electromagnetic Signals as a Possible Precursory Warning of Incoming Seismic Activity". Atmosphere 15, n. 4 (7 aprile 2024): 457. http://dx.doi.org/10.3390/atmos15040457.
Testo completoAbstract (sommario):
We analyzed a large number (77) of low-to-medium-magnitude earthquakes (M3.5–M6.5) that occurred within a period of three years (2020–2022) in the Southern half of Greece in relation to the ELF activity in that region and time period. In most cases, characteristic ELF signals appear up to 20 days before the earthquakes. This observation may add an important new element to the Lithospheric–Atmospheric–Ionospheric scenario, thus contributing to a better prediction of incoming earthquakes. We discuss the role of ELF observations in reliable seismic forecasting. We conclude that the magnitude of an earthquake larger than M4.0 and the distance of the epicenter shorter than 300 km from the recording site is needed for typical pre-seismic signals to be observed. Finally, we remark that a reliable prediction of earthquakes could result from an integrated project of multi-instrumental observations, where all the known variety of precursors would be included, and the whole data set would be analyzed by advanced machine learning methods.
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Chane Ming, Fabrice, Alain Hauchecorne, Christophe Bellisario, Pierre Simoneau, Philippe Keckhut, Samuel Trémoulu, Constantino Listowski et al. "Case Study of a Mesospheric Temperature Inversion over Maïdo Observatory through a Multi-Instrumental Observation". Remote Sensing 15, n. 8 (12 aprile 2023): 2045. http://dx.doi.org/10.3390/rs15082045.
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The dynamic vertical coupling in the middle and lower thermosphere (MLT) is documented over the Maïdo observatory at La Réunion island (21°S, 55°E). The investigation uses data obtained in the framework of the Atmospheric dynamics Research InfraStructure in Europe (ARISE) project. In particular, Rayleigh lidar and nightglow measurements combined with other observations and modeling provide information on a mesospheric inversion layer (MIL) and the related gravity waves (GWs) on 9 and 10 October 2017. A Rossby wave breaking (RWB) produced instabilities in the sheared background wind and a strong tropospheric activity of GWs on 9–11 October above La Réunion. The MIL was observed on the night of 9 October when a large amount of tropospheric GWs propagated upward into the middle atmosphere and disappeared on 11 October when the stratospheric zonal wind filtering became a significant blocking. Among other results, dominant mesospheric GW modes with vertical wavelengths of about 4–6 km and 10–13 km can be traced down to the troposphere and up to the mesopause. Dominant GWs with a wavelength of ~2–3 km and 6 km also propagated upward and eastward from the tropospheric source into the stratosphere on 9–11 October. Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature and OH profiles indicate that GW activity in the middle atmosphere affects the upper atmosphere with waves breaking at heights below the MIL and in the mesopause. Several techniques are illustrated on nightglow images to access GW activity and spectral characteristics at the mesopause for high and low frequency GWs on the nights of 9–10 October. In conclusion, intense tropospheric activity of GWs induced by RWB events can be linked with MILs at the subtropical barrier in the South-West Indian Ocean during austral winter.
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Abe, S., J. Abhir, A. Abhishek, F. Acero, A. Acharyya, R. Adam, A. Aguasca-Cabot et al. "Dark matter line searches with the Cherenkov Telescope Array". Journal of Cosmology and Astroparticle Physics 2024, n. 07 (1 luglio 2024): 047. http://dx.doi.org/10.1088/1475-7516/2024/07/047.
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Abstract Monochromatic gamma-ray signals constitute a potential smoking gun signature for annihilating or decaying dark matter particles that could relatively easily be distinguished from astrophysical or instrumental backgrounds. We provide an updated assessment of the sensitivity of the Cherenkov Telescope Array (CTA) to such signals, based on observations of the Galactic centre region as well as of selected dwarf spheroidal galaxies. We find that current limits and detection prospects for dark matter masses above 300 GeV will be significantly improved, by up to an order of magnitude in the multi-TeV range. This demonstrates that CTA will set a new standard for gamma-ray astronomy also in this respect, as the world's largest and most sensitive high-energy gamma-ray observatory, in particular due to its exquisite energy resolution at TeV energies and the adopted observational strategy focussing on regions with large dark matter densities. Throughout our analysis, we use up-to-date instrument response functions, and we thoroughly model the effect of instrumental systematic uncertainties in our statistical treatment. We further present results for other potential signatures with sharp spectral features, e.g. box-shaped spectra, that would likewise very clearly point to a particle dark matter origin.
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van der Hulst, Marije, Rianne Kok, Peter Prinzie, Eric A. P. Steegers e Loes C. M. Bertens. "Early Maternal Caregiving Capacities in Highly Vulnerable, Multi-Problem Families". International Journal of Environmental Research and Public Health 19, n. 23 (2 dicembre 2022): 16130. http://dx.doi.org/10.3390/ijerph192316130.
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Caregiving capacities may be an important link between multi-problem circumstances and adverse child development. This study aims to assess caregiving capacities and their correlations in highly vulnerable, multi-problem families in Rotterdam, the Netherlands. Caregiving capacity (overall, emotional and instrumental) was prospectively assessed in 83 highly vulnerable women using video-observations of daily caregiving tasks, six week postpartum. Supporting data were collected at three time points: at inclusion, six weeks after inclusion and six weeks postpartum, and these included psychological symptoms, self-sufficiency, problematic life domains, home environment, income, depression, anxiety and stress. Pregnancy- and delivery-related information was collected from obstetric care professionals. Maternal caregiving scores averaged below adequate quality. Mothers living in an unsafe home environment (B = 0.62) and mothers with more problematic life domains (≤3 domains, B = 0.32) showed significantly higher instrumental caregiving capacities. Other variables were not related to caregiving capacities. Caregiving capacity in this highly vulnerable population was below adequate quality. However, in most cases there was no significant association between caregiving and the variables related to vulnerability. This means that a potential association between vulnerability and caregiving capacities might be driven by the interaction between several problems, rather than the type or number of problems.
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Ilyas, Maryam, Douglas Nychka, Chris Brierley e Serge Guillas. "Global ensemble of temperatures over 1850–2018: quantification of uncertainties in observations, coverage, and spatial modeling (GETQUOCS)". Atmospheric Measurement Techniques 14, n. 11 (12 novembre 2021): 7103–21. http://dx.doi.org/10.5194/amt-14-7103-2021.
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Abstract. Instrumental global temperature records are derived from the network of in situ measurements of land and sea surface temperatures. This observational evidence is seen as being fundamental to climate science. Therefore, the accuracy of these measurements is of prime importance for the analysis of temperature variability. There are spatial gaps in the distribution of instrumental temperature measurements across the globe. This lack of spatial coverage introduces coverage error. An approximate Bayesian computation based multi-resolution lattice kriging is developed and used to quantify the coverage errors through the variance of the spatial process at multiple spatial scales. It critically accounts for the uncertainties in the parameters of this advanced spatial statistics model itself, thereby providing, for the first time, a full description of both the spatial coverage uncertainties along with the uncertainties in the modeling of these spatial gaps. These coverage errors are combined with the existing estimates of uncertainties due to observational issues at each station location. It results in an ensemble of 100 000 monthly temperatures fields over the entire globe that samples the combination of coverage, parametric and observational uncertainties from 1850 to 2018 over a 5∘×5∘ grid.
