Fabrizio Ravegnani - Academia.edu (original) (raw)
Papers by Fabrizio Ravegnani
Optical Remote Sensing of the Atmosphere and Clouds, 1998
During the last few years UV-Vis spectrometers were developed at the FISBAT Institute and are use... more During the last few years UV-Vis spectrometers were developed at the FISBAT Institute and are used for application of differential optical absorption spectroscopy method to detect many atmospheric trace gases playing important roles in the stratospheric chemistry. After several test both ...
Pure Lagrangian, i.e., trajectory-based transport models, take into account only the resolved adv... more Pure Lagrangian, i.e., trajectory-based transport models, take into account only the resolved advective part of transport. That means neither mixing processes between the air parcels (APs) nor unresolved subgrid-scale advective processes like convection are included. The Chemical Lagrangian Model of the Stratosphere (CLaMS 1.0) extends this approach by including mixing between the Lagrangian APs parameterizing the small-scale isentropic mixing. To improve model representation of the upper troposphere and lower stratosphere (UTLS), this approach was extended by taking into account parameterization of tropospheric mixing and unresolved convection in the recently published CLaMS 2.0 version. All three transport modes, i.e., isentropic and tropospheric mixing and the unresolved convection can be adjusted and optimized within the model. Here, we investigate the sensitivity of the model representation of tracers in the UTLS with respect to these three modes. For this reason, the CLaMS 2.0 version implemented within the Modular Earth Submodel System (MESSy), CLaMS 2.0/MESSy, is applied with meteorology based on the ERA-Interim (EI) and ERA5 (E5) reanalyses with the same horizontal resolution (1.0 × 1.0 •) but with 60 and 137 model levels for EI and E5, respectively. Comparisons with in situ observations are used to rate the degree of agreement between different model configurations and observations. Starting from pure advective runs as a reference and in agreement with CLaMS 1.0, we show that among the three processes considered, isentropic mixing dominates transport in the UTLS. Both the observed CO, O 3 , N 2 O, and CO 2 profiles and COO 3 correlations are clearly better reproduced in the model with isentropic mixing. The second most important transport process considered is convection which is only partially resolved in the vertical velocity fields provided by the analysis. This additional pathway of transport from the planetary boundary layer (PBL) to the main convective outflow dominates the composition of air in the lower stratosphere relative to the contribution of the resolved transport. This transport happens mainly in the tropics and sub-tropics, and significantly rejuvenates the age of air in this region. By taking into account tropospheric mixing, weakest changes in tracer distributions without any clear improvements were found. 1 Introduction Timescales of transport from the Earth's surface into the upper troposphere and lower stratosphere (UTLS) determine chemical composition of this region and, consequently, influence the Earth's radiation budget and surface tempera-Published by Copernicus Publications on behalf of the European Geosciences Union.
Journal of Geophysical Research, 2002
During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of ... more During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar stratospheric clouds (PSCs) lead to elevated abundances of chlorine monoxide (ClO) that, in the presence of sunlight, destroy ozone. Here we show that PSCs were more widespread during the 1999/2000 Arctic winter than for any other Arctic winter in the past two decades. We have used three fundamentally different approaches to derive the degree of chemical ozone loss from ozonesonde, balloon, aircraft, and satellite instruments. We show that the ozone losses derived from these different instruments and approaches agree very well, resulting in a high level of confidence in the results. Chemical processes led to a 70% reduction of ozone for a region $1 km thick of the lower stratosphere, the largest degree of local loss ever reported for the Arctic. The Match analysis of ozonesonde data shows that the accumulated chemical loss of ozone inside the Arctic vortex totaled 117 ± 14 Dobson units (DU) by the end of winter. This loss, combined with dynamical redistribution of air parcels, resulted in a 88 ± 13 DU reduction in total column ozone compared to the amount that would have been present in the
Atmospheric Chemistry and Physics, 2011
We present the analysis of the impact of convection on the composition of the tropical tropopause... more We present the analysis of the impact of convection on the composition of the tropical tropopause layer region (TTL) in West-Africa during the AMMA-SCOUT campaign. Geophysica M55 aircraft observations of water vapor, ozone, aerosol and CO 2 during August 2006 show perturbed values at altitudes ranging from 14 km to 17 km (above the main convective outflow) and satellite data indicates that air detrainment is likely to have originated from convective cloud east of the flights. Simulations of the BO-LAM mesoscale model, nudged with infrared radiance temperatures, are used to estimate the convective impact in the upper troposphere and to assess the fraction of air processed by convection. The analysis shows that BOLAM correctly reproduces the location and the vertical structure of convective outflow. Model-aided analysis indicates that convection can influence the composition of the upper troposphere above the level of main outflow for an event of deep convection close to the observation site. Model analysis also shows that deep convection occurring in the entire Sahelian transect (up to 2000 km E of the measurement area) has a non negligible role in determining TTL composition.
