Impact of clouds parameterization on warm conveyor belts and jet-stream dynamics. A modeling and observational approach

14/02/2022 11:00

« Climat : comprendre, s'éduquer, agir »

10/02/2022 00:00

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02/02/2022 18:00

Physical and biogeochemical responses to the GEOMETRIC eddy parameterisation in an idealised ocean model

06/11/2023 11:00

Séminaire du LOCEAN

ClimSnow : genèse, déploiement et enjeux d’un service climatique sectoriel original pour l’adaptation au changement climatique du tourisme hivernal en stations de montagne

27/10/2023 11:00

Samuel Morin est chercheur et directeur du CNRM (UMR Météo-France – CNRS).

A biological oceanographer's perspective on understanding future ocean states

24/10/2023 11:00

Séminaire du LOCEAN

Towards a combined NDACC/TCCON site at Paris for integrated climate and air quality studies above a European megacity

18/09/2025 14:00

The European megacity of Paris, with its 11 million inhabitants, offers a unique platform for the study of atmospheric composition and air quality. Since 2007, we have been using a high spectral resolution Fourier Transform Spectrometer (FTS-Paris) to monitor the composition of the atmosphere over Paris. Measurement configurations can be switched between near-infrared observations for the Total Carbon Column Observing Network (TCCON), of which FTS-Paris has been an official member since 2014, and thermal infrared observations within the frame of the Network for the Detection of Atmospheric Composition Change Infrared Working Group (NDACC-IRWG).

The main objective of this thesis work is to qualify the Paris site as a new NDACC-IRWG measurement station in a European megacity. It was thus necessary to implement NDACC-IRWG recommended retrieval strategies for analysing the atmospheric spectra recorded by the FTS-Paris instrument. The retrieval of atmospheric trace gas abundances had also to comply with the specifications imposed by the NDACC-IRWG network. We present these inversion strategies with the SFIT4 radiative transfer code, as well as long time series of total columns of NDACC-IRWG standard products (CO, C₂H₆, HCl, N₂O, CH₄, HF and HCN) and non-standard products (H₂CO, NO₂ and OCS). These results have allowed the Paris site to join the NDACC network in 2024.

In addition to the long-term climatology of the NDACC products, an analysis of 10 years of back-trajectories from the HYSPLITT model was carried out and used to describe the wind patterns (direction, frequence) at Paris in order to characterise the site at Jussieu. These back trajectories help to understand observed variations of de-seasonalized total columns of carbon monoxide (ΔCO) and ethane (ΔC₂H₆). Episodes with extreme ΔCO and ΔC₂H₆ values, corresponding to clean and polluted air masses, are analysed and discussed. Using simple kinetic modelling, we compare the seasonal variations of the ratio between CO and C₂H₆ total columns to the corresponding emission ratio.

Diversification chimique des aérosols organiques en chimie prébiotique: incorporation de soufre et d'oxygène dans les aérosols photochimiques organiques

10/10/2025 14:00

Le vivant se compose d’une diversité d’éléments chimiques, les C, H, N, O, P, S, qui définissent sa structure organique à l’échelle moléculaire. Néanmoins l’origine de cette composition organique complexe et de l’incorporation des hétéro-éléments N, O, P, S demeure à ce jour énigmatique. Pour y répondre, la caractérisation des réservoirs organiques primitifs est indispensable afin de mettre en lumière la transition de l’organique abiotique à l’organique biologique.

Parmi ces réservoirs primordiaux, source de matière organique, l’atmosphère de la Terre primitive hadéenne a pu jouer un rôle prépondérant via la photochimie. L’exploration du système solaire au cours des dernières décennies a contribué à montrer que la chimie atmosphérique pouvait être une source de matière organique complexe.

L’étude de Titan et de son atmosphère dense par la mission Cassini (2004-2017) a notamment révélé l’existence d’une chimie avancée conduisant, à partir de ses principaux volatiles N₂ et CH₄, à la formation d’aérosols (particules solides) organiques. Les observations de Cassini couplées aux expériences de  laboratoire reproduisant  la chimie atmosphérique de Titan ont mis en évidence la complexité moléculaire de ces aérosols ainsi que leur forte teneur en azote. La caractérisation de la structure de ces aérosols a également apporté des contraintes sur leurs mécanismes de formation, mettant en avant certaines voies réactionnelles de complexification organique potentiellement actives dans l’atmosphère primitive.
Néanmoins la photochimie de l’atmosphère primitive ne peut se restreindre à celle de l’atmosphère de Titan. Si la composition de l’atmosphère primitive hadéenne n’est pas contrainte à ce jour, il est très vraisemblable que celle-ci ait significativement différé de celle de Titan.

L’atmosphère primitive a notamment pu accueillir une plus grande diversité d’éléments chimiques à savoir le carbone, l’hydrogène, l’azote, mais aussi l’oxygène et le soufre. Ces deux derniers éléments ont pu être émis en quantité significative dans l’atmosphère principalement via l’activité volcanique et le dégazage magmatique supposés particulièrement intenses à l’hadéen.