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Santos, Larissa, Jian Yao, Le Zhang, Shamik Ghosh, Pengjie Zhang, Wen Zhao, Thyrso Villela, Jiming Chen e Jacques Delabrouille. "Testing the analytical blind separation method in simulated CMB polarization maps". Astronomy & Astrophysics 650 (giugno 2021): A65. http://dx.doi.org/10.1051/0004-6361/201936546.
Testo completoAbstract (sommario):
Context. Multi-frequency observations are needed to separate the cosmic microwave background (CMB) from foreground emission and accurately extract cosmological information from the data. The analytical blind separation (ABS) method is dedicated to extracting the CMB power spectrum from multi-frequency observations in the presence of contamination from astrophysical foreground emission and instrumental noise. Aims. In this study, we apply the ABS method to simulated sky maps as could be observed with a future space-borne survey in order to test its capability of determining the CMB polarization E- and B-mode power spectra. Methods. We present the ABS method performance on simulations for both a full-sky analysis and for an analysis concentrating on sky regions less impacted by Galactic foreground emission. Results. We discuss the origin and minimization of biases in the estimated CMB polarization angular power spectra. We find that the ABS method performs quite well for the analysis of full-sky observations at intermediate and small angular scales, in spite of strong foreground contamination. On the largest scales, extra work is still required to reduce biases of various origins and the impact of confusion between CMB E and B polarization for partial sky analyses.
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Ye, Hailun, Wen Yi, Baozhu Zhou, Jianfei Wu, Bingkun Yu, Penghao Tian, Jianyuan Wang et al. "Multi-Instrumental Observations of Midlatitude Plasma Irregularities over Eastern Asia during a Moderate Magnetic Storm on 16 July 2003". Remote Sensing 15, n. 4 (20 febbraio 2023): 1160. http://dx.doi.org/10.3390/rs15041160.
Testo completoAbstract (sommario):
This study presents the observations of midlatitude plasma irregularities over Eastern Asia during a moderate magnetic storm on 16 July 2003. Multi-instrumental observations, including the ground-based ionosondes, the GNSS networks, and the CHAMP and ROCSAT-1 satellites, were utilized to investigate the occurrence and characteristics of midlatitude plasma irregularities. The midlatitude strong spread F (SSF) mainly occurred in the midnight–morning sector as observed by ionosondes over Japan during this storm. SSF was related to plasma depletions, which is also recorded by GNSS network in the form of the enhancement of the rate of total electron content (TEC) change index (ROTI). The possible mechanism for the generation of SSF is that the enhanced eastward electric fields, associated with the prompt penetration electric fields and disturbance dynamo electric fields, cause the uplift and latitudinal extension of equatorial plasma bubbles (EPBs) to generate the observed midlatitude SSF further. Meanwhile, plasma density increased significantly under the influence of this storm. In addition, other common type of spread F, frequency spread F (FSF), was observed over Japan on the non-storm day and/or at high latitude station WK545, which seems to be closely related to the coupling of medium-scale traveling ionospheric disturbances (MSTIDs) and sporadic E (Es) layer. The above results indicate that various types of midlatitude spread F can be produced by different physical mechanisms. It is found that SSF can significantly affect the performance of radio wave propagation compared with FSF. Our results show that space weather events have a significant influence on the day-to-day variability of the occurrence and characteristics of ionospheric F-region irregularities at midlatitudes.
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Piersanti, Mirko, Massimo Materassi, Roberto Battiston, Vincenzo Carbone, Antonio Cicone, Giulia D’Angelo, Piero Diego e Pietro Ubertini. "Magnetospheric–Ionospheric–Lithospheric Coupling Model. 1: Observations during the 5 August 2018 Bayan Earthquake". Remote Sensing 12, n. 20 (11 ottobre 2020): 3299. http://dx.doi.org/10.3390/rs12203299.
Testo completoAbstract (sommario):
The short-term prediction of earthquakes is an essential issue connected with human life protection and related social and economic matters. Recent papers have provided some evidence of the link between the lithosphere, lower atmosphere, and ionosphere, even though with marginal statistical evidence. The basic coupling is hypothesized as being via the atmospheric gravity wave (AGW)/acoustic wave (AW) channel. In this paper we analyze a scenario of the low latitude earthquake (Mw = 6.9) which occurred in Indonesia on 5 August 2018, through a multi-instrumental approach, using ground and satellites high quality data. As a result, we derive a new analytical lithospheric–atmospheric–ionospheric–magnetospheric coupling model with the aim to provide quantitative indicators to interpret the observations around 6 h before and at the moment of the earthquake occurrence.
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Turney, Chris S. M., Christopher J. Fogwill, Jonathan G. Palmer, Erik van Sebille, Zoë Thomas, Matt McGlone, Sarah Richardson et al. "Tropical forcing of increased Southern Ocean climate variability revealed by a 140-year subantarctic temperature reconstruction". Climate of the Past 13, n. 3 (15 marzo 2017): 231–48. http://dx.doi.org/10.5194/cp-13-231-2017.
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Abstract. Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine–atmosphere–ice domains interact on multi-decadal timescales and the impact of anthropogenic forcing. Here we integrate climate-sensitive tree growth with ocean and atmospheric observations on southwest Pacific subantarctic islands that lie at the boundary of polar and subtropical climates (52–54° S). Our annually resolved temperature reconstruction captures regional change since the 1870s and demonstrates a significant increase in variability from the 1940s, a phenomenon predating the observational record. Climate reanalysis and modelling show a parallel change in tropical Pacific sea surface temperatures that generate an atmospheric Rossby wave train which propagates across a large part of the Southern Hemisphere during the austral spring and summer. Our results suggest that modern observed high interannual variability was established across the mid-twentieth century, and that the influence of contemporary equatorial Pacific temperatures may now be a permanent feature across the mid- to high latitudes.
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Allan, Robert J., Joëlle Gergis e Rosanne D. D’Arrigo. "Placing the AD 2014–2016 ‘protracted’ El Niño episode into a long-term context". Holocene 30, n. 1 (19 settembre 2019): 90–105. http://dx.doi.org/10.1177/0959683619875788.
Testo completoAbstract (sommario):
Although extended or ‘protracted’ El Niño and La Niña episodes were first suggested nearly 20 years ago, they have not received the attention of other ‘flavours’ of the El Niño–Southern Oscillation (ENSO) or low-frequency ‘ENSO-like’ phenomena. In this study, instrumental variables and palaeoclimatic reconstructions are used to investigate the most recent ‘protracted’ El Niño episode in 2014–2016, and place it into a longer historical context. Although just reaching the threshold for such an episode, the 2014–2016 ‘protracted’ El Niño had very severe societal, agricultural, environmental and ecological impacts, particularly in western Pacific regions like eastern Australia. We show that although ‘protracted’ ENSO episodes of either phase cause similar, near-global modulations of weather and climate as during more ‘classical’ events, impacts associated with ‘protracted’ episodes last longer, with strong influences in eastern Australia. The latter is a response to the dominance of Niño 4 sea surface temperature (SST) and associated atmospheric teleconnection anomalies during ‘protracted’ ENSO episodes. Importantly, while Niño 4 SST anomalies recorded during the austral summer of 2016 were the highest values on record, an analysis of long-term palaeoclimate records indicates that there may have been episodes of greater magnitude and duration than seen in instrumental observations. This suggests that shorter instrumental observations may underestimate the risks of possible future ENSO extremes compared with those observed from multi-century palaeoclimate records. Improved knowledge of ENSO and the potential to forecast ‘protracted’ episodes would be of immense practical benefit to communities affected by the severe impacts of ENSO extremes.
