Emmanuel RIVIÈRE | Université de la Réunion (original) (raw)
Papers by Emmanuel RIVIÈRE
Modelling study of the impact of deep convection on the UTLS air
Journal of Atmospheric Chemistry, 2000
Two cases of simultaneous nighttime measurements of NO 2 and OClO in the winter polar stratospher... more Two cases of simultaneous nighttime measurements of NO 2 and OClO in the winter polar stratosphere are analyzed in order to test our present knowledge of halogen chemistry in the presence of high amount of NO 2 at low temperature. Comparisons with Lagrangian model calculations using several hypotheses are performed. First simulations, using the admitted constant rates of chemical reaction, strongly underestimate the measured OClO while the NO 2 profiles are correctly reproduced. If uncertainties in actinic fluxes calculations are taken into account, simulation results do not show a significant reduction of the underestimation. A better agreement can be achieved if the formation of unstable isomers of ClONO 2 and of BrONO 2 occurs in the cold conditions of the polar stratosphere. An approximate value of the branching ratios of the channels leading to ClONO 2 and ClOONO, and to BrONO 2 and BrOONO, necessary to reproduce both OClO and NO 2 is given and discussed.
Atmospheric Chemistry and Physics
The present paper is a preliminary study preparing the introduction of reversible trace gas uptak... more The present paper is a preliminary study preparing the introduction of reversible trace gas uptake by ice particles into a 3-D cloud resolving model. For this a 3-D simulation of a tropical deep convection cloud was run with the BRAMS cloud resolving model using a two-moment bulk microphysical parameterization. Trajectories within the convective clouds were computed from these simulation outputs along which the variations of the pristine ice, snow and aggregate mixing ratios and concentrations were extracted. The reversible uptake of 11 trace gases by ice was examined assuming applicability of Langmuir isotherms using recently evaluated (IUPAC) laboratory data. The results show that ice uptake is only significant for HNO3, HCl, CH3COOH and HCOOH. For H2O2, using new results for the partition coefficient results in significant partitioning to the ice phase for this trace gas also. It was also shown that the uptake is largely dependent on the temperature for some species. The adsorpti...
Icarus
Microphysical models describe the way aerosols and clouds behave in the atmosphere. Two approache... more Microphysical models describe the way aerosols and clouds behave in the atmosphere. Two approaches are generally used to model these processes. While the first approach discretizes processes and aerosols size distributions on a radius grid (bin scheme), the second uses bulk parameters of the size distribution law (its mathematical moments) to represent the evolution of the particle population (moment scheme). However, with the latter approach, one needs to have an a priori knowledge of the size distributions. Moments scheme for Cloud microphysics modeling have been used and enhanced since decades for climate studies of the Earth. Most of the tools are based on Log-Normal law which are suitable for Earth, Mars or Venus. On Titan, due to the fractal structure of the aerosols, the size distributions do not follow a log-normal law. Then using a moment scheme in that case implies to define the description of the size distribution and to review the equations that are widely published in t...
ATMOSPHERIC CHEMISTRY AND PHYSICS
The general objective of this series of papers is to evaluate long duration limited area simulati... more The general objective of this series of papers is to evaluate long duration limited area simulations with idealised tracers as a tool to assess tracer transport in chemistry-transport models (CTMs). In this first paper, we analyse the results of six simulations using different convection closures and parameterizations. The simulations are using the Grell and Dévényi (2002) mass-flux framework for the convection parameterization with different closures (Grell = GR, Arakawa-Shubert = AS, Kain-Fritch = KF, Low omega = LO, Moisture convergence = MC) and an ensemble parameterization (EN) based on the other five closures. The simulations are run for one month during the SCOUT-O3 field campaign lead from Darwin (Australia). They have a 60 km horizontal resolution and a fine vertical resolution in the upper troposphere/lower stratosphere. Meteorological results are compared with satellite products, radiosoundings and SCOUT-O3 aircraft campaign data. They show that the model is generally in ...