Annals of Geophysics, 2009
In the field of air quality control, optical remote sensing systems can measure the spatial distr... more In the field of air quality control, optical remote sensing systems can measure the spatial distribution of gas pollutants, offering numerous advantages over conventional networks of in situ analysers. We propose some innovative solutions in the field of DOAS (Differential Optical Absorption Spectroscopy) remote systems, utilizing diffuse solar light as the radiation source. We examine the numerous potentialities of minor gas slant column calculations, applying the «off-axis» methodology for collecting the diffuse solar radiation. One of these particular approaches, using measurements along horizontal paths, has already been tested with the spectrometer installed on board the Geophysica aircraft during stratospheric flights up to altitudes of 20 km. The theoretical basis of these new measurement techniques using DOAS remote sensing systems are delineated to assess whether low altitude flights can provide 2D and 3D pollution tomography over metropolitan areas. The 2D or 3D trace gas total column mapping could be used to investigate: i) transport and dispersion phenomena of air pollution, ii) photochemical process rates, iii) gas plume tomography, iv) minor gas vertical profiles into the Planetary Boundary Layer and v) minor gas flux divergence over a large area.
NanoImpact, 2020
Influence of spray-coating process parameters on the release of TiO2 particles for the production... more Influence of spray-coating process parameters on the release of TiO2 particles for the production of antibacterial textile, NANOIMPACT (2020),
Proceedings of SPIE - The International Society for Optical Engineering, 2009
... As described in section 4.1 for NO2, also for O3 the determination of the vertical profiles i... more ... As described in section 4.1 for NO2, also for O3 the determination of the vertical profiles is obtained with the application of the Chahine inversion algorithm to the observed SCD. The input data of the tool utilized for the retrieval of the Proc. ... [22] Kondo, Y., Mathews, AW, Solomon ...
Optics Express, 2012
This paper describes the radiative transfer model (RTM) MOCRA (MOnte Carlo Radiance Analysis), de... more This paper describes the radiative transfer model (RTM) MOCRA (MOnte Carlo Radiance Analysis), developed in the frame of DOAS (Differential Optical Absorption Spectroscopy) to correctly interpret remote sensing measurements of trace gas amounts in the atmosphere through the calculation of the Air Mass Factor. Besides the DOAS-related quantities, the MOCRA code yields: 1-the atmospheric transmittance in the vertical and sun directions, 2-the direct and global irradiance, 3-the singleand multiple-scattered radiance for a detector with assigned position, line of sight and field of view. Sample calculations of the main radiometric quantities calculated with MOCRA are presented and compared with the output of another RTM (MODTRAN4). A further comparison is presented between the NO2 slant column densities (SCDs) measured with DOAS at Evora (Portugal) and the ones simulated with MOCRA. Both comparisons (MOCRA-MODTRAN4 and MOCRA-observations) gave more than satisfactory results, and overall make MOCRA a versatile tool for atmospheric radiative transfer simulations and interpretation of remote sensing measurements.