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González-Gaitán, S., A. M. Mourão, F. Patat, J. P. Anderson, A. Cikota, K. Wiersema, A. B. Higgins e K. Silva. "Tips and tricks in linear imaging polarimetry of extended sources with FORS2 at the VLT". Astronomy & Astrophysics 634 (febbraio 2020): A70. http://dx.doi.org/10.1051/0004-6361/201936379.
Testo completoAbstract (sommario):
Context. Polarimetry is a very powerful tool for uncovering various properties of astronomical objects that otherwise remain hidden in standard imaging or spectroscopic observations. While common observations only measure the intensity of light, polarimetric measurements allow us to distinguish and measure the two perpendicular components of the electric field associated with the incoming light. By using polarimetry it is possible to unveil asymmetries in supernova explosions, properties of intervening dust, characteristics of atmosphere of planets, among others. However, the reliable measurement of the low polarization signal from astronomical sources requires a good control of spurious instrumental polarization induced by the various components of the optical system and the detector. Aims. We perform a detailed multi-wavelength calibration study of the FORS2 instrument at the VLT operating in imaging polarimetric mode to characterize the spatial instrumental polarization that may affect the study of extended sources. Methods. We used imaging polarimetry of high signal-to-noise ratio blank field BVRI observations during the full moon, when the polarization is expected to be constant across the field of view and deviations originate from the instrument, and a crowded star cluster in broad-band RI and narrow-band Hα filters, where the individual polarization values of each star across the field can be measured. Results. We find an instrumental polarization pattern that increases radially outwards from the optical axis of the instrument reaching up to 1.4% at the edges, depending on the filter. Our results are closely approximated by an elliptical paraboloid down to less than ∼0.05% accuracy, and ∼0.02% when using non-analytic fits. We present 2D maps to correct for this spurious instrumental polarization. We also give several tips and tricks for analyzing polarimetric measurements of extended sources. Conclusions. FORS2 is a powerful instrument that allows the linear polarimetry of extended sources to be mapped. We present and discuss a methodology that can be used to measure the polarization of such sources, and to correct for the spatial polarization induced in the optical system. This methodology could be applied to polarimetric measurements using other dual-beam polarimeters.
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Séran, E., M. Godefroy, K. Kauristie, J. C. Cerisier, J. J. Berthelier, M. Lester e L. E. Sarri. "What can we learn from HF signal scattered from a discrete arc?" Annales Geophysicae 27, n. 5 (4 maggio 2009): 1887–96. http://dx.doi.org/10.5194/angeo-27-1887-2009.
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Abstract. We present observations of a discrete southward propagating arc which appeared in the mid-night sector at latitudes equatorward of main substorm activity. The arc observations were made simultaneously by the ALFA (Auroral Light Fine Analysis) optical camera, the SuperDARN-CUTLASS HF radar and the Demeter satellite during a coordinated multi-instrumental campaign conducted at the KEOPS/ESRANGE site in December 2006. The SuperDARN HF signal which is often lost in the regions of strong electron precipitation yields in our case clear backscatter from an isolated arc of weak intensity. Consequently we are able to study arc dynamics, the formation of meso-scale irregularities of the electron density along the arc, compare the arc motion with the convection of surrounding plasma and discuss the contribution of ionospheric ions in the arc erosion and its propagation.
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Xu, J., F. Schreier, P. Vogt, A. Doicu e T. Trautmann. "A sensitivity study for far infrared balloon-borne limb emission sounding of stratospheric trace gases". Geoscientific Instrumentation, Methods and Data Systems Discussions 3, n. 1 (14 maggio 2013): 251–303. http://dx.doi.org/10.5194/gid-3-251-2013.
Testo completoAbstract (sommario):
Abstract. This paper presents a sensitivity study performed for trace gases retrieval from synthetic observations by TELIS (TErahertz and submillimeter LImb Sounder) which is a stratospheric balloon-borne cryogenic heterodyne spectrometer. Issues pertaining to hydroxyl radical (OH) retrieval from the far infrared measurements by the 1.8 THz channel are addressed. The study is conducted by a retrieval code PILS (Profile Inversion for Limb Sounding) developed to solve the nonlinear inverse problems arising in the analysis of infrared/microwave limb sounding measurements. PILS combines a line-by-line forward model with automatic differentiation for computing Jacobians and employs regularized nonlinear least squares inversion. We examine the application of direct and iterative regularization methods and evaluate the performance of single- and multi-profile retrievals. Sensitivities to expected errors in calibration procedure, instrumental knowledge and atmospheric profiles have been analyzed. Nonlinearity effect, inaccurate sideband ratio, and pointing error turned out to be the dominant error sources. Furthermore, the capability of multi-channel simultaneous retrieval from the far infrared and submillimeter data has been investigated. The errors and averaging kernels infer that the quality of the obtained hydrogen chloride (HCl) can be improved by significantly better exploitation of information from the observations.
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Rottmann, H., K. H. Mack, U. Klein, R. Wielebinski, N. Kassim e R. Perley. "The Radio Lobes of Virgo A". Symposium - International Astronomical Union 175 (1996): 343–44. http://dx.doi.org/10.1017/s0074180900081031.
Testo completoAbstract (sommario):
In the framework of our multi-frequency study of Virgo A we have performed observations of Vir A at 10.55 GHz with the Effelsberg 100-m telescope. Using our improved CLEAN procedure for single dish data we have increased the dynamic range to some 40 dB.By applying our newly developed polarization CLEANing technique we are able to diminish instrumental polarization effects. Since Faraday rotation is negligible at λ2.8 cm the measured linear polarization is a direct trace of the projected magnetic field in Vir A. In combination with low-frequency data obtained with the VLA it is possible to determine parameters like spectral indices, break frequencies, and spectral ages.
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García, Omaira E., Matthias Schneider, Eliezer Sepúlveda, Frank Hase, Thomas Blumenstock, Emilio Cuevas, Ramón Ramos et al. "Twenty years of ground-based NDACC FTIR spectrometry at Izaña Observatory – overview and long-term comparison to other techniques". Atmospheric Chemistry and Physics 21, n. 20 (18 ottobre 2021): 15519–54. http://dx.doi.org/10.5194/acp-21-15519-2021.
Testo completoAbstract (sommario):
Abstract. High-resolution Fourier transform infrared (FTIR) solar observations are particularly relevant for climate studies, as they allow atmospheric gaseous composition and multiple climate processes to be monitored in detail. In this context, the present paper provides an overview of 20 years of FTIR measurements taken in the framework of the NDACC (Network for the Detection of Atmospheric Composition Change) from 1999 to 2018 at the subtropical Izaña Observatory (IZO, Spain). Firstly, long-term instrumental performance is comprehensively assessed, corroborating the temporal stability and reliable instrumental characterization of the two FTIR spectrometers installed at IZO since 1999. Then, the time series of all trace gases contributing to NDACC at IZO are presented (i.e. C2H6, CH4, ClONO2, CO, HCl, HCN, H2CO, HF, HNO3, N2O, NO2, NO, O3, carbonyl sulfide (OCS), and water vapour isotopologues H216O, H218O, and HD16O), reviewing the major accomplishments drawn from these observations. In order to examine the quality and long-term consistency of the IZO FTIR observations, a comparison of those NDACC products for which other high-quality measurement techniques are available at IZO has been performed (i.e. CH4, CO, H2O, NO2, N2O, and O3). This quality assessment was carried out on different timescales to examine what temporal signals are captured by the FTIR records, and to what extent. After 20 years of operation, the IZO NDACC FTIR observations have been found to be very consistent and reliable over time, demonstrating great potential for climate research. Long-term NDACC FTIR data sets, such as IZO, are indispensable tools for the investigation of atmospheric composition trends, multi-year phenomena, and complex climate feedback processes, as well as for the validation of past and present space-based missions and chemistry climate models.
