A Modeling Study of the Effects of Anomalous Snow Cover over the Tibetan Plateau upon the South Asian Summer Monsoon

The effect of anomalous snow cover over the Tibetan Plateau upon the South Asian summer monsoon is investigated by numerical simulations using the NCAR regional climate model (RegCM2) into which gravity wave drag has been introduced. The simulations adopt relatively realistic snow mass forcings based on Scanning Multi-channel Microwave Radiometer (SMMR) pentad snow depth data. The physical mechanism and spatial structure of the sensitivity of the South Asian early summer monsoon to snow cover anomaly over the Tibetan Plateau are revealed. The main results are summarized as follows. The heavier than normal snow cover over the Plateau can obviously reduce the shortwave radiation absorbed by surface through the albedo effect, which is compensated by weaker upward sensible heat flux associated with colder surface temperature, whereas the effects of snow melting and evaporation are relatively smaller.The anomalies of surface heat fluxes can last until June and become unobvions in July. The decrease of the Plateau surface temperature caused by heavier snow cover reaches its maximum value from late April to early May. The atmospheric cooling in the mid-upper troposphere over the Plateau and its surrounding areas is most obvious in May and can keep a fairly strong intensity in June. In contrast, there is warming to the south of the Plateau in the mid-lower troposphere from April to June with a maximum value in May.The heavier snow cover over the Plateau can reduce the intensity of the South Asian summer monsoon and rainfall to some extent, but this influence is only obvious in early summer and almost disappears in later stages.

作 者： 劉華強 孫照渤 王舉 閔錦忠   作者單位： 劉華強,閔錦忠(Key Laboratory for Meteorological Disasters and Environmental Change,Nanjing Institute of Meteorology, Nanjing,210044)

孫照渤,王舉(Department of Atmospheric Sciences, Nanjing Institute of Meteorology, Nanjing,210044) 

刊 名： 大氣科學(xué)進展（英文版）  ISTIC SCI 英文刊名： ADVANCES IN ATMOSPHERIC SCIENCES  年，卷(期)： 2004 21(6)  分類號：   關(guān)鍵詞： snow cover   Tibetan Plateau   South Asian monsoon   numerical simulation  

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