Journal of Geophysical Research, 2000
The first deployment of the ECOC electro chemical ozone cell (ECOC) instrument onboard the high-a... more The first deployment of the ECOC electro chemical ozone cell (ECOC) instrument onboard the high-altitude research aircraft, the Geophysica M-55, took place from Rovaniemi, northern Finland, between December 23, 1996, and January 14, 1997. The ECOC data were compared against contemporaneous data from a network of balloon-borne ozone sondes. The comparison was carried out in potential vorticity-potential temperature (PV, ©) coordinates, using meteorological analyses from the European Centre for Medium-Range Forecasts. The comparison showed that ozone mixing ratios measured by ECOC are lower than those measured by ozonesonde by a small but statistically significant bias of (-5.7 5: 2.8)% at the cruising altitudes of the aircraft, 15 to 19 km. After establishing and removing the average bias, ECOC and ozonesonde data were analyzed together to follow the development of ozone distributions in the early winter Arctic stratosphere. The analysis showed no evidence of chemical ozone depletion at the cruising altitudes of the aircraft, that is, between 435 and 490 K. The absence of chemical depletion is in agreement with polar statospheric cloud (PSC) observations, which showed no PSCs at aircraft cruising altitudes, although from January 5 onwards, PSCs were observed above cruising altitudes. Results from a three-dimensional chemical transport model reproduce the basic features of the reconstructed ozone fields. However, the model does not capture the observed ozone increase during the campaign, due to weak modeled ozone vertical gradients, and indicates small ozone depletion of about 3% inside the vortex at 480 K by mid January.
IEEE Transactions on Geoscience and Remote Sensing, 2014
ABSTRACT A geometrical method to determine the vertical distribution of a trace gas in the lower ... more ABSTRACT A geometrical method to determine the vertical distribution of a trace gas in the lower troposphere is presented. The technique is based on quasi-simultaneous measurements of diffuse solar radiation with spectrometric equipment observing the atmosphere from different viewing directions and a measurement of a distant lamp. Differential optical absorption spectroscopy (DOAS) algorithms are applied to retrieve the slant column densities (SCDs) of the analyzed compound. A recursive procedure involving the set of observed SCDs, the geometry of measurement, and several offline radiative transfer simulations provides the vertical profile of the target trace gas. This technique is applied to nitrogen dioxide (NO2) SCDs, and the results are compared to the output of the modeling system Gas Aerosol Modeling Evaluation System (GAMES). The correlation coefficient between the DOAS and GAMES NO2 concentration profiles is 0.7 and shows a nonnegligible variability as a function of altitude and sky conditions.
Atmospheric Chemistry and Physics, 2011
In situ measurements of ice crystal size distributions in tropical upper troposphere/lower strato... more In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to
Atmospheric Chemistry and Physics, 2010
Processes occurring in the tropical upper troposphere (UT), the Tropical Transition Layer (TTL), ... more Processes occurring in the tropical upper troposphere (UT), the Tropical Transition Layer (TTL), and the lower stratosphere (LS) are of importance for the global climate, for stratospheric dynamics and air chemistry, and for their influence on the global distribution of water vapour, trace gases and aerosols. In this contribution we present aerosol and trace gas (in-situ) measurements from the tropical UT/LS over Southern Brazil, Northern Australia, and West Africa. The instruments were operated on board of the Russian high altitude research aircraft M-55 "Geophysica" and the DLR Falcon-20 during the campaigns TROCCI
Atmospheric Chemistry and Physics, 2011
Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Br... more Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Brazil, February 2005) and SCOUT-O 3 (Darwin, Australia, November/December 2005) field campaigns. While during most flights significant amounts of ClO (≈10-20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt-significantly exceeding those expected from gas phase chemistry-were observed in air masses of a more tropospheric character. Most of these observations are associated with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid aerosol at low temperatures may promote significant heterogeneous chlorine activation in the tropical upper troposphere lower stratosphere (UTLS). In two case studies, particularly high levels of ClO observed were reproduced by chemistry simulations only under the assumption that significant denoxification had occurred in the observed air. However, to reproduce the ClO observations in these simulations, O 3 mixing ratios higher than observed had to be assumed, and at least for one of these flights, a significant denoxification is in contrast to the observed NO levels, suggesting that the coupling of chlorine and nitrogen compounds in the tropical UTLS may not be completely understood.