Atmospheric Chemistry and Physics
The aim of this paper is to study the impacts of overshooting convection at a local scale on the ... more The aim of this paper is to study the impacts of overshooting convection at a local scale on the water distribution in the tropical UTLS. Overshooting convection is likely to be one of the key processes controlling the entry of water vapour amount in the stratosphere by injecting ice crystals above the tropopause which later sublimate and hydrate the lower stratosphere. For this purpose, we quantify the individual impact of two overshooting cases in Africa observed during SCOUT-AMMA: the case of 4 August 2006 over Southern Chad which is likely to have influenced the water vapour measurements by micro-SDLA and FLASH-B from Niamey on 5 August, and the case of a mesoscale convective system over Aϊr on 5 August 2006. We make use of high resolution (down to 1 km horizontally) three nested grid simulations with the three-dimensional regional atmospheric model BRAMS (Brazilian Regional Atmospheric Modelling System). In both cases, BRAMS succeeds in simulating the main features of the conve...
We present the results of accurate balloon-borne observations of water vapor and aerosol obtained... more We present the results of accurate balloon-borne observations of water vapor and aerosol obtained during a field campaign held in March 2012 in Bauru, Brazil (22.3 S) in the frame of a TRO-pico project. The aim of the TRO-pico project, supported by the French ANR, is to characterize the variability and frequency of water convective injections, their contribution at the regional wet season timescale, and to improve the understanding of their role with respect to the cold trap at a wider scale. The balloon payloads flown during the campaign included Pico-SDLA IR laser hygrometers, FLASH-B fluorescence Lyman-alpha hygrometers, COBALD aerosol backscatter sondes and several other instruments for the measurement of gas-phase and particle constituents. A S-band radar operating on the site provided the information on cloud tops. The series of vertical profiles obtained show well correlated enhancements in water vapor and aerosol in the lowermost stratosphere at 430 K in some of the sounding...
Le nouveau programme ADOMOCA-3 a été accepté pour une année seulement par le LEFE en mettant en a... more Le nouveau programme ADOMOCA-3 a été accepté pour une année seulement par le LEFE en mettant en avant l'importance des réunions annuelles permettant de présenter et de discuter les avancées opérées dans chaque laboratoire tant sur les plans technique que scientifique ainsi que la lettre trimestrielle ACHILLE. Nous élargissons la communauté à d'autres équipes au sein de laboratoires identifiés précédemment, soit une trentaine de chercheurs. Nous souhaitons définir des axes de recherche prioritaire qui vont nous permettre de bâtir une proposition d'envergure nationale (e.g. ANR) et/ou internationale (e.g. H2020) afin de financer prioritairement des ressources humaines (thèses et post-docs). Le plan de recherche est ventilé en quatre thèmes : 1) aérosols, 2) composition gazeuse, 3) inversion de sources et estimations des paramètres et 4) méthodologie. Parmi ces 4 thématiques, certaines actions sont déjà structurées comme des projets collaboratifs autour de questions bien identifiées. D'autres, au contraire, sont présentées sous la forme d'actions propres à chaque laboratoire et, dans ce cas, ADOMOCA-3 doit servir à enclencher la synergie entre les différentes équipes.
ATMOSPHERIC CHEMISTRY AND PHYSICS
The aim of this paper is to study the impacts of overshooting convection at a local scale on the ... more The aim of this paper is to study the impacts of overshooting convection at a local scale on the water distribution in the tropical UTLS. Overshooting convection is assumed to be one of the processes controlling the entry of water vapour mixing ratio in the stratosphere by injecting ice crystals above the tropopause which later sublimate and hydrate the lower stratosphere. For this purpose, we quantify the individual impact of two cases of overshooting convection in Africa observed during SCOUT-AMMA: the case of 4 August 2006 over Southern Chad which is likely to have influenced the water vapour measurements by micro-SDLA and FLASH-B from Niamey on 5 August, and the case of a mesoscale convective system over Aïr on 5 August 2006. We make use of high resolution (down to 1 km horizontally) nested grid simulations with the three-dimensional regional atmospheric model BRAMS (Brazilian Regional Atmospheric Modelling System). In both cases, BRAMS succeeds in simulating the main features o...