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Andrén, Henrik, Ilia Rodushkin, Anna Stenberg, Dmitry Malinovsky e Douglas C. Baxter. "Sources of mass bias and isotope ratio variation in multi-collector ICP-MS: optimization of instrumental parameters based on experimental observations". J. Anal. At. Spectrom. 19, n. 9 (2004): 1217–24. http://dx.doi.org/10.1039/b403938f.
Testo completo
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Petit, P., C. P. Folsom, J. F. Donati, L. Yu, J. D. do Nascimento, S. V. Jeffers, S. C. Marsden, J. Morin e A. A. Vidotto. "Multi-instrumental view of magnetic fields and activity of ϵ Eridani with SPIRou, NARVAL, and TESS". Astronomy & Astrophysics 648 (aprile 2021): A55. http://dx.doi.org/10.1051/0004-6361/202040027.
Testo completoAbstract (sommario):
Aims. We report on observations of the active K2 dwarf ϵ Eridani based on contemporaneous SPIRou, NARVAL and TESS data obtained over two months in late 2018, when the activity of the star was reported to be in a non-cyclic phase. Methods. Near-infrared (NIR) spectropolarimetry was obtained using SPIRou over four nights in late September, while visible spectropolarimetry was collected with NARVAL over 20 nights, spread between 18 September and 07 November. We first recovered the fundamental parameters of the target from both visible and NIR spectral fitting. The large-scale magnetic field was investigated from polarimetric data. From unpolarized spectra, we estimated the total magnetic flux through Zeeman broadening of magnetically sensitive NIR lines and the chromospheric emission using the CaII H&K lines. The photometric monitoring, secured with TESS between 19 October and 15 November, is modelled with pseudo-periodic Gaussian process regression. Results. Fundamental parameters of ϵ Eridani derived from visible and NIR wavelengths provide us with consistent results, which also agree with published values. We report a progressive increase of macroturbulence towards larger NIR wavelengths. Zeeman broadening of individual lines highlights an unsigned surface magnetic field Bmono = 1.90 ± 0.13 kG, with a filling factor f = 12.5 ± 1.7% (unsigned magnetic flux Bf = 237 ± 36 G). The large-scale magnetic field geometry, chromospheric emission and broadband photometry display clear signs of non-rotational evolution over the course of data collection. Characteristic decay times deduced from the light curve and longitudinal field fall in the range 30–40 days, while the characteristic timescale of surface differential rotation, as derived through the evolution of the magnetic geometry, is equal to 57 ± 5 days. The large-scale magnetic field exhibits a combination of properties not observed previously for ϵ Eridani, with a surface field among the weakest previously reported, but this field is also mostly axisymmetric, and is dominated by a toroidal component.
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Azzoni, S., D. Alonso, M. H. Abitbol, J. Errard e N. Krachmalnicoff. "A hybrid map-Cℓ component separation method for primordial CMB B-mode searches". Journal of Cosmology and Astroparticle Physics 2023, n. 03 (1 marzo 2023): 035. http://dx.doi.org/10.1088/1475-7516/2023/03/035.
Testo completoAbstract (sommario):
Abstract The observation of the polarised emission from the Cosmic Microwave Background (CMB) from future ground-based and satellite-borne experiments holds the promise of indirectly detecting the elusive signal from primordial tensor fluctuations in the form of large-scale B-mode polarisation. Doing so, however, requires an accurate and robust separation of the signal from polarised Galactic foregrounds. We present a component separation method for multi-frequency CMB observations that combines some of the advantages of map-based and power-spectrum-based techniques, and which is direcly applicable to data in the presence of realistic foregrounds and instrumental noise. We demonstrate that the method is able to reduce the contamination from Galactic foregrounds below an equivalent tensor-to-scalar ratio r FG ≲ 5 × 10-4, as required for next-generation observatories, for a wide range of foreground models with varying degrees of complexity. This bias reduction is associated with a mild ∼20–30% increase in the final statistical uncertainties, and holds for large sky areas, and for experiments targeting both the reionisation and recombination bumps in the B-mode power spectrum.
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Dinelli, B. M., E. Arnone, G. Brizzi, M. Carlotti, E. Castelli, L. Magnani, E. Papandrea, M. Prevedelli e M. Ridolfi. "The MIPAS2D database of MIPAS/ENVISAT measurements retrieved with a multi-target 2-dimensional tomographic approach". Atmospheric Measurement Techniques Discussions 2, n. 5 (16 ottobre 2009): 2639–88. http://dx.doi.org/10.5194/amtd-2-2639-2009.
Testo completoAbstract (sommario):
Abstract. We present a multi-year database of atmospheric state parameters retrieved for the upper tropospheric to mesospheric region from satellite measurements with a 2-dimensional tomographic approach. The full mission of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, on board the European Space Agency ENVISAT satellite, is analyzed with the Geofit Multi-Target Retrieval (GMTR) system to obtain the MIPAS2D database with atmospheric fields of pressure, temperature and volume mixing ratio of MIPAS main targets H2O, O3, HNO3, CH4, N2O, and NO2. The database covers both the MIPAS nominal observation mode measured at Full Resolution (FR) from July 2002 to March 2004 and the nominal observation mode of the new configuration, measured at Optimized Resolution (OR) and introduced in 2005. Further to the main targets, minor species N2O5, ClONO2, COF2, CFC-11, and CFC-12 for the FR mission only have been included in MIPAS2D to enhance its applicability in studies of stratospheric chemistry. The database is continuously updated with the analysis of the ongoing measurements that are planned to last until the end of 2013. The GMTR algorithm is operated on a fixed vertical grid coincident with the tangent altitudes of the FR nominal mode, spanning the altitude range from 6 to 68 km. In the horizontal domain, FR measurements are retrieved on both the observational grid and an equispaced 5 latitudinal-degrees grid which is made possible by the 2-dimensional retrieval algorithm. The analysis of MIPAS OR observations is operated on the same altitude-latitude fixed retrieval grid used for the FR measurements. This choice provides a homogeneous database in altitude and latitude, over the whole globe, covering to date about seven years of measurements. The equispaced latitudinal grid provides a new and convenient layout for the much needed synergetic studies of data from various instrumental and modeling sources. MIPAS2D is available to the scientific community through the two web sites http://www.mbf.fci.unibo.it/mipas2d.html, and http://www.isac.cnr.it/~rss/mipas2d.htm.
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Dinelli, B. M., E. Arnone, G. Brizzi, M. Carlotti, E. Castelli, L. Magnani, E. Papandrea, M. Prevedelli e M. Ridolfi. "The MIPAS2D database of MIPAS/ENVISAT measurements retrieved with a multi-target 2-dimensional tomographic approach". Atmospheric Measurement Techniques 3, n. 2 (17 marzo 2010): 355–74. http://dx.doi.org/10.5194/amt-3-355-2010.
