The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
G. Vaughan - One of the best experts on this subject based on the ideXlab platform.
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Latitudinal distribution of Stratospheric Aerosols during the EASOE winter 1991/92
Geophysical Research Letters, 1994Co-Authors: R. Neuber, Sophie Godin, Christine David, G. Beyerle, G. Fiocco, A. Di Sarra, K. Fricke, B. Knudsen, L. Stefanutti, G. VaughanAbstract:Lidar measurements of Stratospheric Aerosols were made at several Arctic and mid-latitude stations as part of the European Arctic Stratospheric Ozone Experiment (EASOE) in 1991/92. Volcanic Aerosols were observed throughout the winter at all stations. High latitude stations observed an aerosol-free stratosphere during most of the winter at altitudes above 450 K potential temperature (above 16 km). An even latitudinal distribution of volcanic Aerosols was observed below this level. This is interpreted as indicative of latitudinal transport into the polar region throughout the winter.
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latitudinal distribution of Stratospheric Aerosols during the easoe winter 1991 92
Geophysical Research Letters, 1994Co-Authors: R. Neuber, Sophie Godin, G. Beyerle, G. Fiocco, A. Di Sarra, L. Stefanutti, K H Fricke, Ch David, Bjorn M Knudsen, G. VaughanAbstract:This paper summarizes lidar measurements of Stratospheric Aerosols spanning the latitude range from 44[degrees]N to 79[degrees]N, during the period of the EASOE campaign. The Arctic region measurements show no aerosol content above roughly 16 km, but the density is fairly constant at lower altitudes independent of latitude. The authors argue this indicates latitudinal transport of aerosol throughout the winter.
Johann Feichter - One of the best experts on this subject based on the ideXlab platform.
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effects of Stratospheric sulfate aerosol geo engineering on cirrus clouds
Geophysical Research Letters, 2012Co-Authors: Miriam Kuebbeler, Ulrike Lohmann, Johann FeichterAbstract:[1] Cooling the Earth through the injection of sulphate into the stratosphere is one of the most discussed geo-engineering (GE) schemes. Stratospheric Aerosols can sediment into the troposphere, modify the aerosol composition and thus might impact cirrus clouds. We use a global climate model with a physically based parametrization for cirrus clouds in order to investigate possible microphysical and dynamical effects. We find that enhanced Stratospheric aerosol loadings as proposed by several GE approaches will likely lead to a reduced ice crystal nucleation rate and thus optically thinner cirrus clouds. These optically thinner cirrus clouds exert a strong negative cloud forcing in the long-wave which contributes by 60% to the overall net GE forcing. This shows that indirect effects of Stratospheric Aerosols on cirrus clouds may be important and need to be considered in order to estimate the maximum cooling derived from Stratospheric GE.
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Effects of Stratospheric sulfate aerosol geo‐engineering on cirrus clouds
Geophysical Research Letters, 2012Co-Authors: Miriam Kuebbeler, Ulrike Lohmann, Johann FeichterAbstract:[1] Cooling the Earth through the injection of sulphate into the stratosphere is one of the most discussed geo-engineering (GE) schemes. Stratospheric Aerosols can sediment into the troposphere, modify the aerosol composition and thus might impact cirrus clouds. We use a global climate model with a physically based parametrization for cirrus clouds in order to investigate possible microphysical and dynamical effects. We find that enhanced Stratospheric aerosol loadings as proposed by several GE approaches will likely lead to a reduced ice crystal nucleation rate and thus optically thinner cirrus clouds. These optically thinner cirrus clouds exert a strong negative cloud forcing in the long-wave which contributes by 60% to the overall net GE forcing. This shows that indirect effects of Stratospheric Aerosols on cirrus clouds may be important and need to be considered in order to estimate the maximum cooling derived from Stratospheric GE.
Filip Vanhellemont - One of the best experts on this subject based on the ideXlab platform.