Tropical deep convection plays an important role in the upper troposphere/lower stratosphere chem... more Tropical deep convection plays an important role in the upper troposphere/lower stratosphere chemical composition. It is known that the species emitted in the planetary boundary layer are carried into the upper troposphere by deep convection from which part of them, then, reach the lower stratosphere by large scale transport. A concurrent pathway to the lower stratosphere is via the most intense deep convection, called "overshooting" convection, which is able to directly inject tropospheric air in the stratospheric overworld, as was illustrated by ice particles at 420 K observed during EU FP7 project SCOUT-O3. However, the detailed processes leading to troposphere-to-stratosphere transport (TST) and their quantification are still debated. The large scale processes are generally well handled by global Chemistry Transport Models (CTMs) which are forced by dynamical fields from state-of-art weather forecast models. In most current CTMs the subgrid-scale convection is paramete...
Thunderstorms over tropical continents have been shown recently to have a large impact on the the... more Thunderstorms over tropical continents have been shown recently to have a large impact on the thermal structure, the chemical composition, the humidity and the aerosol concentration of the lower stratosphere well above the tropopause up to 20-21 km altitude. The reason for the ignorance of this mechanism until now is the difficulty of performing relevant observations from satellites and high altitude research aircraft, in the presence of strong overshoots at vertical velocity up to 60m/s, permanent lightning and cold temperature associated to those systems, as well as performing large balloons flights next to heavy rainfall and wind gusts. An alternative is to probe the upper troposphere and the lower stratosphere using small balloons flown next to the thunderstorms or long duration balloons passing above, carrying lightweight and high performance sensors now feasible using modern technics. In this objective, several lightweight instruments have been developed which will be flown in...
Journal of Geophysical Research Atmospheres
1] Signatures of nitric acid particles (NAP) in cold thick ice clouds have been derived from sate... more 1] Signatures of nitric acid particles (NAP) in cold thick ice clouds have been derived from satellite observations. Most NAP are detected in the tropics (9 to 20% of clouds with T < 202.5 K). Higher occurrences were found in the rare midlatitudes very cold clouds. NAP occurrence increases as cloud temperature decreases, and NAP are more numerous in January than July. Comparisons of NAP and lightning distributions show that lightning seems to be the main source of the NO x , which forms NAP in cold clouds over continents. Qualitative comparisons of NAP with upper tropospheric humidity distributions suggest that NAP may play a role in the dehydration of the upper troposphere when the tropopause is colder than 195 K.re (2007), Nitric acid particles in cold thick ice clouds observed at global scale: Link with lightning, temperature, and upper tropospheric water vapor, J. Geophys. Res., 112, D05212, doi:10.1029/2005JD006602.
ATMOSPHERIC CHEMISTRY AND PHYSICS
The general objective of this series of two papers is to evaluate long duration limited-area simu... more The general objective of this series of two papers is to evaluate long duration limited-area simulations with idealised tracers as a possible tool to assess the tracer transport in chemistry-transport models (CTMs). In this second paper we analyse the results of three simulations using different horizontal and vertical resolutions. The goal is to study the impact of the model spatial resolution on convective transport of idealized tracer in the tropics. The reference simulation (REF) uses a 60 km horizontal resolution and 300 m vertically in the upper troposphere/lower stratosphere (UTLS). A 20 km horizontal resolution simulation (HR) is run as well as a simulation with 850 m vertical resolution in the UTLS (CVR). The simulations are run for one month during the SCOUT-O3 field campaign. Aircraft data, TRMM rainrate estimates and radiosoundings have been used to evaluate the simulations. They show that the HR configuration gives generally a better agreement with the measurements than...
