Development of a microphysical model with a moment's representation for Titan's climate models

Les travaux présentés dans ce manuscrit porte sur le développement d’un modèle microphysique (aérosols et nuages) utilisant un schéma à deux moments. La méthode est développée dans le cas spécifique de Titan et a pour but l’intégration de modèles microphysiques sophistiqués dans les modèles climatiques (GCM). Le premier chapitre présente l’atmosphère du satellite de Saturne et plus particulièrement les aérosols la composant. Les deux chapitres suivant sont consacrés respectivement aux lois microphysiques (coagulation, sédimentation, nucléation et condensation) ainsi que l’adaptation de ces lois à la représentation en moments. Le quatrième chapitre est dédié à la modélisation de ce schéma à deux moments dans le cadre de la microphysique des nuages. Des comparaisons sur les principaux champs d’intérêt (opacité et température) sont effectués entre la représentation « classique » et la représentation en moments. Le dernier chapitre de cette thèse présente différentes études menées avec le Modèle de Climat Global (GCM) de Titan développé à l’IPSL.This thesis work is devoted to the development of a microphysics model (aerosols and clouds) using a two-moment scheme. The method is developed in the specific case of Titan and its final purpose is the integration of sophisticated microphysics models in climate models (GCM). The first chapter introduces the atmosphere of Saturn’s moon, and especially its aerosols. The next two chapters are devoted respectively to microphysical laws (coagulation, sedimentation, nucleation and condensation) and the adaptation of these laws to the moment scheme. The fourth chapter is dedicated to the modeling of this two-moment scheme for cloud microphysics. Comparisons on specific atmospheric fields (opacity and temperature) are mad between the “classical” scheme and the two-moment scheme. The final chapter of this thesis presents different studies with the Global Climate Model (GCM) of Titan developed at IPSL

Développement d'un modèle microphysique en moments pour les modèles climatiques de Titan

Les travaux présentés dans ce manuscrit porte sur le développement d un modèle microphysique (aérosols et nuages) utilisant un schéma à deux moments. La méthode est développée dans le cas spécifique de Titan et a pour but l intégration de modèles microphysiques sophistiqués dans les modèles climatiques (GCM). Le premier chapitre présente l atmosphère du satellite de Saturne et plus particulièrement les aérosols la composant. Les deux chapitres suivant sont consacrés respectivement aux lois microphysiques (coagulation, sédimentation, nucléation et condensation) ainsi que l adaptation de ces lois à la représentation en moments. Le quatrième chapitre est dédié à la modélisation de ce schéma à deux moments dans le cadre de la microphysique des nuages. Des comparaisons sur les principaux champs d intérêt (opacité et température) sont effectués entre la représentation classique et la représentation en moments. Le dernier chapitre de cette thèse présente différentes études menées avec le Modèle de Climat Global (GCM) de Titan développé à l IPSL.This thesis work is devoted to the development of a microphysics model (aerosols and clouds) using a two-moment scheme. The method is developed in the specific case of Titan and its final purpose is the integration of sophisticated microphysics models in climate models (GCM). The first chapter introduces the atmosphere of Saturn s moon, and especially its aerosols. The next two chapters are devoted respectively to microphysical laws (coagulation, sedimentation, nucleation and condensation) and the adaptation of these laws to the moment scheme. The fourth chapter is dedicated to the modeling of this two-moment scheme for cloud microphysics. Comparisons on specific atmospheric fields (opacity and temperature) are mad between the classical scheme and the two-moment scheme. The final chapter of this thesis presents different studies with the Global Climate Model (GCM) of Titan developed at IPSL.REIMS-SCD-Bib. electronique (514549901) / SudocSudocFranceF

Development of a new cloud model for Venus (MAD-VenLA) using the Modal Aerosol Dynamics approach

International audienceFor decades, clouds have remained a central open question in understanding the climate system of Venus. We have developed a new microphysical model for the clouds of Venus that we describe in this paper. The model is a modal aerosol dynamical model that treats the formation and evolution of sulfuric acid solution droplets with a moderate computational cost. To this end, the microphysical equations are derived to describe the evolution of the size distribution of the particles using the moments of the distribution. We describe the derivation of the equations and their implementation in the model. We tested each microphysical process of the model separately in conditions of the Venus’ atmosphere and show that the model behaves in a physically sound manner in the tested cases. The model will be coupled in the future with a Venus Global Climate Model and used for elucidating the remaining mysteries

On the cross-tropopause transport of water by tropical convective overshoots: a mesoscale modelling study constrained by in situ observations during the TRO-Pico field campaign in Brazil