Atmospheric Chemistry and Physics, 2008
During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric res... more During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric research aircraft M55 Geophysica performed a flight over and within the inner core region of tropical cyclone Davina. Measurements of total water, water vapour, temperature, aerosol backscattering, ozone and tracers were made and are discussed here in comparison with the averages of those quantities acquired during the campaign time frame. Temperature anomalies in the tropical tropopause layer (TTL), warmer than average in the lower part and colder than average in the upper TTL were observed. Ozone was strongly reduced compared to its average value, and thick cirrus decks were present up to the cold point, sometimes topped by a layer of very dry air. Evidence for meridional transport of trace gases in the stratosphere above the cyclone was observed and perturbed water distribution in the TTL was documented. The paper discuss possible processes of dehydration induced by the cirrus forming above the cyclone, and change in the chemical tracer and water distribution in the lower stratosphere 400-430 K due to meridional transport from the mid-latitudes and link with Davina. Moreover it compares the data prior and after the cyclone passage to discuss its actual impact on the atmospheric chemistry and thermodynamics.
Atti della Fondazione …, 2007
The validation of cloud top and ozone vertical column, measured by SCIAMA-CHY, were carried out r... more The validation of cloud top and ozone vertical column, measured by SCIAMA-CHY, were carried out respectively by lidars and in-situ and remote-sensing ozone instruments on-board the high altitude Geophysica aircraft. Cloud top and ozone measurements were conducted during the transfer flights of the Geophysica from Europe to Brazil and in the Tropics, from Araçatuba, from January to the end of February 2005. The Validation campaign, financed by ESA, was embedded within a scientific campaign in the frame of two EC projects: APE-INFRA and Troccinox. Validation of MIPAS-ENVISAT products were planned by means of the corresponding instrument MIPAS-STR which was also on-board the Geophysica, and by means of other in-situ instruments. Some results of MIPAS-STR are reported here; however, the MIPAS data from the ENVISAT are not available. In general the validations show some discrepancies between the data collected by the Geophysica and the instruments on board of ENVISAT, which cannot easily be explained by the displacement of the satellite and aircraft measurements.
Ground-based zenith sky Differential Optical Absorption Spectroscopy (DOAS) measurements performe... more Ground-based zenith sky Differential Optical Absorption Spectroscopy (DOAS) measurements performed by means of GASCOD instruments at Mt. Cimone (44N 11E), Italy and Stara Zagora (42N, 25E), Bulgaria are used for validation of SCIAMACHY NO 2 vertical column density (vcd) of ESA SCI_NL product retrieved with 5.01 processor version. The results presented in this work regard satellite data for the July-December 2002 period. On this base it is concluded that during summer-autumn period the overall NO 2 vcd above both stations is fairly well reproduced by the SCIAMACHY data, while towards the winter period they deviate from the seasonal behaviour of NO 2 vcd derived at both stations.
Advances in Space Research, 2005
A correct interpretation of diffuse solar radiation measurements made by Differential Optical Abs... more A correct interpretation of diffuse solar radiation measurements made by Differential Optical Absorption Spectroscopy (DOAS) remote sensors require the use of radiative transfer models of the atmosphere. The simplest models consider radiation scattering in the atmosphere as a single scattering process. More realistic atmospheric models are those which consider multiple scattering and their application is useful and essential for the analysis of zenith and off-axis measurements regarding the lowest layers of the atmosphere, such as the boundary layer. These are characterized by the highest values of air density and quantities of particles and aerosols acting as scattering nuclei. A new atmospheric model, PROcessing of Multi-Scattered Atmospheric Radiation (PROMSAR), which includes multiple Rayleigh and Mie scattering, has recently been developed at ISAC-CNR. It is based on a backward Monte Carlo technique which is very suitable for studying the various interactions taking place in a complex and non-homogeneous system like the terrestrial atmosphere. PROMSAR code calculates the mean path of the radiation within each layer in which the atmosphere is subdivided taking into account the large variety of processes that solar radiation undergoes during propagation through the atmosphere. This quantity is then employed to work out the Air Mass Factor (AMF) of several trace gases, to simulate in zenith and off-axis configurations their slant column amounts and to calculate the weighting functions from which informations about the gas vertical distribution is obtained using inversion methods. Results from the model, simulations and comparisons with actual slant column measurements are presented and discussed.