Atmospheric Chemistry and Physics
In this study, we evaluate the ability of the BRAMS (Brazilian Regional Atmospheric Modeling Syst... more In this study, we evaluate the ability of the BRAMS (Brazilian Regional Atmospheric Modeling System) mesoscale model compared to ECMWF global analysis to simulate the observed vertical variations of water vapour in the tropical upper troposphere and lower stratosphere (UTLS). The observations are balloon-borne measurements of water vapour mixing ratio and temperature from micro-SDLA (Tunable Diode Laser Spectrometer) instrument. Data from two balloon flights performed during the 2004 HIBISCUS field campaign are used to compare with the mesoscale simulations and to the ECMWF analysis. The observations exhibit fine scale vertical structures of water vapour of a few hundred meters height. The ECMWF vertical resolution (~1 km) is too coarse to capture these vertical structures in the UTLS. With a vertical resolution similar to ECMWF, the mesoscale model performs better than ECMWF analysis for water vapour in the upper troposphere and similarly or slightly worse for temperature. The BRAM...
Applied Physics B
We report the development of a laser sonde operated under stratospheric balloons and devoted to t... more We report the development of a laser sonde operated under stratospheric balloons and devoted to the in-situ measurement of carbon dioxide in the upper troposphere and the lower stratosphere. In the 2.68 micron region, strong CO2 transitions are suitable for the in-situ monitoring of carbon dioxide, which gives ∼10% absorption depth and, moreover, antimonide laser diodes are nowadays available that show relevant spectral properties for absorption spectroscopy. The light-weight sensor is based on 50-cm single path configuration and is operated open to the atmosphere. We provide details of the design of the instrument and data processing. The performance and the stability of the instrument were evaluated with the Allan variance technique. The spectrometer was test-flown in the Arctic stratosphere from Kiruna, Sweden and we report preliminary flight results.
Following water vapor and carbon dioxide, methane is the most important greenhouse gas in the Ear... more Following water vapor and carbon dioxide, methane is the most important greenhouse gas in the Earth atmosphere. On a per molecule basis, methane is much more radiatively efficient than carbon dioxide [1]. The concentration of methane in the atmosphere has dramatically increased since the pre-industrial area. The increase of methane concentration in the atmosphere is of major interest because of it is impact on the radiative balance of the Earth and the atmospheric chemistry. Methane is released into the atmosphere by several sources, both anthropogenic and natural. It is suspected that global warming can induced additional methane release in the atmosphere by permafrost degradation. Moreover, methane is an interesting atmospheric tracer in order to study the impact of the deep convection on the tropical lower stratosphere. In the stratosphere, methane is a source of water vapour by oxidation [2, 3, 4], and consequently play a role in the budget of stratospheric water vapor. With the...
Journal of Geophysical Research, 2003
Denitrification is well known to affect the severity of springtime ozone depletion in Polar Regio... more Denitrification is well known to affect the severity of springtime ozone depletion in Polar Regions. In winter 1996/1997 in the Northern Hemisphere and winter 1997 in the Southern Hemisphere, the Improved Limb Atmospheric Spectrometer (ILAS) on board the Advanced Earth Observing Satellite (ADEOS) detected denitrification in both hemispheres. Here the Match technique and a Lagrangian model are used to analyze
Journal of Geophysical Research, 2003
Journal of Atmospheric Chemistry, 2005
Eleven vertical profiles of stratospheric NO 3 have been obtained since 1992 using the AMON and S... more Eleven vertical profiles of stratospheric NO 3 have been obtained since 1992 using the AMON and SALOMON balloon-borne UV-visible spectrometers. The measurements are compared to the SLIMCAT 3D model and calculations based on the steady-state hypothesis for NO 3 . The calculations cannot reproduce some parts of the profiles which exhibit strong concentration fluctuations over few kilometres, as a consequence of the dependence of NO 3 on local temperature variations. A statistical use of the data allows us to estimate the influence of the temperature dependence of the absorption cross-section on the data analysis, and the validity of the recommended reaction rates available in the literature. Discrepancies exist between the model based on recommended kinetics and observations at warmer temperatures. Nevertheless, the analysis is biased by local temperature inhomogeneities, and only a low-resolution vertical shape of the NO 3 profiles can be retrieved.
