西藏高原沙尘暴气候特征及成因研究

Climatic Properties and Sandstorm Causes in Tibet Plateau

利用1960-2000年西藏22个台站观测资料和NCEP／NCAR再分析资料，分析了西藏沙尘暴日数的时空特征以及沙尘暴异常的气候成因。结果表明：西藏高原年平均沙尘暴日数分布为西多东少，狮泉河、申扎和泽当为年沙尘暴日数超过10d的中心，它们的年变化特征是1～5月多，7～10月少。年沙尘暴日数的年代际变化特征为中间多、两头少，在20世纪90年代达到最少。青藏高原上空的高空西风急流减弱是导致西藏大风、沙尘暴日数减少的主要原因，影响西风急流偏强（弱）的气候系统是东亚大槽偏浅（深）和青藏高原高压偏强（弱）。沙尘暴日数的年代际异常与高空西风急流、大风日数、降水等要素年代际异常以及沙尘暴区地形地貌等因素关系密切。

The data from 22 observatory stations during 1960-2000 and re-analyzed data of NCEP/NCAR were used to study the spatially and temporally distributing properties of sandstorm days in Tibet Plateau and climatic reason of anomalous sandstorm. The result showed that the distributing laws of annual sandstorm days in Tibet was more in west than that in east, the centers of annual sandstorm above 10 days mainly distributed in Shiquan river, Shenzha and Zedang, where sandstorm appeared more frequently during Jan to May, but less during July to Oct. In the last century sandstorm appeared more frequently in mid-century, however less in earlier and later century, and it was the lest in 1990＇. The main cause of gale and sandstorm days decreasing in Tibet Plateau was that the Westerly over the Qinghai-Xizang Plateau weakened. The strengthening （or weakening） of the Westerly depended on the shallowing （or deepening） of trough over East Asia and the strengthening （or weakening ） of high pressure over Qinghaixizang Plateau. The decadal anomaly of sandstorm days closely related mainly with westerly jetstream, gale days, annual precipitation, and local landform, and so on.