Testo completoAbstract (sommario):
Abstract. We present a multi-year database of atmospheric fields of the upper troposphere, stratosphere and lower mesosphere retrieved from satellite measurements adopting a 2-dimensional tomographic approach. The full mission of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, on board the European Space Agency ENVISAT satellite, is analyzed with the Geofit Multi-Target Retrieval (GMTR) system to obtain the MIPAS2D database with atmospheric fields of pressure, temperature and volume mixing ratio of MIPAS main targets H2O, O3, HNO3, CH4, N2O, and NO2. The database covers both the MIPAS nominal observation mode measured at Full Resolution (FR) from July 2002 to March 2004 and the nominal observation mode of the new configuration, measured at Optimized Resolution (OR) and introduced in 2005. Further to the main targets, minor species N2O5, ClONO2, COF2, CFC-11, and CFC-12 for the FR mission only have been included in MIPAS2D to enhance its applicability in studies of stratospheric chemistry. The database is continuously updated with the analysis of the ongoing measurements that are planned to last until the end of 2013 and extended to other targets. The GMTR algorithm is operated on a fixed vertical grid coincident with the tangent altitudes of the FR nominal mode, spanning the altitude range from 6 to 68 km. In the horizontal domain, FR measurements are retrieved on both the observational grid and an equispaced 5 latitudinal-degrees grid which is made possible by the 2-dimensional retrieval algorithm. The analysis of MIPAS OR observations is operated on the same altitude-latitude fixed retrieval grid used for the FR measurements. This choice provides a database with a homogeneous altitude and latitude grid, over the whole globe, covering to date about seven years of measurements. The equispaced latitude grid provides a new and convenient layout for the much needed synergetic studies of data from various instrumental and modeling sources. MIPAS2D is available to the scientific community through the two web sites http://www.mbf.fci.unibo.it/mipas2d.html, and http://www.isac.cnr.it/~rss/mipas2d.htm
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Zhelezova, S. V. "Horse chestnut foliar dechromation instrumental monitoring damaged by Cameraria ohridella". FORESTRY BULLETIN 27, n. 5 (ottobre 2023): 138–48. http://dx.doi.org/10.18698/2542-1468-2023-5-138-148.
Testo completoAbstract (sommario):
A comparison of the visual and instrumental assessments of the horse chestnut foliar dechromation degree infested by the Ohrid miner (Cameraria ohridella) was carried out. The data of surveys of model trees for the period 2014–2022 in the Moscow region are compared. A statistically reliable regression relationship between the results of visual and instrumental assessment of dechromation in a long-term series of observations is shown. Instrumental monitoring of the leaves damages during the growing season was carried out based on the assessment of the NDVI vegetation index using the GreenSeeker Handheld® (Trimble) device. The seasonal dynamics of the NDVI index of foliage under Ohrid miner damage is presented on the example of the 2021 season. It is shown that the plants affected by the pest have a shorter growing season, and the average NDVI index for the season is 25...30 % lower than that of undamaged plants. In a nine-year series of observations, it was found that the transition of the NDVI index over the threshold value of 0.4 in plants affected by the Ohrid miner is observed on average 30...40 days earlier than in healthy plants. The possibility of assessing foliage dechromation based on the results of hyperspectral imaging without visualization using the Ocean Insight «Flame» spectrometer is considered. It is shown that the spectral characteristics of the reflectivity of healthy and damaged Ohrid miner leaves differ significantly, which was demonstrated by comparing the spectral brightness curves of reflection. Characteristic spectral zones in the visible and near infrared ranges have been identified, according to which the presence of leaf damage by a miner is successfully identified. It was found that in the near-infrared radiation area, the reflection of damaged leaves are significantly lower than that of healthy leaves, which indicates a decrease in the overall water content of chestnut leaf blades when damaged by pests. According to the results of multi- and hyperspectral surveys, it is possible to automatically determine the lesion of the horse chestnut foliage by the leaf-mining pest Cameraria ohridella.
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Treuhaft, R. N. "Astrometry in Local Reference Frames for Deep Space Navigation". Symposium - International Astronomical Union 129 (1988): 333–34. http://dx.doi.org/10.1017/s0074180900134904.
Testo completoAbstract (sommario):
Future deep space missions will benefit from submilliarcsecond angular navigation accuracy (< 25 km projected distance at Neptune). Conventional Very Long Baseline Interferometry (VLBI) measurement strategies entail observations of a radio source (RS) and spacecraft pair. To increase the 3–5 milliarcsecond accuracies currently attainable, instrumental improvements could be coupled with either of two methods: 1) Use improved calibration measurements with the single RS as the spacecraft reference, or 2) use a reference frame established by a local network of RS's near the spacecraft to reduce the contribution of sky-dependent error sources. The demanding baseline vector (earth orientation) and tropospheric calibrations needed to realize submilliarcsecond accuracy with the single-source strategy would not be necessary with the multi-source strategy. The two strategies are compared via a sample covariance analysis. In this analysis, the single-source method yields 1.5 milliarcseconds for the navigation accuracy, while the multi-source method yields 0.5 milliarcseconds.
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Xu, Feng, David Diner, Oleg Dubovik e Yoav Schechner. "A Correlated Multi-Pixel Inversion Approach for Aerosol Remote Sensing". Remote Sensing 11, n. 7 (27 marzo 2019): 746. http://dx.doi.org/10.3390/rs11070746.
Testo completoAbstract (sommario):
Aerosol retrieval algorithms used in conjunction with remote sensing are subject to ill-posedness. To mitigate non-uniqueness, extra constraints (in addition to observations) are valuable for stabilizing the inversion process. This paper focuses on the imposition of an empirical correlation constraint on the retrieved aerosol parameters. This constraint reflects the empirical dependency between different aerosol parameters, thereby reducing the number of degrees of freedom and enabling accelerated computation of the radiation fields associated with neighboring pixels. A cross-pixel constraint that capitalizes on the smooth spatial variations of aerosol properties was built into the original multi-pixel inversion approach. Here, the spatial smoothness condition is imposed on principal components (PCs) of the aerosol model, and on the corresponding PC weights, where the PCs are used to characterize departures from the mean. Mutual orthogonality and unit length of the PC vectors, as well as zero sum of the PC weights also impose stabilizing constraints on the retrieval. Capitalizing on the dependencies among aerosol parameters and the mutual orthogonality of PCs, a perturbation-based radiative transfer computation scheme is developed. It uses a few dominant PCs to capture the difference in the radiation fields across an imaged area. The approach is tested using 27 observations acquired by the Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) during multiple NASA field campaigns and validated using collocated AERONET observations. In particular, aerosol optical depth, single scattering albedo, aerosol size, and refractive index are compared with AERONET aerosol reference data. Retrieval uncertainty is formulated by accounting for both instrumental errors and the effects of multiple types of constraints.
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Bencherif, Hassan, Nelson Bègue, Damaris Kirsch Pinheiro, David Jean du Preez, Jean-Maurice Cadet, Fábio Juliano da Silva Lopes, Lerato Shikwambana et al. "Investigating the Long-Range Transport of Aerosol Plumes Following the Amazon Fires (August 2019): A Multi-Instrumental Approach from Ground-Based and Satellite Observations". Remote Sensing 12, n. 22 (23 novembre 2020): 3846. http://dx.doi.org/10.3390/rs12223846.