Modelling study of the impact of deep convection on the UTLS air
Journal of Atmospheric Chemistry, 2000
Two cases of simultaneous nighttime measurements of NO 2 and OClO in the winter polar stratospher... more Two cases of simultaneous nighttime measurements of NO 2 and OClO in the winter polar stratosphere are analyzed in order to test our present knowledge of halogen chemistry in the presence of high amount of NO 2 at low temperature. Comparisons with Lagrangian model calculations using several hypotheses are performed. First simulations, using the admitted constant rates of chemical reaction, strongly underestimate the measured OClO while the NO 2 profiles are correctly reproduced. If uncertainties in actinic fluxes calculations are taken into account, simulation results do not show a significant reduction of the underestimation. A better agreement can be achieved if the formation of unstable isomers of ClONO 2 and of BrONO 2 occurs in the cold conditions of the polar stratosphere. An approximate value of the branching ratios of the channels leading to ClONO 2 and ClOONO, and to BrONO 2 and BrOONO, necessary to reproduce both OClO and NO 2 is given and discussed.
Atmospheric Chemistry and Physics
The present paper is a preliminary study preparing the introduction of reversible trace gas uptak... more The present paper is a preliminary study preparing the introduction of reversible trace gas uptake by ice particles into a 3-D cloud resolving model. For this a 3-D simulation of a tropical deep convection cloud was run with the BRAMS cloud resolving model using a two-moment bulk microphysical parameterization. Trajectories within the convective clouds were computed from these simulation outputs along which the variations of the pristine ice, snow and aggregate mixing ratios and concentrations were extracted. The reversible uptake of 11 trace gases by ice was examined assuming applicability of Langmuir isotherms using recently evaluated (IUPAC) laboratory data. The results show that ice uptake is only significant for HNO3, HCl, CH3COOH and HCOOH. For H2O2, using new results for the partition coefficient results in significant partitioning to the ice phase for this trace gas also. It was also shown that the uptake is largely dependent on the temperature for some species. The adsorpti...
Icarus
Microphysical models describe the way aerosols and clouds behave in the atmosphere. Two approache... more Microphysical models describe the way aerosols and clouds behave in the atmosphere. Two approaches are generally used to model these processes. While the first approach discretizes processes and aerosols size distributions on a radius grid (bin scheme), the second uses bulk parameters of the size distribution law (its mathematical moments) to represent the evolution of the particle population (moment scheme). However, with the latter approach, one needs to have an a priori knowledge of the size distributions. Moments scheme for Cloud microphysics modeling have been used and enhanced since decades for climate studies of the Earth. Most of the tools are based on Log-Normal law which are suitable for Earth, Mars or Venus. On Titan, due to the fractal structure of the aerosols, the size distributions do not follow a log-normal law. Then using a moment scheme in that case implies to define the description of the size distribution and to review the equations that are widely published in t...
ATMOSPHERIC CHEMISTRY AND PHYSICS
The general objective of this series of papers is to evaluate long duration limited area simulati... more The general objective of this series of papers is to evaluate long duration limited area simulations with idealised tracers as a tool to assess tracer transport in chemistry-transport models (CTMs). In this first paper, we analyse the results of six simulations using different convection closures and parameterizations. The simulations are using the Grell and Dévényi (2002) mass-flux framework for the convection parameterization with different closures (Grell = GR, Arakawa-Shubert = AS, Kain-Fritch = KF, Low omega = LO, Moisture convergence = MC) and an ensemble parameterization (EN) based on the other five closures. The simulations are run for one month during the SCOUT-O3 field campaign lead from Darwin (Australia). They have a 60 km horizontal resolution and a fine vertical resolution in the upper troposphere/lower stratosphere. Meteorological results are compared with satellite products, radiosoundings and SCOUT-O3 aircraft campaign data. They show that the model is generally in ...