International audienceDeep convection overshooting the lowermost stratosphere is well known for its role in the local stratospheric water vapour (WV) budget. While it is seldom the case, local enhancement of WV associated with stratospheric overshoots is often published. Nevertheless, one debatable topic persists regarding the global impact of this event with respect to the temperature-driven dehydration of air parcels entering the stratosphere. As a first step, it is critical to quantify their role at a cloud-resolving scale before assessing their impact on a large scale in a climate model. It would lead to a nudging scheme for large-scale simulation of overshoots.This paper reports on the local enhancements of WV linked to stratospheric overshoots, observed during the TRO-Pico campaign conducted in March 2012 in Bauru, Brazil, using the BRAMS (Brazilian version of the Regional Atmospheric Modeling System; RAMS) mesoscale model. Since numerical simulations depend on the choice of several preferred parameters, each having its uncertainties, we vary the microphysics or the vertical resolution while simulating the overshoots. Thus, we produce a set of simulations illustrating the possible variations in representing the stratospheric overshoots. To better resolve the stratospheric hydration, we opt for simulations with the 800 m horizontal-grid-point presentation. Next, we validate these simulations against the Bauru S-band radar echo tops and the TRO-Pico balloon-borne observations of WV and particles. Two of the three simulations’ setups yield results compatible with the TRO-Pico observations. From these two simulations, we determine approximately 333–2000 t of WV mass prevailing in the stratosphere due to an overshooting plume depending on the simulation setup. About 70 % of the ice mass remains between the 380 and 385 K isentropic levels. The overshooting top comprises pristine ice and snow, while aggregates only play a role just above the tropopause. Interestingly, the horizontal cross section of the overshooting top is about 450 km2 at the 380 K isentrope, which is similar to the horizontal-grid-point resolution of a simulation that cannot compute overshoots explicitly. In a large-scale simulation, these findings could provide guidance for a nudging scheme of overshooting hydration or dehydration

Microphysical modeling of the Venusian clouds with the IPSL Venus GCM

International audienceTo understand the Venus atmosphere, LMD and LATMOS laboratories have developed a 3D IPSL Venus Global Climate Model (Lebonnois et al. 2010). In this GCM, the cloud description is simplified. As clouds play a crucial role in radiative transfer, dynamics and generally the climate of Venus, it is necessary to improve the VGCM with a microphysical representation

A cloud modal representation for the IPSL Venus GCM: validation and first results

International audienceVenus is a terrestrial planet enshrouded by 20 km-thick clouds, which are composed of sulphuric acid-water solution droplets. To understand the Venus atmosphere, LMD and LATMOS laboratories have developed a 3D IPSL Venus Global Climate Model (Lebonnois et al. 2010). In this GCM, the cloud description is simplified. As clouds play a crucial role in radiative transfer, dynamics and generally the climate of Venus, it is necessary to improve the VGCM with a microphysical representation. To this end, we develop a Modal Aerosol Dynamics of Venusian Liquid Aerosol cloud model (MAD-VenLA). This model uses an implicit moment scheme to describe the particle size distribution and the microphysical processes in 0D. The particle size distribution is described by its first moments: total particle number (zeroth moment) and total particle volume (third moment) of the size distribution (Seigneur et al. 1986, Burgalat et al. 2014). Moreover, with this representation, the form of the size distribution is assumed to be a log-normal function. To represent a source of aerosol particles and the sedimentation of our cloud droplets, we have developed a 1D extension to our model. We are currently coupling MAD-VenLA with the 1D version of the IPSL Venus GCM.First, we will describe MAD-VenLA. Then, for validation, we will compare it with the sectional model SALSA in 0D (Kokkola et al. 2008), and with the CARMA Venus model (McGouldrick et al. 2007) and the Pioneer Venus LCPS observations (Knollenberg and Hunten, 1980) in 1D.In case of successful validation in 1D, we will be able to conduct 3D simulations with full microphysics in the future

The development of the Atmospheric Measurements by Ultra-Light Spectrometer (AMULSE) greenhouse gas profiling system and application for satellite retrieval validation