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characterization of Stratospheric aerosol distribution for volcanic and non volcanic Aerosols observed through 16 years of sage ii data 1984 2000
Geophysical monograph, 2013Co-Authors: Christine Bingen, Didier Fussen, Filip VanhellemontAbstract:The particle number density and particle size distribution of Stratospheric Aerosols have been derived from aerosol extinction profiles provided by the Stratospheric Aerosol and Gas Experiment II (SAGE II), using a regularized optical inversion method. We present here a global climatology derived from those profiles, and describe the spatiotemporal evolution of Stratospheric Aerosols through the three following aerosol parameters: particle number density, modal radius and modal width of the size distribution that is supposed to be lognormal. We illustrate the evolution of all those parameters, especially in the case of high and very low volcanism. We put emphasis on the latter case, which already could be studied during previous periods of quiet volcanic activity. We present profiles of aerosol parameters that reflect a possible situation of background aerosol, and compare them with previously published works.
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optical extinction by upper tropospheric Stratospheric Aerosols and clouds gomos observations for the period 2002 2008
Atmospheric Chemistry and Physics, 2010Co-Authors: Filip Vanhellemont, Christine Bingen, Didier Fussen, Nina Mateshvili, Cédric Tétard, Emmanuel Dekemper, Nicolas Loodts, Erkki Kyrölä, Viktoria Sofieva, Johanna TamminenAbstract:Although the retrieval of aerosol extinction coefficients from satellite remote measurements is notoriously difficult (in comparison with gaseous species) due to the lack of typical spectral signatures, important information can be obtained. In this paper we present an overview of the current operational nighttime UV/Vis aerosol extinction profile results for the GOMOS star occultation instrument, spanning the period from August 2002 to May 2008. Some problems still remain, such as the ones associated with incomplete scintillation correction and the aerosol spectral law implementation, but good quality extinction values are obtained at a wavelength of 500 nm. Typical phenomena associated with atmospheric particulate matter in the Upper Troposphere/Lower Stratosphere (UTLS) are easily identified: Polar Stratospheric Clouds, tropical subvisual cirrus clouds, background Stratospheric Aerosols, and post-eruption volcanic Aerosols (with their subsequent dispersion around the globe). For the first time, we show comparisons of GOMOS 500 nm particle extinction profiles with the ones of other satellite occultation instruments (SAGE II, SAGE III and POAM III), of which the good agreement lends credibility to the GOMOS data set. Yearly zonal statistics are presented for the entire period considered. Time series furthermore convincingly show an important new finding: the sensitivity of GOMOS to the sulfate input by moderate volcanic eruptions such as Manam (2005) and Soufriere Hills (2006). Finally, PSCs are well observed by GOMOS and a first qualitative analysis of the data agrees well with the theoretical PSC formation temperature. Therefore, the importance of the GOMOS aerosol/cloud extinction profile data set is clear: a long-term data record of PSCs, subvisual cirrus, and background and volcanic Aerosols in the UTLS region, consisting of hundreds of thousands of altitude profiles with near-global coverage, with the potential to fill the aerosol/cloud extinction data gap left behind after the discontinuation of occultation instruments such as SAGE II, SAGE III and POAM III.
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Optical extinction by upper tropospheric/Stratospheric Aerosols and clouds: GOMOS observations for the period 2002-2008
Atmospheric Chemistry and Physics, 2010Co-Authors: Filip Vanhellemont, Christine Bingen, Didier Fussen, Nina Mateshvili, Cédric Tétard, Emmanuel Dekemper, Nicolas Loodts, Erkki Kyrölä, Viktoria Sofieva, Johanna TamminenAbstract:Although the retrieval of aerosol extinction coefficients from satellite remote measurements is notoriously difficult (in comparison with gaseous species) due to the lack of typical spectral signatures, important information can be obtained. In this paper we present an overview of the current operational nighttime UV/Vis aerosol extinction profile results for the GOMOS star occultation instrument, spanning the period from August 2002 to May 2008. Some problems still remain, such as the ones associated with incomplete scintillation correction and the aerosol spectral law implementation, but good quality extinction values can be expected at a wavelength of 500 nm. Typical phenomena associated with atmospheric particulate matter in the Upper Troposphere/Lower Stratosphere (UTLS) are easily identified: Polar Stratospheric Clouds, tropical subvisual cirrus clouds, background Stratospheric Aerosols, and post-eruption volcanic Aerosols (with their subsequent dispersion around the globe). In this overview paper we will give a summary of the current results.