Atmospheric Chemistry and Physics
The aim of this paper is to study the impacts of overshooting convection at a local scale on the ... more The aim of this paper is to study the impacts of overshooting convection at a local scale on the water distribution in the tropical UTLS. Overshooting convection is likely to be one of the key processes controlling the entry of water vapour amount in the stratosphere by injecting ice crystals above the tropopause which later sublimate and hydrate the lower stratosphere. For this purpose, we quantify the individual impact of two overshooting cases in Africa observed during SCOUT-AMMA: the case of 4 August 2006 over Southern Chad which is likely to have influenced the water vapour measurements by micro-SDLA and FLASH-B from Niamey on 5 August, and the case of a mesoscale convective system over Aϊr on 5 August 2006. We make use of high resolution (down to 1 km horizontally) three nested grid simulations with the three-dimensional regional atmospheric model BRAMS (Brazilian Regional Atmospheric Modelling System). In both cases, BRAMS succeeds in simulating the main features of the conve...
We present the results of accurate balloon-borne observations of water vapor and aerosol obtained... more We present the results of accurate balloon-borne observations of water vapor and aerosol obtained during a field campaign held in March 2012 in Bauru, Brazil (22.3 S) in the frame of a TRO-pico project. The aim of the TRO-pico project, supported by the French ANR, is to characterize the variability and frequency of water convective injections, their contribution at the regional wet season timescale, and to improve the understanding of their role with respect to the cold trap at a wider scale. The balloon payloads flown during the campaign included Pico-SDLA IR laser hygrometers, FLASH-B fluorescence Lyman-alpha hygrometers, COBALD aerosol backscatter sondes and several other instruments for the measurement of gas-phase and particle constituents. A S-band radar operating on the site provided the information on cloud tops. The series of vertical profiles obtained show well correlated enhancements in water vapor and aerosol in the lowermost stratosphere at 430 K in some of the sounding...
Le nouveau programme ADOMOCA-3 a été accepté pour une année seulement par le LEFE en mettant en a... more Le nouveau programme ADOMOCA-3 a été accepté pour une année seulement par le LEFE en mettant en avant l'importance des réunions annuelles permettant de présenter et de discuter les avancées opérées dans chaque laboratoire tant sur les plans technique que scientifique ainsi que la lettre trimestrielle ACHILLE. Nous élargissons la communauté à d'autres équipes au sein de laboratoires identifiés précédemment, soit une trentaine de chercheurs. Nous souhaitons définir des axes de recherche prioritaire qui vont nous permettre de bâtir une proposition d'envergure nationale (e.g. ANR) et/ou internationale (e.g. H2020) afin de financer prioritairement des ressources humaines (thèses et post-docs). Le plan de recherche est ventilé en quatre thèmes : 1) aérosols, 2) composition gazeuse, 3) inversion de sources et estimations des paramètres et 4) méthodologie. Parmi ces 4 thématiques, certaines actions sont déjà structurées comme des projets collaboratifs autour de questions bien identifiées. D'autres, au contraire, sont présentées sous la forme d'actions propres à chaque laboratoire et, dans ce cas, ADOMOCA-3 doit servir à enclencher la synergie entre les différentes équipes.
ATMOSPHERIC CHEMISTRY AND PHYSICS
The aim of this paper is to study the impacts of overshooting convection at a local scale on the ... more The aim of this paper is to study the impacts of overshooting convection at a local scale on the water distribution in the tropical UTLS. Overshooting convection is assumed to be one of the processes controlling the entry of water vapour mixing ratio in the stratosphere by injecting ice crystals above the tropopause which later sublimate and hydrate the lower stratosphere. For this purpose, we quantify the individual impact of two cases of overshooting convection in Africa observed during SCOUT-AMMA: the case of 4 August 2006 over Southern Chad which is likely to have influenced the water vapour measurements by micro-SDLA and FLASH-B from Niamey on 5 August, and the case of a mesoscale convective system over Aïr on 5 August 2006. We make use of high resolution (down to 1 km horizontally) nested grid simulations with the three-dimensional regional atmospheric model BRAMS (Brazilian Regional Atmospheric Modelling System). In both cases, BRAMS succeeds in simulating the main features o...
