The Experts below are selected from a list of 5712 Experts worldwide ranked by ideXlab platform
Maria Rita Perrone - One of the best experts on this subject based on the ideXlab platform.
-
radiative impact of etna Volcanic Aerosols over south eastern italy on 3 december 2015
Atmospheric Environment, 2018Co-Authors: Salvatore Romano, F. De Tomasi, P Burlizzi, Stefan Kinne, U Hamann, Maria Rita PerroneAbstract:Abstract Irradiance and LiDAR measurements at the surface combined with satellite products from SEVIRI (Spinning Enhanced Visible and InfraRed Imager) and MODIS (MODerate resolution Imaging Spectroradiometer) were used to detect and characterize the Etna volcano (Italy) plume that crossed southeastern Italy on 3 December 2015, from about 10:00 up to 11:30 UTC, and estimate its radiative impact. The Volcanic plume was delivered by a violent and short paroxysmal eruption that occurred from 02:30 to 03:10 UTC of 3 December 2015, about 400 km away from the monitoring site. Measurements from the LiDAR combined with model results showed that the aerosol optical depth of the Volcanic plume, located from about 11 to 13 km above sea level (asl), was equal to 0.80 ± 0.07 at 532 nm. A low tropospheric aerosol load, located up to about 7 km asl, with optical depth equal to 0.19 ± 0.01 at 532 nm was also revealed by the LiDAR measurements. Short-Wave (SW) downward and upward irradiance measurements revealed that the instantaneous SW direct radiative forcing at the surface (DRFsurf) decreased to −146 ± 16 W m−2 at 10:50 UTC because of the Volcanic plume passage. A Two-Stream radiative transfer model integrated with experimental measurements, which took into account the Volcanic plume and the low tropospheric aerosol properties, was used to reproduce the SW radiative flux measurements at the surface and estimate the aerosol DRF both at the top of the atmosphere (TOA) and at the surface, in addition to the aerosol heating rate vertical profile. We found that the clear-sky, instantaneous, SW DRF at the TOA and the atmospheric forcing were equal to −112 and 33 W m-2, respectively, at 10:50 UTC that represented the time at which the Volcanic plume radiative impact was the highest. The SW aerosol heating rate reached the peak value of 1.24 K day−1 at 12 km asl and decreased to −0.06 K day−1 at 11 km asl, at 10:50 UTC. The role of the aerosol load located up to about 7 km asl and the corresponding radiative impact has also been evaluated.
-
Integration of measurements and model simulations to characterize Eyjafjallajökull Volcanic Aerosols over south-eastern Italy
Atmospheric Chemistry and Physics, 2012Co-Authors: Maria Rita Perrone, F. De Tomasi, Andreas Stohl, N. I. KristiansenAbstract:Abstract. Volcanic Aerosols resulting from the Eyjafjallajokull eruption were detected in south-eastern Italy from 20 to 22 April 2010, at a distance of approximately 4000 km from the volcano, and have been characterized by lidar, sun/sky photometer, and surface in-situ measurements. Volcanic particles added to the pre-existing aerosol load and measurement data allow quantifying the impact of Volcanic particles on the aerosol vertical distribution, lidar ratios, the aerosol size distribution, and the ground-level particulate-matter concentrations. Lidar measurements reveal that backscatter coefficients by Volcanic particles were about one order of magnitude smaller over south-eastern Italy than over Central Europe. Mean lidar ratios at 355 nm were equal to 64 ± 5 sr inside the Volcanic aerosol layer and were characterized by smaller values (47 ± 2 sr) in the underlying layer on 20 April, 19:30 UTC. Lidar ratios and their dependence with the height reduced in the following days, mainly because of the variability of the Volcanic particle contributions. Size distributions from sun/sky photometer measurements reveal the presence of Volcanic particles with radii r > 0.5 μm on 21 April and that the contribution of coarse Volcanic particles increased from 20 to 22 April. The aerosol fine mode fraction from sun/sky photometer measurements varied between values of 0.85 and 0.94 on 20 April and decreased to values between 0.25 and 0.82 on 22 April. Surface measurements of particle size distributions were in good accordance with column averaged particle size distributions from sun/sky photometer measurements. PM 1 /PM 2.5 mass concentration ratios of 0.69, 0.66, and 0.60 on 20, 21, and 22 April, respectively, support the increase of super-micron particles at ground. Measurements from the Regional Air Quality Agency show that PM 10 mass concentrations on 20, 21, and 22 April 2010 were enhanced in the entire Apulia Region. More specifically, PM 10 mass concentrations have on average increased over Apulia Region 22%, 50%, and 28% on 20, 21, and 22 April, respectively, compared to values on 19 April. Finally, the comparison of measurement data with numerical simulations by the FLEXPART dispersion model demonstrates the ability of FLEXPART to model the advection of the Volcanic ash over the 4000 km from the Eyjafjallajokull volcano to Southern Italy.
