Precipitation above the Antarctic ice sheet : a combined approach of observations and modeling

• Main Author: Roussel, Marie-Laure
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL), Institut Polytechnique de Paris, Christophe Genthon, Jean-Louis Dufresne
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2023
• Subjects: Antarctic; Atmosphere; Precipitation; Observation; Remote sensing; Modeling; Antarctique; Atmosphère; Précipitations; Télédétection; Modélisation; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; [SDU.STU.ME]Sciences of the Universe [physics]/Earth Sciences/Meteorology; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; The Antarctic; Austral; South Pole; Dumont d'Urville; Dumont-d'Urville; Antarc*; Antarctique*; Ice Sheet; South pole
• Online Access: https://theses.hal.science/tel-04540632; https://theses.hal.science/tel-04540632/document; https://theses.hal.science/tel-04540632/file/114673_ROUSSEL_2023_archivage.pdf

The Antarctic ice sheet, whose surface mass balance is primarily driven by precipitation, stores over 30 million cubic kilometers of ice (equivalent to about 60 meters of global sea level rise). Any disturbance to this ice sheet has a direct impact on the global sea level. Unfortunately, the processes responsible for precipitation are extremely challenging to observe due to the complex weather conditions in the Antarctic environment, and thus, they are not well understood. By combining data from various instruments - satellite-borne radar, in-situ measurements, surface remote sensing, as well as weather and climate models - the objective is to obtain the best possible synthesis, accurately representing precipitation in its environment (including the vertical dimension) and improving the ability to forecast its evolution. A preliminary global and regional climatological study of cumulative surface precipitation has been conducted. An evaluation of recent modeling advancements (CMIP and ERA5) compared to the single dataset derived from satellite observations (CloudSat) over four consecutive years at the continental scale has highlighted the complexity and significant discrepancies in representing precipitation at the South Pole. There are fewer outliers in the simulated precipitation amounts, but there is no notable improvement in the positive bias of the models (overestimation of mean precipitation rates on both continental and regional scales, throughout the year, regardless of the season). Subsequently, a local event-based analysis of precipitation was pursued as part of the YOPP campaign, allowing for the study of both surface and vertical aspects during a complete austral summer season. The divergence between atmospheric models, reanalyses, and observations concerning precipitation amounts is noteworthy. A positive bias needs to be considered when using modeling data, affecting both the intensity and frequency of precipitation events. The analysis of local observational data from Dumont d'Urville, acquired ...