Optical Remote Sensing of the Atmosphere and Clouds, 1998
During the last few years UV-Vis spectrometers were developed at the FISBAT Institute and are use... more During the last few years UV-Vis spectrometers were developed at the FISBAT Institute and are used for application of differential optical absorption spectroscopy method to detect many atmospheric trace gases playing important roles in the stratospheric chemistry. After several test both ...
Pure Lagrangian, i.e., trajectory-based transport models, take into account only the resolved adv... more Pure Lagrangian, i.e., trajectory-based transport models, take into account only the resolved advective part of transport. That means neither mixing processes between the air parcels (APs) nor unresolved subgrid-scale advective processes like convection are included. The Chemical Lagrangian Model of the Stratosphere (CLaMS 1.0) extends this approach by including mixing between the Lagrangian APs parameterizing the small-scale isentropic mixing. To improve model representation of the upper troposphere and lower stratosphere (UTLS), this approach was extended by taking into account parameterization of tropospheric mixing and unresolved convection in the recently published CLaMS 2.0 version. All three transport modes, i.e., isentropic and tropospheric mixing and the unresolved convection can be adjusted and optimized within the model. Here, we investigate the sensitivity of the model representation of tracers in the UTLS with respect to these three modes. For this reason, the CLaMS 2.0 version implemented within the Modular Earth Submodel System (MESSy), CLaMS 2.0/MESSy, is applied with meteorology based on the ERA-Interim (EI) and ERA5 (E5) reanalyses with the same horizontal resolution (1.0 × 1.0 •) but with 60 and 137 model levels for EI and E5, respectively. Comparisons with in situ observations are used to rate the degree of agreement between different model configurations and observations. Starting from pure advective runs as a reference and in agreement with CLaMS 1.0, we show that among the three processes considered, isentropic mixing dominates transport in the UTLS. Both the observed CO, O 3 , N 2 O, and CO 2 profiles and COO 3 correlations are clearly better reproduced in the model with isentropic mixing. The second most important transport process considered is convection which is only partially resolved in the vertical velocity fields provided by the analysis. This additional pathway of transport from the planetary boundary layer (PBL) to the main convective outflow dominates the composition of air in the lower stratosphere relative to the contribution of the resolved transport. This transport happens mainly in the tropics and sub-tropics, and significantly rejuvenates the age of air in this region. By taking into account tropospheric mixing, weakest changes in tracer distributions without any clear improvements were found. 1 Introduction Timescales of transport from the Earth's surface into the upper troposphere and lower stratosphere (UTLS) determine chemical composition of this region and, consequently, influence the Earth's radiation budget and surface tempera-Published by Copernicus Publications on behalf of the European Geosciences Union.
Journal of Geophysical Research, 2002
During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of ... more During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar stratospheric clouds (PSCs) lead to elevated abundances of chlorine monoxide (ClO) that, in the presence of sunlight, destroy ozone. Here we show that PSCs were more widespread during the 1999/2000 Arctic winter than for any other Arctic winter in the past two decades. We have used three fundamentally different approaches to derive the degree of chemical ozone loss from ozonesonde, balloon, aircraft, and satellite instruments. We show that the ozone losses derived from these different instruments and approaches agree very well, resulting in a high level of confidence in the results. Chemical processes led to a 70% reduction of ozone for a region $1 km thick of the lower stratosphere, the largest degree of local loss ever reported for the Arctic. The Match analysis of ozonesonde data shows that the accumulated chemical loss of ozone inside the Arctic vortex totaled 117 ± 14 Dobson units (DU) by the end of winter. This loss, combined with dynamical redistribution of air parcels, resulted in a 88 ± 13 DU reduction in total column ozone compared to the amount that would have been present in the
Atmospheric Chemistry and Physics, 2011
We present the analysis of the impact of convection on the composition of the tropical tropopause... more We present the analysis of the impact of convection on the composition of the tropical tropopause layer region (TTL) in West-Africa during the AMMA-SCOUT campaign. Geophysica M55 aircraft observations of water vapor, ozone, aerosol and CO 2 during August 2006 show perturbed values at altitudes ranging from 14 km to 17 km (above the main convective outflow) and satellite data indicates that air detrainment is likely to have originated from convective cloud east of the flights. Simulations of the BO-LAM mesoscale model, nudged with infrared radiance temperatures, are used to estimate the convective impact in the upper troposphere and to assess the fraction of air processed by convection. The analysis shows that BOLAM correctly reproduces the location and the vertical structure of convective outflow. Model-aided analysis indicates that convection can influence the composition of the upper troposphere above the level of main outflow for an event of deep convection close to the observation site. Model analysis also shows that deep convection occurring in the entire Sahelian transect (up to 2000 km E of the measurement area) has a non negligible role in determining TTL composition.