Tropical deep convection plays an important role in the upper troposphere/lower stratosphere chem... more Tropical deep convection plays an important role in the upper troposphere/lower stratosphere chemical composition. It is known that the species emitted in the planetary boundary layer are carried into the upper troposphere by deep convection from which part of them, then, reach the lower stratosphere by large scale transport. A concurrent pathway to the lower stratosphere is via the most intense deep convection, called "overshooting" convection, which is able to directly inject tropospheric air in the stratospheric overworld, as was illustrated by ice particles at 420 K observed during EU FP7 project SCOUT-O3. However, the detailed processes leading to troposphere-to-stratosphere transport (TST) and their quantification are still debated. The large scale processes are generally well handled by global Chemistry Transport Models (CTMs) which are forced by dynamical fields from state-of-art weather forecast models. In most current CTMs the subgrid-scale convection is paramete...
Thunderstorms over tropical continents have been shown recently to have a large impact on the the... more Thunderstorms over tropical continents have been shown recently to have a large impact on the thermal structure, the chemical composition, the humidity and the aerosol concentration of the lower stratosphere well above the tropopause up to 20-21 km altitude. The reason for the ignorance of this mechanism until now is the difficulty of performing relevant observations from satellites and high altitude research aircraft, in the presence of strong overshoots at vertical velocity up to 60m/s, permanent lightning and cold temperature associated to those systems, as well as performing large balloons flights next to heavy rainfall and wind gusts. An alternative is to probe the upper troposphere and the lower stratosphere using small balloons flown next to the thunderstorms or long duration balloons passing above, carrying lightweight and high performance sensors now feasible using modern technics. In this objective, several lightweight instruments have been developed which will be flown in...
Journal of Geophysical Research Atmospheres
1] Signatures of nitric acid particles (NAP) in cold thick ice clouds have been derived from sate... more 1] Signatures of nitric acid particles (NAP) in cold thick ice clouds have been derived from satellite observations. Most NAP are detected in the tropics (9 to 20% of clouds with T < 202.5 K). Higher occurrences were found in the rare midlatitudes very cold clouds. NAP occurrence increases as cloud temperature decreases, and NAP are more numerous in January than July. Comparisons of NAP and lightning distributions show that lightning seems to be the main source of the NO x , which forms NAP in cold clouds over continents. Qualitative comparisons of NAP with upper tropospheric humidity distributions suggest that NAP may play a role in the dehydration of the upper troposphere when the tropopause is colder than 195 K.re (2007), Nitric acid particles in cold thick ice clouds observed at global scale: Link with lightning, temperature, and upper tropospheric water vapor, J. Geophys. Res., 112, D05212, doi:10.1029/2005JD006602.
ATMOSPHERIC CHEMISTRY AND PHYSICS
The general objective of this series of two papers is to evaluate long duration limited-area simu... more The general objective of this series of two papers is to evaluate long duration limited-area simulations with idealised tracers as a possible tool to assess the tracer transport in chemistry-transport models (CTMs). In this second paper we analyse the results of three simulations using different horizontal and vertical resolutions. The goal is to study the impact of the model spatial resolution on convective transport of idealized tracer in the tropics. The reference simulation (REF) uses a 60 km horizontal resolution and 300 m vertically in the upper troposphere/lower stratosphere (UTLS). A 20 km horizontal resolution simulation (HR) is run as well as a simulation with 850 m vertical resolution in the UTLS (CVR). The simulations are run for one month during the SCOUT-O3 field campaign. Aircraft data, TRMM rainrate estimates and radiosoundings have been used to evaluate the simulations. They show that the HR configuration gives generally a better agreement with the measurements than...
