摘要:利用ERA-Interim和APHRO_MA资料分析了1979～2007年间青藏高原西部春季（3～5月）降水的年代际变化趋势及可能原因。结果表明，青藏高原西部局部区域春季降水呈显著减少趋势，降水的变化趋势与其西南部辐合上升运动及阿拉伯海北部水汽含量变化存在联系。发现研究区春季降水增加时伴随其西南部显著的辐合上升异常，同时高层（500 hPa）位势高度场负异常中心与环流的气旋式正异常中心一致，而低层（850 hPa）的辐合上升异常相对较弱；研究区春季降水增加同时伴随阿拉伯海北部至研究区西南部的高、低层比湿正异常，其中低层的比湿正异常更为显著，其正异常中心均位于阿拉伯海北部。上述区域的水汽输送能解释研究区春季降水55.3%的变化，同时两者的变化趋势具有很好相关性。研究显示1979～2007年间研究区春季降水呈下降趋势主要是由阿拉伯海北部低层向印度次大陆水汽输送减少，以及研究区南部高层辐合上升运动减弱造成的。青藏高原西部春季降水变化趋势和相关区域水汽变化的一致性，可以为分析高原气候变化提供依据。
关键词:高原西部/
春季降水/
变化趋势/
水汽输送
Abstract:Using ERA-Interim and APHRO_MA data, the spring precipitation decadal trend in the western Tibetan Plateau during 1979-2007 and its possible causes were analyzed. The results indicate that the change in spring precipitation in the western Qinghai-Tibet Plateau presented a significant decreasing trend, which is clearly related to both the convergence rising in the southwestern Tibetan Plateau and water vapor transport from the northern Arabian Sea. A significant convergence anomaly was found to be generated when the negative high-level (500 hPa) geopotential height field and negative low-level convergence (850 hPa) were occupied, which provided the dynamic conditions for spring precipitation in the southwestern Tibetan Plateau. Moreover, the location of the negative high-level geopotential height field anomaly was consistent with the cyclonic anomaly center in the wind field, while that of the low-level convergence was relatively weak. The spring precipitation anomaly was accompanied by both specific humidity anomalies at the high- and low-level geopotential height fields in the northern Arabian Sea; however, the positive specific humidity anomalies of the lower layers were more significant. The water vapor transport in the northern Arabian Sea accounted for 55.3% of the total spring precipitation change in the southwestern Tibetan Plateau. The study shows that the decreasing trend of spring precipitation in the southwestern Tibetan Plateau from 1979 to 2007 was mainly caused by the decreasing water vapor transport from the lower layer of the northern Arabian Sea to the Indian subcontinent and the weakening high-level convergence of the southern Tibetan Plateau. The consistency of trend in spring precipitation in the western Tibetan Plateau and water vapor changes in related areas can provide guidance to analyze the climate change in the Tibetan Plateau.
Key words:the western Tibetan Plateau/
Spring precipitation/
Variation trend/
Water vapor transport
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