-
Characterization of Eyjafjallajökull Volcanic Aerosols over Southeastern Italy
Atmospheric Chemistry and Physics Discussions, 2012Co-Authors: Maria Rita Perrone, F. De Tomasi, Andreas Stohl, N. I. KristiansenAbstract:Abstract. Volcanic Aerosols resulting from the Eyjafjallajökull eruption have been detected in Southeastern Italy from 20 to 22 April 2010, at a distance of approximately 4000 km from the volcano site, and have been characterized by lidar, sun/sky photometer, and in-situ measurements. Numerical simulations by the FLEXPART dispersion model, meteorological synoptic maps, and analytical backtrajectories confirm the advection of Volcanic Aerosols to the monitoring site. However, both the peak concentrations as well as the total column loadings of Volcanic ash simulated by FLEXPART were about one order of magnitude lower than corresponding values simulated over Central Europe on 16 April. This suggests that the Volcanic ash over Southeastern Italy was strongly diluted. Nevertheless, Volcanic particles added to the pre-existing aerosol load and the integrated use of FLEXPART simulations and experimental measurements has allowed to clearly identifying the impact of Volcanic particles on the aerosol vertical distribution, the aerosol size distribution, and the ground-level particulate-matter concentrations. Lidar measurements performed at the Physics Department of the University of Salento (40.4° N; 18.1° E) within EARLINET (European Aerosol Research LIdar NETwork EARLINET) have revealed the first arrival of Volcanic Aerosols on the afternoon of 20 April. In particular, lidar measurements have shown that at 18:30 UTC of 20 April, lidar ratios (LRs) at 355 nm varied from 65 to 71 sr inside the Volcanic aerosol layer located between 2.5–3.5 km from the ground level and were characterized by smaller values (=~45 sr) in the underlying layer. The LR dependence on altitude has decreased with time as Volcanic particles also reached ground level. Then, LRs varied between 41 and 60 sr all over the aerosol column at 02:30 UTC of 21 April. The time evolution of the aerosol optical depth from lidar measurements was similar to that of the ash-total-column mass concentration from FLEXPART simulations after midday of 21 April, for the larger contribution of Volcanic particles to the whole aerosol load. Sun/sky photometer measurements performed within AERONET, have revealed that the mass size distribution of Volcanic particles retrieved from measurements performed on 21 April was in reasonable accordance with the Volcanic-ash mass size distribution from FLEXPART simulations. Volcanic particles with radius r > 0.5 μm have mainly been advected over Southeastern Italy and the contribution of coarse Volcanic particles has increased from 20 to 22 April. The aerosol fine mode fraction from sun-sky photometer measurements varied between 0.85 and 0.94 on 20 April, but decreased to values between 0.25 and 0.82 on 22 April. Surface measurements of particle size distributions have also supported the advection of coarse Volcanic particles. More specifically, mass concentrations of daily PM1 and PM2.5 samples revealed that the PM1/PM2.5 mass ratios were 0.69, 0.66, and 0.60 on 20, 21, and 22 April, respectively, indicating an increasing fraction of super-micron particles. Finally, measurements from the Regional Air Quality Agency have revealed enhanced PM10 and SO2 mass concentrations on 20, 21 and/or 22 April, 2010 all over the ~400 km long Apulia Region. The estimated enhancement of PM10 from Volcanic particles was ~6 μg m−3 on 21 April at the monitoring site of this study, in satisfactory accordance with FLEXPART simulations.