International audienceWe report in this paper the development of an embedded ultralight spectrometer (<3 kg) based on tuneable diode laser absorption spectroscopy (with a sampling rate of 24 Hz) in the mid-infrared spectral region. This instrument is dedicated to in situ measurements of the vertical profile concentrations of three main greenhouse gases – carbon dioxide (CO2), methane (CH4) and water vapour (H2O) – via standard weather and tethered balloons. The plug and play instrument is compact, robust, cost-effective, and autonomous. The instrument also has low power consumption and is non-intrusive.It was first calibrated during an in situ experiment on an ICOS (Integrated Carbon Observation System) site for several days, then used in two experiments with several balloon flights of up to 30 km altitude in the Reims region of France in 2017–2018 in collaboration with Météo-France CNRM (Centre National de Recherches Météorologiques).This paper shows the valuable interest of the data measured by the AMULSE (Atmospheric Measurements by Ultra-Light Spectrometer) instrument during the APOGEE (Atmospheric Profiles of Greenhouse Gases) measurement experiment, specifically for the vertical profiles of CO2 and CH4, measurements of which remain very sparse. We have carried out several experiments showing that the measured profiles have several applications: the validation of simulations of infrared satellite observations, evaluating the quality of chemical profiles from chemistry transport models (CTMs) and evaluating the quality of retrieved chemical profiles from the assimilation of infrared satellite observations. The results show that the simulations of infrared satellite observations from IASI (Infrared Atmospheric Sounding Interferometer) and CrIS (Cross-track Infrared Sounder) instruments performed in operational mode for numerical weather prediction (NWP) by the radiative transfer model (RTM) RTTOV (Radiative Transfer for the TIROS Operational Vertical Sounder) are of good quality. We also show that the MOCAGE (Modèle de Chimie Atmosphérique de Grande Echelle) and CAMS (Copernicus Atmospheric Monitoring Service) CTMs modelled ozone profiles fairly accurately and that the CAMS CTM represents the methane in the troposphere well compared to MOCAGE. Finally, the measured in situ ozone profiles allowed us to show the good quality of the retrieved ozone profiles by assimilating ozone-sensitive infrared spectral radiances from the IASI and CrIS

Dispersion des métaux de la mine au lagon : rôle du compartiment atmosphérique et dispersion au sein du compartiment biotique dulçaquicole et estuarien. Rapport scientifique final

- Ce rapport du programme DMML « Dispersion des métaux de la mine au lagon » constitue le volume 1 (sur 4) du programme intégré « Dispersion et exposition humaine aux métaux en Nouvelle-Calédonie » composé de 3 projets (DMML, Dynamine, Métexpo) étudiant les métaux et leur toxicité sur des sites pilotes similaires.- Le programme DMML a proposé de caractériser le potentiel de dispersion des éléments métalliques traces (ETM) Ni, Cr, Co et Mn au sein des compartiments abiotiques (atmosphère et pédosphère) et d’évaluer la contamination métallique dans le compartiment biotique de l’hydrosphère ainsi que de déterminer les mécanismes de transferts trophiques. - La caractérisation des flux d’ETM au sein de l’hydrosphère est réalisée dans le programme « Dynamine »

From microbiological to ecosystemic scale evaluation of carbon-based (CO2, CH4) greenhouse gas sources, production, and transfers in temperate peatlands: a pluridisciplinary week at the playground for Critical Zonists in Frasne, Jura Mountains

International audienceDespite covering only 3% of the global land surface, peatlands are an active part of the Critical Zone (CZ) exchanging large water and greenhouse gas (GHG) fluxes with the surrounding aquifers, surface waters, and the atmosphere. While ecosystem services of peatlands (carbon and water storage, buffering of local climate) are essential to address 21st century challenges regarding climate, biodiversity, and water resources, they are directly threatened by human activities at global (climate change) and local (drainage for agriculture, forestry and peat harvesting) scales. Understanding the hydrological, biogeochemical, and ecological mechanisms of peatlands functioning at different spatiotemporal scales is therefore fundamental to mitigate these impacts. In order to characterize the mechanisms and factors controlling GHG sources, production and transfers in peatlands, we organized an interdisciplinary field campaign at the Frasne peatland. The site (7 ha, 46.826 N, 6.1754E, 840 m a.s.l) is a long-term observatory since 2008 and one of the four French peatland observatories (SNO Tourbi`eres) of the French CZ research infrastructure (OZCAR). The peatland is also an observatory of the Zone Atelier of Arc Jurassien dedicated to exploring the interrelationships between human and nature.This campaign is supported by the TERRA FORMA project, aiming at designing and testing in-situ smart, connected, low-cost, low-impact and socially appropriated environmental sensors to capture the trajectory of the CZ in the Anthropocene. This field campaign will combine microbiological characterization (membrane lipid analysis to trace the involved microbial metabolisms) with hydrogeochemical analyses of peat pore water (major elements, DOC (quantity and quality), CO2, CH4, δ18OH2O-δ2HH2O, δ13CDIC, δ13CDOC, δ13CCH4, δ2HCH4, δ13CCO2) along upstream-downstream and surface-depth gradients. In parallel, GHG fluxes will be measured from the plot to the ecosystem scale, by combining dissolved gas profiles, chamber measurements, eddy-covariance and unmanned aerial vehicle characterization. This multiscale campaign will have the potential to address various challenges faced by Critical Zonists and environmental managers: (1) assessing 3D carbon fluxes (lateral and vertical) at the peatland scale; (2) characterizing biological processes and in particular how they favor or limit GHG production; (3) and transfers and developing affordable and user-friendly tools to face the above-mentioned topics