Annals of Geophysics, 2009
In the field of air quality control, optical remote sensing systems can measure the spatial distr... more In the field of air quality control, optical remote sensing systems can measure the spatial distribution of gas pollutants, offering numerous advantages over conventional networks of in situ analysers. We propose some innovative solutions in the field of DOAS (Differential Optical Absorption Spectroscopy) remote systems, utilizing diffuse solar light as the radiation source. We examine the numerous potentialities of minor gas slant column calculations, applying the «off-axis» methodology for collecting the diffuse solar radiation. One of these particular approaches, using measurements along horizontal paths, has already been tested with the spectrometer installed on board the Geophysica aircraft during stratospheric flights up to altitudes of 20 km. The theoretical basis of these new measurement techniques using DOAS remote sensing systems are delineated to assess whether low altitude flights can provide 2D and 3D pollution tomography over metropolitan areas. The 2D or 3D trace gas total column mapping could be used to investigate: i) transport and dispersion phenomena of air pollution, ii) photochemical process rates, iii) gas plume tomography, iv) minor gas vertical profiles into the Planetary Boundary Layer and v) minor gas flux divergence over a large area.
NanoImpact, 2020
Influence of spray-coating process parameters on the release of TiO2 particles for the production... more Influence of spray-coating process parameters on the release of TiO2 particles for the production of antibacterial textile, NANOIMPACT (2020),
Proceedings of SPIE - The International Society for Optical Engineering, 2009
... As described in section 4.1 for NO2, also for O3 the determination of the vertical profiles i... more ... As described in section 4.1 for NO2, also for O3 the determination of the vertical profiles is obtained with the application of the Chahine inversion algorithm to the observed SCD. The input data of the tool utilized for the retrieval of the Proc. ... [22] Kondo, Y., Mathews, AW, Solomon ...
Optics Express, 2012
This paper describes the radiative transfer model (RTM) MOCRA (MOnte Carlo Radiance Analysis), de... more This paper describes the radiative transfer model (RTM) MOCRA (MOnte Carlo Radiance Analysis), developed in the frame of DOAS (Differential Optical Absorption Spectroscopy) to correctly interpret remote sensing measurements of trace gas amounts in the atmosphere through the calculation of the Air Mass Factor. Besides the DOAS-related quantities, the MOCRA code yields: 1-the atmospheric transmittance in the vertical and sun directions, 2-the direct and global irradiance, 3-the singleand multiple-scattered radiance for a detector with assigned position, line of sight and field of view. Sample calculations of the main radiometric quantities calculated with MOCRA are presented and compared with the output of another RTM (MODTRAN4). A further comparison is presented between the NO2 slant column densities (SCDs) measured with DOAS at Evora (Portugal) and the ones simulated with MOCRA. Both comparisons (MOCRA-MODTRAN4 and MOCRA-observations) gave more than satisfactory results, and overall make MOCRA a versatile tool for atmospheric radiative transfer simulations and interpretation of remote sensing measurements.