Gérard Mégie - One of the best experts on this subject based on the ideXlab platform.
-
Polar stratospheric clouds climatology over Dumont d'Urville between 1989 and 1993 and the influence of Volcanic Aerosols on their formation
Journal of Geophysical Research: Atmospheres, 1998Co-Authors: Christine David, Gérard Mégie, Sophie Godin, Slimane Bekki, M. P. ChipperfieldAbstract:The first polar stratospheric clouds (PSCs) climatology ever established from lidar data and relative to a specific site is presented here. It is based on lidar backscatter and depolarization measurements of PSCs carried out between 1989 and 1993 at Dumont d'Urville (66°S, 140°E), which is a primary station of the Network for Detection of Stratospheric Changes (NDSC). The climatology was subdivided based on the stratospheric sulphuric acid aerosol content (background Aerosols in 1989–1991 and Volcanic Aerosols in 1992–1993 following the Mount Pinatubo eruption). PSCs were mainly observed in July and August. Very few water ice clouds (type II) were detected. Most of the PSCs tended to form around the peak in sulphuric acid aerosol, between 17 and 23 km in 1989–1991 and between 11 and 20 km in 1992–1993. This tendency suggests that sulphuric acid Aerosols are very likely to act as condensation nuclei for PSCs. As shown by previous lidar studies [Browell et al, 1990], two type I subclasses were identified: depolarizing (nonspherical) particles (type Ia) and nondepolarizing (spherical) particles (type Ib). No type Ia PSCs were detected above the nitric acid trihydrate (NAT) saturation temperature, TNAT, lending support to the theory that NAT is the main component of type Ia PSCs. There was also no evidence of the existence of sulphuric acid tetrahydrate (SAT) in the data. Some type Ib PSCs were observed close to the frost point, showing that supersaturation with respect to NAT is a necessary, but not sufficient, condition for the existence of solid PSCs. No type Ib PSCs were clearly detected above TNAT in 1989–1991 whereas 18% of the PSCs seem to be found at temperatures above TNAT in 1992–1993. This difference might be linked to the HNO3 uptake by Volcanic sulphuric acid particles starting at higher temperatures. The fraction of type Ia out of the total PSCs observations was lower in 1992–1993 than in 1989–1991. This difference was not found to be highly statistically significant.
-
Correlation of ozone loss with the presence of Volcanic Aerosols
Geophysical Research Letters, 1994Co-Authors: Thomas J. Mcgee, Paul Newman, Upendra Singh, Michael Gross, Sophie Godin, Anne-marie Lacoste, Gérard MégieAbstract:Statistically significant reductions of ozone compared to a climatological profile have been measured above the Observatoire de Haute Provence (OHP) in Southern France (43.9°N, 5.7°E) during the months of July and August, 1992. Lidar profiles of ozone, temperature and Aerosols were recorded on 25 separate nights during that time. The change in the ozone profile is correlated with the presence of Volcanic Aerosols from the eruption of Mt. Pinatubo. The total ozone loss amounts to approximately a 10% reduction in the total ozone column over OHP.
-
Correlation of ozone loss with the presence of Volcanic Aerosols
Geophysical Research Letters, 1994Co-Authors: Thomas J. Mcgee, Anne‐marie ‐m Lacoste, Sylvie Godin, Paul Newman, Upendra Singh, Michael Gross, Gérard MégieAbstract:Statistically significant reductions of ozone compared to a climatological profile have been measured above the Observatoire de Haute Provence (OHP) in Southern France (43.9 deg N, 5.7 deg E) during the months of July and August, 1992. Lidar profiles of ozone, temperature and Aerosols were recorded on 25 separate nights during that time. The change in the ozone profile is correlated with the presence of Volcanic Aerosols from the eruption of Mt. Pinatubo. The total ozone loss amounts to approximately a 10% reduction in the total ozone column over OHP.
Cathy Clerbaux - One of the best experts on this subject based on the ideXlab platform.