Atmospheric Chemistry and Physics
In this study, we evaluate the ability of the BRAMS (Brazilian Regional Atmospheric Modeling Syst... more In this study, we evaluate the ability of the BRAMS (Brazilian Regional Atmospheric Modeling System) mesoscale model compared to ECMWF global analysis to simulate the observed vertical variations of water vapour in the tropical upper troposphere and lower stratosphere (UTLS). The observations are balloon-borne measurements of water vapour mixing ratio and temperature from micro-SDLA (Tunable Diode Laser Spectrometer) instrument. Data from two balloon flights performed during the 2004 HIBISCUS field campaign are used to compare with the mesoscale simulations and to the ECMWF analysis. The observations exhibit fine scale vertical structures of water vapour of a few hundred meters height. The ECMWF vertical resolution (~1 km) is too coarse to capture these vertical structures in the UTLS. With a vertical resolution similar to ECMWF, the mesoscale model performs better than ECMWF analysis for water vapour in the upper troposphere and similarly or slightly worse for temperature. The BRAM...
Applied Physics B
We report the development of a laser sonde operated under stratospheric balloons and devoted to t... more We report the development of a laser sonde operated under stratospheric balloons and devoted to the in-situ measurement of carbon dioxide in the upper troposphere and the lower stratosphere. In the 2.68 micron region, strong CO2 transitions are suitable for the in-situ monitoring of carbon dioxide, which gives ∼10% absorption depth and, moreover, antimonide laser diodes are nowadays available that show relevant spectral properties for absorption spectroscopy. The light-weight sensor is based on 50-cm single path configuration and is operated open to the atmosphere. We provide details of the design of the instrument and data processing. The performance and the stability of the instrument were evaluated with the Allan variance technique. The spectrometer was test-flown in the Arctic stratosphere from Kiruna, Sweden and we report preliminary flight results.
Following water vapor and carbon dioxide, methane is the most important greenhouse gas in the Ear... more Following water vapor and carbon dioxide, methane is the most important greenhouse gas in the Earth atmosphere. On a per molecule basis, methane is much more radiatively efficient than carbon dioxide [1]. The concentration of methane in the atmosphere has dramatically increased since the pre-industrial area. The increase of methane concentration in the atmosphere is of major interest because of it is impact on the radiative balance of the Earth and the atmospheric chemistry. Methane is released into the atmosphere by several sources, both anthropogenic and natural. It is suspected that global warming can induced additional methane release in the atmosphere by permafrost degradation. Moreover, methane is an interesting atmospheric tracer in order to study the impact of the deep convection on the tropical lower stratosphere. In the stratosphere, methane is a source of water vapour by oxidation [2, 3, 4], and consequently play a role in the budget of stratospheric water vapor. With the...
Journal of Geophysical Research, 2003
Denitrification is well known to affect the severity of springtime ozone depletion in Polar Regio... more Denitrification is well known to affect the severity of springtime ozone depletion in Polar Regions. In winter 1996/1997 in the Northern Hemisphere and winter 1997 in the Southern Hemisphere, the Improved Limb Atmospheric Spectrometer (ILAS) on board the Advanced Earth Observing Satellite (ADEOS) detected denitrification in both hemispheres. Here the Match technique and a Lagrangian model are used to analyze
Journal of Geophysical Research, 2003
Journal of Atmospheric Chemistry, 2005
Eleven vertical profiles of stratospheric NO 3 have been obtained since 1992 using the AMON and S... more Eleven vertical profiles of stratospheric NO 3 have been obtained since 1992 using the AMON and SALOMON balloon-borne UV-visible spectrometers. The measurements are compared to the SLIMCAT 3D model and calculations based on the steady-state hypothesis for NO 3 . The calculations cannot reproduce some parts of the profiles which exhibit strong concentration fluctuations over few kilometres, as a consequence of the dependence of NO 3 on local temperature variations. A statistical use of the data allows us to estimate the influence of the temperature dependence of the absorption cross-section on the data analysis, and the validity of the recommended reaction rates available in the literature. Discrepancies exist between the model based on recommended kinetics and observations at warmer temperatures. Nevertheless, the analysis is biased by local temperature inhomogeneities, and only a low-resolution vertical shape of the NO 3 profiles can be retrieved.