Journal of Geophysical Research, 2000
The first deployment of the ECOC electro chemical ozone cell (ECOC) instrument onboard the high-a... more The first deployment of the ECOC electro chemical ozone cell (ECOC) instrument onboard the high-altitude research aircraft, the Geophysica M-55, took place from Rovaniemi, northern Finland, between December 23, 1996, and January 14, 1997. The ECOC data were compared against contemporaneous data from a network of balloon-borne ozone sondes. The comparison was carried out in potential vorticity-potential temperature (PV, ©) coordinates, using meteorological analyses from the European Centre for Medium-Range Forecasts. The comparison showed that ozone mixing ratios measured by ECOC are lower than those measured by ozonesonde by a small but statistically significant bias of (-5.7 5: 2.8)% at the cruising altitudes of the aircraft, 15 to 19 km. After establishing and removing the average bias, ECOC and ozonesonde data were analyzed together to follow the development of ozone distributions in the early winter Arctic stratosphere. The analysis showed no evidence of chemical ozone depletion at the cruising altitudes of the aircraft, that is, between 435 and 490 K. The absence of chemical depletion is in agreement with polar statospheric cloud (PSC) observations, which showed no PSCs at aircraft cruising altitudes, although from January 5 onwards, PSCs were observed above cruising altitudes. Results from a three-dimensional chemical transport model reproduce the basic features of the reconstructed ozone fields. However, the model does not capture the observed ozone increase during the campaign, due to weak modeled ozone vertical gradients, and indicates small ozone depletion of about 3% inside the vortex at 480 K by mid January.
IEEE Transactions on Geoscience and Remote Sensing, 2014
ABSTRACT A geometrical method to determine the vertical distribution of a trace gas in the lower ... more ABSTRACT A geometrical method to determine the vertical distribution of a trace gas in the lower troposphere is presented. The technique is based on quasi-simultaneous measurements of diffuse solar radiation with spectrometric equipment observing the atmosphere from different viewing directions and a measurement of a distant lamp. Differential optical absorption spectroscopy (DOAS) algorithms are applied to retrieve the slant column densities (SCDs) of the analyzed compound. A recursive procedure involving the set of observed SCDs, the geometry of measurement, and several offline radiative transfer simulations provides the vertical profile of the target trace gas. This technique is applied to nitrogen dioxide (NO2) SCDs, and the results are compared to the output of the modeling system Gas Aerosol Modeling Evaluation System (GAMES). The correlation coefficient between the DOAS and GAMES NO2 concentration profiles is 0.7 and shows a nonnegligible variability as a function of altitude and sky conditions.
Atmospheric Chemistry and Physics, 2011
In situ measurements of ice crystal size distributions in tropical upper troposphere/lower strato... more In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to
Atmospheric Chemistry and Physics, 2010
Processes occurring in the tropical upper troposphere (UT), the Tropical Transition Layer (TTL), ... more Processes occurring in the tropical upper troposphere (UT), the Tropical Transition Layer (TTL), and the lower stratosphere (LS) are of importance for the global climate, for stratospheric dynamics and air chemistry, and for their influence on the global distribution of water vapour, trace gases and aerosols. In this contribution we present aerosol and trace gas (in-situ) measurements from the tropical UT/LS over Southern Brazil, Northern Australia, and West Africa. The instruments were operated on board of the Russian high altitude research aircraft M-55 "Geophysica" and the DLR Falcon-20 during the campaigns TROCCI
Atmospheric Chemistry and Physics, 2011
Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Br... more Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Brazil, February 2005) and SCOUT-O 3 (Darwin, Australia, November/December 2005) field campaigns. While during most flights significant amounts of ClO (≈10-20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt-significantly exceeding those expected from gas phase chemistry-were observed in air masses of a more tropospheric character. Most of these observations are associated with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid aerosol at low temperatures may promote significant heterogeneous chlorine activation in the tropical upper troposphere lower stratosphere (UTLS). In two case studies, particularly high levels of ClO observed were reproduced by chemistry simulations only under the assumption that significant denoxification had occurred in the observed air. However, to reproduce the ClO observations in these simulations, O 3 mixing ratios higher than observed had to be assumed, and at least for one of these flights, a significant denoxification is in contrast to the observed NO levels, suggesting that the coupling of chlorine and nitrogen compounds in the tropical UTLS may not be completely understood.
