欧亚大气环流对中国北方春季沙尘天气的影响

Impact of Eurasian Atmospheric Circulation on Dust Events in Spring over Northern China

根据1960-2010年全国701个地面站沙尘观测资料分析了中国春季沙尘天气的空间分布和年际变化,发现南疆和内蒙古两个沙尘源区的沙尘指数51年来都呈现出减小的趋势,其中内蒙古沙尘指数总体较小、年际变化较大,而南疆沙尘指数的波动较小。通过分析南疆和内蒙古沙尘指数典型高、低值年春季环流场发现,控制两个沙尘源区的环流场存在明显差异:南疆沙尘指数低值年时,西路入侵的冷空气减少,受此影响蒙古气旋和南疆热低压减弱,导致南疆地区近地面西风减弱,最终导致南疆沙尘天气减少;内蒙古沙尘指数低值年时,西北路和北路冷空气入侵次数减少,地面场上西伯利亚冷高压和蒙古高压减弱,并且蒙古气旋的发生发展受到限制,导致内蒙古西部近地面西北风和偏西风减小,最终导致内蒙古地区沙尘天气减少。

Based on meteorological observation data from 701 meteorological stations in China during 1960- 2010, two dust indices, which are Taklimakan Dust Index （TDI） and Gobi Dust Index （GDI）, were used to characterize the statistical feature of the dust event occurrence. In general, TDI and GDI both exhibit a sud- den decrease in the mid 1980s. Although the intensity of GDI were smaller than the TDI＇s since 1960＇s, its inter-annual variability was larger. We also analyzed the differences of atmospheric circulation between years with high and low dust index values. The results indicated that the low dust index values in Southern Xinjiang was likely caused by the waken Mongolia Cyclone and the thermal low pressure in the Taklimakan region, but that the intensity of Siberia Cold High Pressure and the Mongolia High Pressure became waken was the main mechanism of low dust index values in the Inner Mongolia.