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A review of Stratospheric aerosol characterization
Advances in Space Research, 2006Co-Authors: Christine Bingen, Didier Fussen, Filip VanhellemontAbstract:We present a general overview of the efforts devoted to the characterization of Stratospheric Aerosols. After recalling the most important parameters used to characterize Aerosols, we present an overview of methods used for retrieving these parameters from radiative measurements. We subsequently review the most important climatological studies developed to characterize Stratospheric Aerosols, and analyse the main contributions and limitations of these works. Finally, we try to identify current topics of interest and perspectives in the field of aerosol characterization.
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optical and physical properties of Stratospheric Aerosols from balloon measurements in the visible and near infrared domains iii presence of Aerosols in the middle stratosphere
Applied Optics, 2005Co-Authors: Jean-baptiste Renard, Didier Fussen, Filip Vanhellemont, Gwenael Berthet, Joëlle Ovarlez, Colette Brogniez, Edith Hadamcik, Michel Chartier, Henri OvarlezAbstract:The aerosol extinction measurements in the ultraviolet and visible wavelengths by the balloonborne spectrometer Spectroscopie d’Absorption Lunaire pour l’Observation des Minoritaires Ozone et NOx (SALOMON) show that Aerosols are present in the middle stratosphere, above 25-km altitude. These observations are confirmed by the extinction measurements performed by a solar occultation radiometer. The balloonborne Laboratoire de Meteorologie Dynamique (LMD) counter instrument also confirms the presence of aerosol around 30-km altitude, with an unrealistic excess of micronic particles assuming that only liquid sulfate Aerosols are present. An unexpected spectral structure around 640-nm observed by SALOMON is also detectable in extinction measurements by the satellite instrument Stratospheric Aerosols and Gas Experiment III. This set of measurements could indicate that solid Aerosols were detected at these altitude ranges. The amount of soot detected up to now in the lower stratosphere is too low to explain these measurements. Thus, the presence of interplanetary dust grains and micrometeorites may need to be invoked. Moreover, it seems that these grains fill the stratosphere in stratified layers.
R. Neuber - One of the best experts on this subject based on the ideXlab platform.
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Latitudinal distribution of Stratospheric Aerosols during the EASOE winter 1991/92
Geophysical Research Letters, 1994Co-Authors: R. Neuber, Sophie Godin, Christine David, G. Beyerle, G. Fiocco, A. Di Sarra, K. Fricke, B. Knudsen, L. Stefanutti, G. VaughanAbstract:Lidar measurements of Stratospheric Aerosols were made at several Arctic and mid-latitude stations as part of the European Arctic Stratospheric Ozone Experiment (EASOE) in 1991/92. Volcanic Aerosols were observed throughout the winter at all stations. High latitude stations observed an aerosol-free stratosphere during most of the winter at altitudes above 450 K potential temperature (above 16 km). An even latitudinal distribution of volcanic Aerosols was observed below this level. This is interpreted as indicative of latitudinal transport into the polar region throughout the winter.
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latitudinal distribution of Stratospheric Aerosols during the easoe winter 1991 92
Geophysical Research Letters, 1994Co-Authors: R. Neuber, Sophie Godin, G. Beyerle, G. Fiocco, A. Di Sarra, L. Stefanutti, K H Fricke, Ch David, Bjorn M Knudsen, G. VaughanAbstract:This paper summarizes lidar measurements of Stratospheric Aerosols spanning the latitude range from 44[degrees]N to 79[degrees]N, during the period of the EASOE campaign. The Arctic region measurements show no aerosol content above roughly 16 km, but the density is fairly constant at lower altitudes independent of latitude. The authors argue this indicates latitudinal transport of aerosol throughout the winter.
