Atmospheric boundary layers in Antarctica : observation and numerical simulation
Except during a few summer afternoon hours, the snow-covered surface of Antarctica is constantly cooling because of radiative processes. This results in a stable, persisting stratification of the atmospheric boundary layer that feeds katabatic winds along the slopes descending from the Plateau to th...
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Other Authors: | , , , , , |
Format: | Doctoral or Postdoctoral Thesis |
Language: | French |
Published: |
HAL CCSD
2014
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Subjects: | |
Online Access: | https://theses.hal.science/tel-01228081 https://theses.hal.science/tel-01228081/document https://theses.hal.science/tel-01228081/file/BARRAL_2014_archivage.pdf |
Summary: | Except during a few summer afternoon hours, the snow-covered surface of Antarctica is constantly cooling because of radiative processes. This results in a stable, persisting stratification of the atmospheric boundary layer that feeds katabatic winds along the slopes descending from the Plateau to the Ocean. Temperature inversions and wind speeds both peak during the winter, with inversions regularly reaching 25 degrees (C) over the Plateau and winds exceeding 200,km/h along the coast. In the summer, significant inversions remain at night but solar heating leads to the formation of convective layers near the surface in the afternoon. With berms and large, empty slopes constantly covered with snow, Antarctica is a unique and perfect laboratory for the study of transitions between turbulent regimes and of the turbulence within stable and katabatic boundary layers. The investigation of these processes is usually made difficult by their sensitivity to heterogeneities at the surface. This thesis work documents three typical "text-book" summer cases: the diurnal cycle on the Antarctic Plateau, the generation of a local katabatic wind and the katabatic forcing of the boundary layer. The investigation of these three cases uses in-situ data. For two of these cases, the observational data has fed and been completed with some Meso-NH model simulation outputs. The first case focusses on the diurnal cycle at Dome C. On the Antarctic Plateau, Dome C is a flat, homogeneous area far from oceanic perturbations. Since a few years, a 45 meters tower samples the boundary layer there. In the summer, the diurnal cycle there is characterized by clean signals in both temperature and winds, with a nocturnal low-level jet within the boundary layer. A two-days data set representative of the rest of the summer has been selected for analysis and is used in the GABLS4 comparison study prepared in collaboration with Meteo France. Single-column simulations have been run for this comparison work launched in June. The second case examines a local ... |
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