-
tracking and quantifying Volcanic so 2 with iasi the september 2007 eruption at jebel at tair
Atmospheric Chemistry and Physics, 2008Co-Authors: Lieven Clarisse, Pierrefrancois Coheur, A J Prata, Daniel Hurtmans, Ariane Razavi, Thierry Phulpin, Juliette Hadjilazaro, Cathy ClerbauxAbstract:In this paper we demonstrate the potential of the infrared Fourier transform spectrometer IASI in analysing Volcanic eruptions, using the September 2007 eruption at Jebel at Tair as an illustrative example. Detailed radiative transfer calculations are presented, simulating IASI-like transmittance spectra for a variety of Volcanic plumes. We analyse the sensitivity of IASI to SO2 at different altitudes and demonstrate that IASI is in principle capable of sensing SO2 down to the surface. Using the brightness temperature difference of well chosen SO2 channels as a filter, we are able to track the plume of the Jebel at Tair eruption for 12 days, on a par with state of the art UV sounders. A method is presented for quickly estimating the altitude of a Volcanic plume based on the relative intensities of the SO2 absorption lines. Despite recent advances, it is still very challenging to retrieve vertical profiles of SO2 from nadir viewing satellites. Currently the most accurate profiles in nadir are retrieved using backtracking of the plume with atmospheric transport models. Via full inverse retrievals using the optimal estimation method, we show the possibility of extracting medium coarse vertical profiles from IASI data. The retrieval allows us to present an evolution of the total mass of SO2 in the plume for the Jebel at Tair eruption. An analytical relation is derived between brightness temperature differences and concentrations, which fits the experimental data very well. The spectral range of IASI also allows retrieval of Volcanic Aerosols. In the initial plume of the Jebel at Tair eruption, Volcanic Aerosols were found in the form of ice particles, for which we derived particle sizes.
-
Tracking and quantifying Volcanic SO2 with IASI, the September 2007 eruption at Jebel at Tair
Atmospheric Chemistry and Physics, 2008Co-Authors: Lieven Clarisse, Pierrefrancois Coheur, A J Prata, Daniel Hurtmans, Ariane Razavi, Thierry Phulpin, Juliette Hadji-lazaro, Cathy ClerbauxAbstract:In this paper we demonstrate the potential of the infrared Fourier transform spectrometer IASI in analysing Volcanic eruptions, using the September 2007 eruption at Jebel at Tair as an illustrative example. Detailed radiative transfer calculations are presented, simulating IASI-like transmittance spectra for a variety of Volcanic plumes. We analyse the sensitivity of IASI to SO2 at different altitudes and demonstrate that IASI is in principle capable of sensing SO2 down to the surface. Using the brightness temperature difference of well chosen SO2 channels as a filter, we are able to track the plume of the Jebel at Tair eruption for 12 days, on a par with state of the art UV sounders. A method is presented for quickly estimating the altitude of a Volcanic plume based on the relative intensities of the SO2 absorption lines. Despite recent advances, it is still very challenging to retrieve vertical profiles of SO2 from nadir viewing satellites. Currently the most accurate profiles in nadir are retrieved using backtracking of the plume with atmospheric transport models. Via full inverse retrievals using the optimal estimation method, we show the possibility of extracting medium coarse vertical profiles from IASI data. The retrieval allows us to present an evolution of the total mass of SO2 in the plume for the Jebel at Tair eruption. An analytical relation is derived between brightness temperature differences and concentrations, which fits the experimental data very well. The spectral range of IASI also allows retrieval of Volcanic Aerosols. In the initial plume of the Jebel at Tair eruption, Volcanic Aerosols were found in the form of ice particles, for which we derived particle sizes.
Daniel N. Baker - One of the best experts on this subject based on the ideXlab platform.
-
stratospheric Volcanic Aerosols and changes in air earth current density at solar wind magnetic sector boundaries as conditions for the wilcox tropospheric vorticity effect
Journal of Geophysical Research, 1994Co-Authors: Brian A. Tinsley, Todd J Hoeksema, Daniel N. BakerAbstract:A correlation between tropospheric dynamics and solar wind magnetic fields that disappeared in the early 1970s reappeared with a new injection of Volcanic Aerosols into the stratosphere. A similar pattern of correlation has been found for changes in current density in the global electric circuit and for changes in relativistic electron precipitation. Several other weather and climate variations have been found to correlate with changes in air-earth current density due to solar wind modulation of the global electric circuit. The accumulation of electrostatic charge on supercooled droplets at cloud tops responds to air-earth current density changes. A mechanism linking the effects of charge accumulation to changes in ice nucleation, precipitation efficiency, latent heat retention and perturbations in atmospheric dynamics is thus as an explanation for this and other solar wind - atmospheric electricity - weather and climate correlations.