Testo completoAbstract (sommario):
Despite a number of studies on biomass burning (BB) emissions in the atmosphere, observation of the associated aerosols and pollutants requires continuous efforts. Brazil, and more broadly Latin America, is one of the most important seasonal sources of BB, particularly in the Amazon region. Uncertainty about aerosol loading in the source regions is a limiting factor in terms of understanding the role of aerosols in climate modelling. In the present work, we investigated the Amazon BB episode that occurred during August 2019 and made the international headlines, especially when the smoke plumes plunged distant cities such as São Paulo into darkness. Here, we used satellite and ground-based observations at different locations to investigate the long-range transport of aerosol plumes generated by the Amazon fires during the study period. The monitoring of BB activity was carried out using fire related pixel count from the moderate resolution imaging spectroradiometer (MODIS) onboard the Aqua and Terra platforms, while the distribution of carbon monoxide (CO) concentrations and total columns were obtained from the infrared atmospheric sounding interferometer (IASI) onboard the METOP-A and METOP-B satellites. In addition, AERONET sun-photometers as well as the MODIS instrument made aerosol optical depth (AOD) measurements over the study region. Our datasets are consistent with each other and highlight AOD and CO variations and long-range transport of the fire plume from the source regions in the Amazon basin. We used the Lagrangian transport model FLEXPART (FLEXible PARTicle) to simulate backward dispersion, which showed good agreement with satellite and ground measurements observed over the study area. The increase in Rossby wave activity during the 2019 austral winter the Southern Hemisphere may have contributed to increasing the efficiency of large-scale transport of aerosol plumes generated by the Amazon fires during the study period.
36
Samadi, R., A. Deru, D. Reese, V. Marchiori, E. Grolleau, J. J. Green, M. Pertenais et al. "The PLATO Solar-like Light-curve Simulator". Astronomy & Astrophysics 624 (aprile 2019): A117. http://dx.doi.org/10.1051/0004-6361/201834822.
Testo completoAbstract (sommario):
Context. ESA’s PLATO space mission, to be launched by the end of 2026, aims to detect and characterise Earth-like planets in their habitable zone using asteroseismology and the analysis of the transit events. The preparation of science objectives will require the implementation of hare-and-hound exercises relying on the massive generation of representative simulated light-curves. Aims. We developed a light-curve simulator named the PLATO Solar-like Light-curve Simulator (PSLS) in order to generate light-curves representative of typical PLATO targets, that is showing simultaneously solar-like oscillations, stellar granulation, and magnetic activity. At the same time, PSLS also aims at mimicking in a realistic way the random noise and the systematic errors representative of the PLATO multi-telescope concept. Methods. To quantify the instrumental systematic errors, we performed a series of simulations at pixel level that include various relevant sources of perturbations expected for PLATO. From the simulated pixels, we extract the photometry as planned on-board and also simulate the quasi-regular updates of the aperture masks during the observations. The simulated light-curves are then corrected for instrumental effects using the instrument point spread functions reconstructed on the basis of a microscanning technique that will be operated during the in-flight calibration phases of the mission. These corrected and simulated light-curves are then fitted by a parametric model, which we incorporated in PSLS. Simulation of the oscillations and granulation signals rely on current state-of-the-art stellar seismology. Results. We show that the instrumental systematic errors dominate the signal only at frequencies below ∼20 μHz. The systematic errors level is found to mainly depend on stellar magnitude and on the detector charge transfer inefficiency. To illustrate how realistic our simulator is, we compared its predictions with observations made by Kepler on three typical targets and found a good qualitative agreement with the observations. Conclusions. PSLS reproduces the main properties of expected PLATO light-curves. Its speed of execution and its inclusion of relevant stellar signals as well as sources of noises representative of the PLATO cameras make it an indispensable tool for the scientific preparation of the PLATO mission.
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Lupsic, Balazs, e Bence Takacs. "Gauss process regression for real-time ionospheric delay estimation from GNSS observations". Acta Geodaetica et Geophysica 57, n. 1 (12 gennaio 2022): 107–27. http://dx.doi.org/10.1007/s40328-021-00368-y.
Testo completoAbstract (sommario):
AbstractThe number of devices equipped with global satellite positioning has exceeded seven billion recently. There are a wide variety of receivers regarding their accuracy and reliability. Low cost, multi-frequency units have been released on the market latterly; however, the number of single-frequency receivers is still significant. Since their measurements are influenced by ionospheric delay, accurate ionosphere models are of utmost importance to reduce the effect. This paper summarizes how Gauss process regression (GPR) can be applied to derive near real-time regional ionosphere models using raw Global Navigation Satellite System (GNSS) observations of permanent stations. While Gauss process is widely used in machine learning, GPR is a nonparametric, Bayesian approach to regression. GPR has several benefits for ionosphere monitoring since it is quite robust and efficient to derive a grid model from data available in irregular set of ionospheric pierce points. The corresponding instrumental delays are estimated by a parallel Kalman filter. The presented algorithm can be applied near real-time, however the results are offline calculated and are compared to two high quality TEC map products. Based on the analysis, the accuracy of the GPR modell is in 2 TECu range. The developed methods could be efficiently applied in the field of autonomous vehicle navigation with meeting both accuracy and integrity requirements.
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Calvello, Mariarosaria, Rosa Caggiano, Francesco Esposito, Antonio Lettino, Serena Sabia, Vito Summa e Giulia Pavese. "IMAA (Integrated Measurements of Aerosol in Agri valley) campaign: Multi-instrumental observations at the largest European oil/gas pre-treatment plant area". Atmospheric Environment 169 (novembre 2017): 297–306. http://dx.doi.org/10.1016/j.atmosenv.2017.09.026.
Testo completo
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Bittencourt, Gabriela Dornelles, Hassan Bencherif, Damaris Kirsch Pinheiro, Nelson Begue, Lucas Vaz Peres, José Valentin Bageston, Douglas Lima de Bem, Francisco Raimundo da Silva e Tristan Millet. "Multi-instrumental analysis of ozone vertical profiles and total columns in South America: comparison between subtropical and equatorial latitudes". Atmospheric Measurement Techniques 17, n. 17 (6 settembre 2024): 5201–20. http://dx.doi.org/10.5194/amt-17-5201-2024.
Testo completoAbstract (sommario):
Abstract. The behavior of ozone gas (O3) in the atmosphere varies according to the region of the globe. Its formation occurs mainly in the tropical stratosphere through the photodissociation of molecular oxygen with the aid of the incidence of ultraviolet solar radiation. Still, the highest concentrations of O3 content are found in high-latitude regions (poles) due to the Brewer–Dobson circulation, a large-scale circulation that takes place from the tropics to the pole in the winter hemisphere. This work presents a multi-instrumental analysis at two Brazilian sites, a subtropical one (Santa Maria – 29.72° S, 53.41° W) and an equatorial one (Natal – 5.4° S, 35.4° W), to investigate ozone distributions in terms of vertical profiles (2002–2020) and total abundance in terms of total columns of ozone (1979–2020). The study is based on the use of ground-based and satellite observations. Ozone profiles over Natal, from the ground up to the mesosphere, are obtained by radiosonde experiments (0–30 km) in the framework of the SHADOZ program and by satellite measurements from the SABER instrument (15–60 km). This enabled the construction of a continuous time series for ozone, including monthly values and climatological trends. There is a good agreement between the two measurements in the common observation layer, mainly for altitudes above 20 km. Below 20 km, SABER ozone profiles showed high variability and overestimated ozone mixing ratios by over 50 %. Dynamic and photochemical effects can interfere with O3 formation and distribution along higher latitudes through the Brewer–Dobson circulation. The measurements of the total ozone columns used are in good agreement with each other (TOMS/OMI × Dobson for Natal and TOMS/OMI × Brewer for Santa Maria) in time and space, in line with previous studies for these latitudes. Wavelet analysis was used over 42 years. The investigation revealed a significant annual cycle in both data series for both sites. The study highlighted that the quasi-biennial oscillation (QBO) plays a significant role in the variability of stratospheric ozone at the two study sites – Natal and Santa Maria. The QBO's contribution was found to be stronger at the Equator (Natal) than at the subtropics (Santa Maria). Additionally, the study showed that the 11-year solar cycle also has a significant impact on ozone variability at both locations. Given the study latitudes, the ozone variations observed at the two sites showed different patterns and amounts. Only a limited number of studies have been conducted on stratospheric ozone in South America, particularly in the region between the Equator and the subtropics. The primary aim of this work is to investigate the behavior of stratospheric ozone at various altitudes and latitudes using ground-based and satellite measurements in terms of vertical profiles and total columns of ozone.