Atmospheric Chemistry and Physics, 2008
During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric res... more During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric research aircraft M55 Geophysica performed a flight over and within the inner core region of tropical cyclone Davina. Measurements of total water, water vapour, temperature, aerosol backscattering, ozone and tracers were made and are discussed here in comparison with the averages of those quantities acquired during the campaign time frame. Temperature anomalies in the tropical tropopause layer (TTL), warmer than average in the lower part and colder than average in the upper TTL were observed. Ozone was strongly reduced compared to its average value, and thick cirrus decks were present up to the cold point, sometimes topped by a layer of very dry air. Evidence for meridional transport of trace gases in the stratosphere above the cyclone was observed and perturbed water distribution in the TTL was documented. The paper discuss possible processes of dehydration induced by the cirrus forming above the cyclone, and change in the chemical tracer and water distribution in the lower stratosphere 400-430 K due to meridional transport from the mid-latitudes and link with Davina. Moreover it compares the data prior and after the cyclone passage to discuss its actual impact on the atmospheric chemistry and thermodynamics.
Atti della Fondazione …, 2007
The validation of cloud top and ozone vertical column, measured by SCIAMA-CHY, were carried out r... more The validation of cloud top and ozone vertical column, measured by SCIAMA-CHY, were carried out respectively by lidars and in-situ and remote-sensing ozone instruments on-board the high altitude Geophysica aircraft. Cloud top and ozone measurements were conducted during the transfer flights of the Geophysica from Europe to Brazil and in the Tropics, from Araçatuba, from January to the end of February 2005. The Validation campaign, financed by ESA, was embedded within a scientific campaign in the frame of two EC projects: APE-INFRA and Troccinox. Validation of MIPAS-ENVISAT products were planned by means of the corresponding instrument MIPAS-STR which was also on-board the Geophysica, and by means of other in-situ instruments. Some results of MIPAS-STR are reported here; however, the MIPAS data from the ENVISAT are not available. In general the validations show some discrepancies between the data collected by the Geophysica and the instruments on board of ENVISAT, which cannot easily be explained by the displacement of the satellite and aircraft measurements.
Ground-based zenith sky Differential Optical Absorption Spectroscopy (DOAS) measurements performe... more Ground-based zenith sky Differential Optical Absorption Spectroscopy (DOAS) measurements performed by means of GASCOD instruments at Mt. Cimone (44N 11E), Italy and Stara Zagora (42N, 25E), Bulgaria are used for validation of SCIAMACHY NO 2 vertical column density (vcd) of ESA SCI_NL product retrieved with 5.01 processor version. The results presented in this work regard satellite data for the July-December 2002 period. On this base it is concluded that during summer-autumn period the overall NO 2 vcd above both stations is fairly well reproduced by the SCIAMACHY data, while towards the winter period they deviate from the seasonal behaviour of NO 2 vcd derived at both stations.
Advances in Space Research, 2005
A correct interpretation of diffuse solar radiation measurements made by Differential Optical Abs... more A correct interpretation of diffuse solar radiation measurements made by Differential Optical Absorption Spectroscopy (DOAS) remote sensors require the use of radiative transfer models of the atmosphere. The simplest models consider radiation scattering in the atmosphere as a single scattering process. More realistic atmospheric models are those which consider multiple scattering and their application is useful and essential for the analysis of zenith and off-axis measurements regarding the lowest layers of the atmosphere, such as the boundary layer. These are characterized by the highest values of air density and quantities of particles and aerosols acting as scattering nuclei. A new atmospheric model, PROcessing of Multi-Scattered Atmospheric Radiation (PROMSAR), which includes multiple Rayleigh and Mie scattering, has recently been developed at ISAC-CNR. It is based on a backward Monte Carlo technique which is very suitable for studying the various interactions taking place in a complex and non-homogeneous system like the terrestrial atmosphere. PROMSAR code calculates the mean path of the radiation within each layer in which the atmosphere is subdivided taking into account the large variety of processes that solar radiation undergoes during propagation through the atmosphere. This quantity is then employed to work out the Air Mass Factor (AMF) of several trace gases, to simulate in zenith and off-axis configurations their slant column amounts and to calculate the weighting functions from which informations about the gas vertical distribution is obtained using inversion methods. Results from the model, simulations and comparisons with actual slant column measurements are presented and discussed.