-
Stratospheric Volcanic Aerosols and changes in air‐earth current density at solar wind magnetic sector boundaries as conditions for the Wilcox tropospheric vorticity effect
Journal of Geophysical Research, 1994Co-Authors: Brian A. Tinsley, J. Todd Hoeksema, Daniel N. BakerAbstract:A correlation between tropospheric dynamics and solar wind magnetic fields that disappeared in the early 1970s reappeared with a new injection of Volcanic Aerosols into the stratosphere. A similar pattern of correlation has been found for changes in current density in the global electric circuit and for changes in relativistic electron precipitation. Several other weather and climate variations have been found to correlate with changes in air-earth current density due to solar wind modulation of the global electric circuit. The accumulation of electrostatic charge on supercooled droplets at cloud tops responds to air-earth current density changes. A mechanism linking the effects of charge accumulation to changes in ice nucleation, precipitation efficiency, latent heat retention and perturbations in atmospheric dynamics is thus as an explanation for this and other solar wind - atmospheric electricity - weather and climate correlations.
Thomas J. Mcgee - One of the best experts on this subject based on the ideXlab platform.
-
Correlation of ozone loss with the presence of Volcanic Aerosols
Geophysical Research Letters, 1994Co-Authors: Thomas J. Mcgee, Paul Newman, Upendra Singh, Michael Gross, Sophie Godin, Anne-marie Lacoste, Gérard MégieAbstract:Statistically significant reductions of ozone compared to a climatological profile have been measured above the Observatoire de Haute Provence (OHP) in Southern France (43.9°N, 5.7°E) during the months of July and August, 1992. Lidar profiles of ozone, temperature and Aerosols were recorded on 25 separate nights during that time. The change in the ozone profile is correlated with the presence of Volcanic Aerosols from the eruption of Mt. Pinatubo. The total ozone loss amounts to approximately a 10% reduction in the total ozone column over OHP.
-
Correlation of ozone loss with the presence of Volcanic Aerosols
Geophysical Research Letters, 1994Co-Authors: Thomas J. Mcgee, Anne‐marie ‐m Lacoste, Sylvie Godin, Paul Newman, Upendra Singh, Michael Gross, Gérard MégieAbstract:Statistically significant reductions of ozone compared to a climatological profile have been measured above the Observatoire de Haute Provence (OHP) in Southern France (43.9 deg N, 5.7 deg E) during the months of July and August, 1992. Lidar profiles of ozone, temperature and Aerosols were recorded on 25 separate nights during that time. The change in the ozone profile is correlated with the presence of Volcanic Aerosols from the eruption of Mt. Pinatubo. The total ozone loss amounts to approximately a 10% reduction in the total ozone column over OHP.
-
Raman dial measurements of stratospheric ozone in the presence of Volcanic Aerosols
Geophysical Research Letters, 1993Co-Authors: Thomas J. Mcgee, Michael R. Gross, Richard Ferrare, William S. Heaps, Upendra N. SinghAbstract:Since the eruption of Mt. Pinatubo in June, 1991, measurements of atmospheric species which depend on Rayleigh scattering of radiation, have been severely compromised where the Volcanic aerosol cloud exists. For the GSFC stratospheric ozone lidar, this has meant that ozone determination has been impossible below approximately 30 km. The GSFC lidar has been modified to detect Raman scattering from nitrogen molecules from transmitted laser wavelengths. The instrument transmits two laser wavelengths at 308 nm and 351 nm, and detects returns at four wavelengths; 308 nm, 332 nm, 351 nm, and 382 nm. Using this technique in conjunction with the Rayleigh DIAL measurement, ozone profiles have been measured between 15 and 50 km.