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Bourdin, H., A. S. Baldi, A. Kozmanyan e P. Mazzotta. "Extracting the thermal SZ signal from heterogeneous millimeter data sets". EPJ Web of Conferences 228 (2020): 00007. http://dx.doi.org/10.1051/epjconf/202022800007.
Testo completoAbstract (sommario):
Complementarily to X-ray observations, the thermal SZ effect is a powerful tool to probe the baryonic content of galaxy clusters from their core to their peripheries. While contaminations by astrophysical and instrumental backgrounds require us to scan the thermal SZ signal across various frequencies, the multi-scale nature of cluster morphologies require us to observe such objects at various angular resolutions. We developed component separation algorithms that take advantage of sparse representations to combine these heterogeneous pieces of information, separate the thermal SZ signal from its contaminants, detect and map the thermal SZ signal of galaxy clusters from nearby to more distant clusters of the Planck catalogue. Spatially weighted likelihoods allow us in particular to connect parametric fittings of the component Spectral Energy Distribution with wavelet and curvelet imaging, but also to combine signals registered with beams of various width. Such techniques already allow us to detect sub-structures in the peripheries of nearby clusters with Planck, and could be extended to observations performed at higher angular resolutions.
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Lu, Weijun, Guanyi Ma e Qingtao Wan. "A Review of Voxel-Based Computerized Ionospheric Tomography with GNSS Ground Receivers". Remote Sensing 13, n. 17 (29 agosto 2021): 3432. http://dx.doi.org/10.3390/rs13173432.
Testo completoAbstract (sommario):
Ionized by solar radiation, the ionosphere causes a phase rotation or time delay to trans-ionospheric radio waves. Reconstruction of ionospheric electron density profiles with global navigation satellite system (GNSS) observations has become an indispensable technique for various purposes ranging from space physics studies to radio applications. This paper conducts a comprehensive review on the development of voxel-based computerized ionospheric tomography (CIT) in the last 30 years. A brief introduction is given in chronological order starting from the first report of CIT with simulation to the newly proposed voxel-based algorithms for ionospheric event analysis. The statement of the tomographic geometry and voxel models are outlined with the ill-posed and ill-conditioned nature of CIT addressed. With the additional information from other instrumental observations or initial models supplemented to make the coefficient matrix less ill-conditioned, equation constructions are categorized into constraints, virtual data assimilation and multi-source observation fusion. Then, the paper classifies and assesses the voxel-based CIT algorithms of the algebraic method, statistical approach and artificial neural networks for equation solving or electron density estimation. The advantages and limitations of the algorithms are also pointed out. Moreover, the paper illustrates the representative height profiles and two-dimensional images of ionospheric electron densities from CIT. Ionospheric disturbances studied with CIT are presented. It also demonstrates how the CIT benefits ionospheric correction and ionospheric monitoring. Finally, some suggestions are provided for further research about voxel-based CIT.
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Chen, Hongyan, Qingdan Zeng e Zhengmei Peng. "Creating the Recognition of Heterogeneity in Circle Rituals: An Ethnographic Study in a German Primary School". SAGE Open 10, n. 1 (gennaio 2020): 215824401989944. http://dx.doi.org/10.1177/2158244019899440.
Testo completoAbstract (sommario):
This study focuses on “circle time,” an innovative technique to promote classroom organization in primary schools across Germany and the rest of the world. Unlike previous research which primarily emphasizes on the functional and instrumental dimensions of circle time, the current study examines the non-cognitive aspects that emerged “in the middle” of circles. Since 2013, an ethnographic study has been conducted in a progressive pedagogy (Reformpädagogik) primary school in Berlin, Germany. The empirical data from this study contain observations from the ethnographic videotaping of students aged 6 to 9 years old. The findings suggest that three aspects are crucial to generating and handling heterogeneity in a circle: symbolic construction, bodily movement, and ludic interaction. In addition, it is indicated that in a pluralistic, multi-cultural society, a teacher’s authority becomes conditional rather than automatic.
43
Egal, A., P. G. Brown, J. Rendtel, M. Campbell-Brown e P. Wiegert. "Activity of the Eta-Aquariid and Orionid meteor showers". Astronomy & Astrophysics 640 (agosto 2020): A58. http://dx.doi.org/10.1051/0004-6361/202038115.
Testo completoAbstract (sommario):
Aims. We present a multi-instrumental, multidecadal analysis of the activity of the Eta-Aquariid and Orionid meteor showers for the purpose of constraining models of 1P/Halley’s meteoroid streams. Methods. The interannual variability of the showers’ peak activity and period of duration is investigated through the compilation of published visual and radar observations prior to 1985 and more recent measurements reported in the International Meteor Organization (IMO) Visual Meteor DataBase, by the IMO Video Meteor Network and by the Canadian Meteor Orbit Radar (CMOR). These techniques probe the range of meteoroid masses from submilligrams to grams. The η-Aquariids and Orionids activity duration, shape, maximum zenithal hourly rates values, and the solar longitude of annual peaks since 1985 are analyzed. When available, annual activity profiles recorded by each detection network were measured and are compared. Results. Observations from the three detection methods show generally good agreement in the showers’ shape, activity levels, and annual intensity variations. Both showers display several activity peaks of variable location and strength with time. The η-Aquariids are usually two to three times stronger than the Orionids, but the two showers display occasional outbursts with peaks two to four times their usual activity level. CMOR observations since 2002 seem to support the existence of an ~12 yr cycle in Orionids activity variations; however, additional and longer term radar and optical observations of the shower are required to confirm such periodicity.
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Rizal, Januar. "Deradikalisasi dan Penanggulangan Terorisme di Indonesia: Telaah Paradigmatik Melalui Teori Rekognisi Axel Honneth". Jurnal Keamanan Nasional 7, n. 2 (20 gennaio 2022): 109–23. http://dx.doi.org/10.31599/jkn.v7i2.523.
Testo completoAbstract (sommario):
The development of policies to combat terrorism in Indonesia shows the relationship between counter-terrorism and de-radicalization activities against ex-convicts. Currently, a fundamental and philosophical study of deradicalization is still needed. The views of Dahrendorf's conflict theory, and Berger Luckmann's theory of social reality construction, are seen through a paradigmatic study of critical theory. Axel Honneth's recognition theory as the third generation critical theory of the Frankfurt school is used to analyze the phenomenon of deradicalization in countering terrorism in Indonesia. Through the qualitative research format of multi-case instrumental case studies with in-depth interviews and involved observations of ex-convicts who have been able to have social independence, this study finds an emancipatory dialectic space in the phenomenon of deradicalization in Indonesia. The emancipatory dialectic space became a “new engagement” for the phenomenon of deradicalization of the ex-napiters.