Dans cette thèse nous avons cherché à approcher le fruit de cette photochimie hadéenne chimiquement diversifiée en produisant et caractérisant des aérosols organiques intégrant l’ensemble de ces éléments chimiques C, H, N, O, S. Cette démarche vise à mettre en lumière de nouveaux composés organiques et de nouvelles voies réactionnelles pour comprendre la chimie des origines.

Pour former ces aérosols chimiquement diversifiés, nous nous sommes appuyés sur une matrice organique complexe, bien caractérisée et riche en carbone, azote et hydrogène : les analogues d’aérosols de Titan, également appelés tholins. Nous avons exploré des conditions propices à l’incorporation d’oxygène et de soufre au sein de cette matrice. La caractérisation des aérosols organiques ainsi produits a révélé la formation de nouveaux composés organiques oxydés et organo-soufrés. Parmi cette diversité de nouvelles fonctions chimiques, on identifie principalement, pour le soufre, des thiocyanates (RSCN) et des isothiocyanates (RNCS), et pour l’oxygène, de l’urée ainsi que des dérivés d’acides carboxyliques. Les mécanismes de formation de ces composés sont dominés par des processus hétérogènes se déroulant à la surface des grains.

The radiative effects of absorbing aerosols

19/09/2025 14:30

Atmospheric aerosols are a key component of the climate system and major contributors to the Earth’s radiation budget. Understanding the role of aerosols in the radiative transfer of solar and infrared radiation in the atmosphere is crucial to understand their implication in past, present and future climate and climate changes. Currently, knowledge of the climatic properties of aerosols and their variability in link to varying emission sources and atmospheric ageing remains limited, particularly for natural and anthropogenic absorbing species such as mineral dust and carbonaceous aerosols containing black carbon (BC) and brown carbon (BrC). As a matter of fact, the spectral optical properties of aerosols, governing their direct interaction with radiation (scattering and absorption), as well as their ability to act as condensation nuclei for liquid (CCN) and ice (IN) clouds, are still largely unknown. Consequently, the representation of absorbing aerosols in climate models and satellite retrieval algorithms remains inadequate, which severely limits the ability to constrain their role in the radiation budget and its implications for regional and global climate.

My research activity over the last 15 years has been dedicated to study absorbing aerosols, their interactions with solar (SW) and infrared (LW) radiation and their direct radiative effect (DRE). The aim of my research is to quantify the intensity and spectral signature of aerosol absorption and scattering properties, such as the complex refractive index, and to understand their variability as a function of the emission source and atmospheric ageing of the particles. In particular, I aim to estimate how composition, size, shape and mixing state influence the aerosol absorption and scattering, and to produce parameterisations that describe this variability, so to provide usable informations to improve aerosol description in climate models and remote sensing algorithms. The methods I use in my research include experimental measurements in the CESAM large atmospheric simulation chamber (Chambre Expérimentale de Simulation Atmospherique Multiphasique) at LISA, which is my tool of predilection, as well as field observations, laboratory analytical techniques, analysis of ground-based and satellite remote sensing measurements, and regional and global models.

In my research I have set up original experiments in the CESAM chamber to study the spectral optical properties of mineral dust. These experiments have produced new information on the absorption properties and complex refractive index of global dust in the visible and mid-infrared range (0.4-15 µm), which paved the way for significant advances in the evaluation of the DRE and remote sensing of dust. I have subsequently developed a new line of research at CESAM on the study of the optical properties of BC and BrC, mostly looking at primary combustion emissions. I have also conducted studies aimed at investigating the optical and DRE properties of aerosols in mixing zones, where primary and secondary species, anthropogenic and biogenic, cohexist and interact. The results to date have highlighted the power of the laboratory simulation approach, and its synergy with field observations and modelling tools, to elucidate the processes and document the properties that are needed to understand the role of absorbing aerosols on the radiation budget and the climate system. In fact, the realism of aerosol generation and ageing that can be reproduced in a chamber, together with the controlled conditions that the laboratory can provide, are fundamental to producing relevant data for guiding the improvement of climate models and remote sensing algorithms.

My future research activity will be dedicated to further progress in the investigation of the climate-relevant properties of dust, BC, and BrC via the laboratory simulation approach. In particular, I will work to extend the spectral range of documented optical properties from the ultraviolet to the far infrared, including the study of key properties for remote sensing, such as polarisation. I will also work to improve the representation of the aerosol shape in the restitution of optical properties. I will strengthen the activity to study the link between optical properties, composition and mixing state. To do so, I will target both well-established dust sources but also encompass to emerging ones, such as dust from high latitude areas, and I will explore the range of formation pathways of BrC and the impact of ageing on the absorption of BC- and BrC-containing aerosols. Finally, I will extend my activity towards the study of the IN properties of dust, BC and BrC, which is particularly important for understanding the whole radiative effects of aerosols, particularly in polar environments. In order to make progress on all these subjects, the key aspect will be to design laboratory experiments reproducing increasingly realistic and complex conditions (humidity, mixture of species, multiphase chemistry, ageing time) representative of the diversity of situations encountered in the atmosphere.