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Influence de la couverture de neige de l'hémisphère nord sur la variabilité interannuelle du climat

Abstract : Snow can cover more than 40% of the Earth's land surface during the Northern Hemisphere winter. Because of its influence on the energy balance at the surface, it represents therefore a potential source of climate variability and predictability at the seasonal and monthly timescales. Beyond its local effects, snow cover is able to generate some teleconnections and thereby modulate some remote climatic phenomena. This thesis revisits several aspects of snow-climate relationships using both observed data sets, simulations from the 4th report of the Intergovernmental Panel on Climate Change (IPCC) and the ARPEGE-Climat atmospheric model to perform sensitivity experiments. The influence of Eurasian/Himalayan snow on the Indian summer monsoon, widely reported in the literature, is questioned by the analysis of observed data extended to the 1967-2006 period. However, a predictor associated with large-scale atmospheric circulation over the North Pacific region is proposed to improve the statistical seasonal forecasts of the monsoon rainfall. The influence of the Siberian snow extent in fall on the variability of the wintertime Northern Hemisphere atmosphere seems more robust in the observations. If the IPCC coupled models are unable to reproduce this teleconnection, the sensitivity experiments performed with ARPEGE-Climat confirm the physical mechanism proposed in the literature, depending on the amplitude of the forcing and on the realism of the simulated extratropical circulation mean state. Finally, the atmospheric predictability related to snow is quantified more systematically with ARPEGE-Climat. If the results show a mixed impact on the large scale circulation, relaxation/initialization of the model towards/with a more realistic snow mass leads to a better predictability of surface temperature over Europe and North America. Consequently, snow represents a significant source of climate predictability at the local scale and have remote influence on the extratropical atmospheric circulation. Snow-climate teleconnections should however be confirmed in the coming years and are currently poorly captured by the state-of-the-art climate models.
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https://tel.archives-ouvertes.fr/tel-00562496
Contributor : Yannick Peings <>
Submitted on : Thursday, February 3, 2011 - 2:39:03 PM
Last modification on : Friday, October 23, 2020 - 4:39:00 PM
Long-term archiving on: : Wednesday, May 4, 2011 - 2:27:48 AM

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Yannick Peings. Influence de la couverture de neige de l'hémisphère nord sur la variabilité interannuelle du climat. Climatologie. Université Paul Sabatier - Toulouse III, 2010. Français. ⟨tel-00562496⟩

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