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Chernigovskaya, M. A., B. G. Shpynev, A. S. Yasyukevich, D. S. Khabituev, K. G. Ratovsky, A. Yu Belinskaya, A. E. Stepanov et al. "Longitudinal variations in the response of the mid-latitude ionosphere of the Northern Hemisphere to the October 2016 geomagnetic storm using multi-instrumental observations". Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa 18, n. 5 (2021): 305–17. http://dx.doi.org/10.21046/2070-7401-2021-18-5-305-317.
Testo completo
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Berrilli, Francesco, e Luca Giovannelli. "The Great Aurora of 4 February 1872 observed by Angelo Secchi in Rome". Journal of Space Weather and Space Climate 12 (2022): 3. http://dx.doi.org/10.1051/swsc/2021046.
Testo completoAbstract (sommario):
Observation of auroras at low latitudes is an extremely rare event typically associated with major magnetic storms due to intense Earth-directed Coronal Mass Ejections. Since these energetic events represent one of the most important components of space weather, their study is of paramount importance to understand the Sun-Earth connection. Due to the rarity of these events, being able to access all available information for the few cases studied is equally important. Especially if we refer to historical periods in which current accurate observations from ground-based instruments or space were not available. Certainly, among these events, we must include the great aurora of February 4, 1872. An event whose effects have been observed in different regions of the Earth. What we could consider today a global event, especially for its effects on the communication systems of the time, such as the transatlantic cable that allowed a connection between the United States and Europe since 1866. In this paper, we describe the main results of the observations and studies carried out by Angelo Secchi at the Observatory of the Roman College and described in his Memoria sull’Aurora Elettrica del 4 Febbraio 1872 for the Notes of the Pontifical Academy of new Lincei. This note is extremely modern both in its multi-instrumental approach to the study of these phenomena and in its association between solar-terrestrial connection and technological infrastructures on the Earth. The Secchi’s note definitely represents the first example of analysis and study of an event on a global scale, such as the Atlantic cable, affecting the Earth. What we nowadays call an extreme space weather event.
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Kalluri, Raja Obul Reddy, Balakrishnaiah Gugamsetty, Chakradhar Rao Tandule, Rama Gopal Kotalo, Lokeswara Reddy Thotli, Ramakrishna Reddy Rajuru e Surya Nagi Reddy Palle. "Impact of aerosols on surface ozone during COVID-19 pandemic in southern India: A multi-instrumental approach from ground and satellite observations, and model simulations". Journal of Atmospheric and Solar-Terrestrial Physics 212 (gennaio 2021): 105491. http://dx.doi.org/10.1016/j.jastp.2020.105491.
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Aa, Ercha, Shun-Rong Zhang, Philip J. Erickson, Wenbin Wang e Anthea J. Coster. "3-D Ionospheric Electron Density Variations during the 2017 Great American Solar Eclipse: A Revisit". Atmosphere 14, n. 9 (31 agosto 2023): 1379. http://dx.doi.org/10.3390/atmos14091379.
Testo completoAbstract (sommario):
This paper studies the three-dimensional (3-D) ionospheric electron density variation over the continental US and adjacent regions during the August 2017 Great American Solar Eclipse event, using Millstone Hill incoherent scatter radar observations, ionosonde data, the Swarm satellite measurements, and a new TEC-based ionospheric data assimilation system (TIDAS). The TIDAS data assimilation system can reconstruct a 3-D electron density distribution over continental US and adjacent regions, with a spatial–temporal resolution of 1∘× 1∘ in latitude and longitude, 20 km in altitude, and 5 min in universal time. The combination of multi-instrumental observations and the high-resolution TIDAS data assimilation products can well represent the dynamic 3-D ionospheric electron density response to the solar eclipse, providing important altitude information and fine-scale details. Results show that the eclipse-induced ionospheric electron density depletion can exceed 50% around the F2-layer peak height between 200 and 300 km. The recovery of electron density following the maximum depletion exhibits an altitude-dependent feature, with lower altitudes exhibiting a faster recovery than the F2 peak region and above. The recovery feature was also characterized by a post-eclipse electron density enhancement of 15–30%, which is particularly prominent in the topside ionosphere at altitudes above 300 km.
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Haqq-Misra, J., P. Applegate, B. Tuttle, R. Nicholas e K. Keller. "A computationally efficient model for the Greenland ice sheet". Cryosphere Discussions 6, n. 4 (23 luglio 2012): 2751–88. http://dx.doi.org/10.5194/tcd-6-2751-2012.
Testo completoAbstract (sommario):
Abstract. We present a one-dimensional model of the Greenland Ice Sheet (GIS) for use in analysis of future sea level rise. Simulations using complex three-dimensional models suggest that the GIS may respond in a nonlinear manner to anthropogenic climate forcing and cause potentially nontrivial sea level rise. These GIS projections are, however, deeply uncertain. Analyzing these uncertainties is complicated by the substantial computational demand of the current generation of complex three-dimensional GIS models. As a result, it is typically computationally infeasible to perform the large number of model evaluations required to carefully explore a multi-dimensional parameter space, to fuse models with observational constraints, or to assess risk-management strategies in Integrated Assessment Models (IAMs) of climate change. Here we introduce GLISTEN (GreenLand Ice Sheet ENhanced), a computationally efficient, mechanistically based, one-dimensional flow-line model of GIS mass balance capable of reproducing key instrumental and paleo-observations as well as emulating more complex models. GLISTEN is based on a simple model developed by Pattyn (2006). We have updated and extended this original model by improving its computational functionality and representation of physical processes such as precipitation, ablation, and basal sliding. The computational efficiency of GLISTEN enables a systematic and extensive analysis of the GIS behavior across a wide range of relevant parameters and can be used to represent a potential GIS threshold response in IAMs. We demonstrate the utility of GLISTEN by performing a pre-calibration and analysis. We find that the added representation of processes in GLISTEN, along with pre-calibration of the model, considerably improves the hindcast skill of paleo-observations.
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Simon, C., J. Lilensten, J. Moen, J. M. Holmes, Y. Ogawa, K. Oksavik e W. F. Denig. "TRANS4: a new coupled electron/proton transport code – comparison to observations above Svalbard using ESR, DMSP and optical measurements". Annales Geophysicae 25, n. 3 (29 marzo 2007): 661–73. http://dx.doi.org/10.5194/angeo-25-661-2007.
Testo completoAbstract (sommario):
Abstract. We present for the first time a numerical kinetic/fluid code for the ionosphere coupling proton and electron effects. It solves the fluid transport equations up to the eighth moment, and the kinetic equations for suprathermal particles. Its new feature is that for the latter, both electrons and protons are taken into account, while the preceding codes (TRANSCAR) only considered electrons. Thus it is now possible to compute in a single run the electron and ion densities due to proton precipitation. This code is successfully applied to a multi-instrumental data set recorded on 22 January 2004. We make use of measurements from the following set of instruments: the Defence Meteorological Satellite Program (DMSP) F-13 measures the precipitating particle fluxes, the EISCAT Svalbard Radar (ESR) measures the ionospheric parameters, the thermospheric oxygen lines are measured by an all-sky camera and the Hα line is given by an Ebert-Fastie spectrometer located at Ny-Ålesund. We show that the code computes the Hα spectral line profile with an excellent agreement with observations, providing some complementary information on the physical state of the atmosphere. We also show the relative effects of protons and electrons as to the electron densities. Computed electron densities are finally compared to the direct ESR measurements.