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multiwavelength lidar measurements of Stratospheric Aerosols above spitsbergen during winter 1992 93
Geophysical Research Letters, 1994Co-Authors: G. Beyerle, R. Neuber, Otto Schrems, F Wittrock, Bjorn M KnudsenAbstract:Within the period of December 1992 to March 1993 lidar investigations of Stratospheric Aerosols were performed at Ny-Alesund, Spitsbergen (79°N, 12°E). Backscatter signals at wavelengths of 353, 532 and 1064 nm and depolarization signals at 532 nm in altitudes ranging from the tropopause up to 30 km were analyzed. Throughout the whole measurement period we observed an aerosol layer of volcanic origin in the lower stratosphere. Depolarization profiles suggest that the volcanic aerosol layer consisted mainly of liquid droplets. Comparison with model calculations indicate median particle radii between 0.1 and 0.2 µm. Surface densities exceeded approximately 40 µm²/cm³ in the lower part of the layer around 12 km. In January 1993 polar Stratospheric clouds (PSCs) were frequently observed at altitudes up to 22 km. We analyzed the backscatter and depolarization data with respect to the temperature history of backward trajectories reaching Ny-Alesund. Signatures for micron sized crystalline PSC particles appear for cooling rates of −1 to −3 K day−1. Larger cooling rates of −4 to −10 K day −1 produced submicron sized Aerosols, presumably supercooled droplets, characterized by enhanced backscatter ratios and reduced depolarization.
I G Usoskin - One of the best experts on this subject based on the ideXlab platform.
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possible effect of extreme solar energetic particle events of september october 1989 on polar Stratospheric Aerosols a case study
Atmospheric Chemistry and Physics, 2013Co-Authors: Irina Mironova, I G UsoskinAbstract:Abstract. The main ionization source of the middle and low Earth's atmosphere is related to energetic particles coming from outer space. Usually it is ionization from cosmic rays that is always present in the atmosphere. But in a case of a very strong solar eruption, some solar energetic particles (SEPs) can reach middle/low atmosphere increasing the ionization rate up to some orders of magnitude at polar latitudes. We continue investigating such a special class of solar events and their possible applications for natural variations of the aerosol content. After the case study of the extreme SEP event of January 2005 and its possible effect upon polar Stratospheric Aerosols, here we analyze atmospheric applications of the sequence of several events that took place over autumn 1989. Using aerosol data obtained over polar regions from two satellites with space-borne optical instruments SAGE II and SAM II that were operating during September–October 1989, we found that an extreme major SEP event might have led to formation of new particles and/or growth of preexisting ultrafine particles in the polar Stratospheric region. However, the effect of the additional ambient air ionization on the aerosol formation is minor, in comparison with temperature effect, and can take place only in the cold polar atmospheric conditions. The extra aerosol mass formed under the temperature effect allows attributing most of the changes to the "ion–aerosol clear sky mechanism".
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possible effect of extreme solar energetic particle event of 20 january 2005 on polar Stratospheric Aerosols direct observational evidence
Atmospheric Chemistry and Physics, 2012Co-Authors: Irina Mironova, I G Usoskin, G A Kovaltsov, S V PetelinaAbstract:Energetic cosmic rays are the main source of ion- ization of the low-middle atmosphere, leading to associated changes in atmospheric properties. Via the hypothetical in- fluence of ionization on aerosol growth and facilitated forma- tion of clouds, this may be an important indirect link relat- ing solar variability to climate. This effect is highly debated, however, since the proposed theoretical mechanisms still re- main illusive and qualitative, and observational evidence is inconclusive and controversial. Therefore, important ques- tions regarding the existence and magnitude of the effect, and particularly the fraction of aerosol particles that can form and grow, are still open. Here we present empirical evidence of the possible effect caused by cosmic rays upon polar strato- spheric Aerosols, based on a case study of an extreme solar energetic particle (SEP) event of 20 January 2005. Using aerosol data obtained over polar regions from different satel- lites with optical instruments that were operating during Jan- uary 2005, such as the Stratospheric Aerosol and Gas Exper- iment III (SAGE III), and Optical Spectrograph and Infrared Imaging System (OSIRIS), we found a significant simulta- neous change in aerosol properties in both the Southern and Northern Polar regions in temporal association with the SEP event. We speculate that ionization of the atmosphere, which was abnormally high in the lower stratosphere during the ex- treme SEP event, might have led to formation of new par- ticles and/or growth of preexisting ultrafine particles in the polar Stratospheric region. However, a detailed interpreta- tion of the effect is left for subsequent studies. This is the first time high vertical resolution measurements have been used to discuss possible production of Stratospheric Aerosols under the influence of cosmic ray induced ionization. The observed effect is marginally detectable for the analyzed se- vere SEP event and can be undetectable for the majority of weak-moderate events. The present interpretation serves as a conservative upper limit of solar energetic particle effect upon polar Stratospheric Aerosols.
