中国西北及青藏高原沙尘天气演变特征

Evolvement characteristics of dust weather events in Northwest China and the Tibetan Plateau

利用西北地区及青藏高原177个气象站1971～2006年的观测资料,分析了该区域发生的不同等级的沙尘(浮尘、扬沙、沙尘暴)的空间分布特征、移动规律和变化趋势.结果表明,12月～翌年2月,沙尘暴和扬沙发生的中心位于高原西南部;3月,除高原西南部外,在河西走廊及其东部也出现沙尘暴和扬沙;4～5月,高原西南部沙尘暴和扬沙的日数迅速减少,发生区北移到35oN～40oN的区域.南疆和河西走廊及其东部,是春季浮尘的高发区.从12月到4月,沙尘暴和扬沙的高发区是逐渐向北和向东移动的;而浮尘的高发区主要在南疆,不随月份的变化而移动.近36a来,沙尘的影响范围和发生日数,均呈显著减小的趋势.易于发生沙尘天气的区域,同时也是沙尘发生日数减小趋势最为显著的区域.

The dust weather events with different grades （floating dust, blowing sand, and dust storm） were analyzed based on the observation data from 177 meteorological stations in Northwest China and the Tibetan Plateau during 1971-2006. The spatial distribution, moving law and the variation trend of dust weather frequency were revealed for the past 36 years.The occurring center of dust storm and blowing sand located mainly in southwest of the Tibetan Plateau from December to February; in Hexi Corridor and the areas to the east as well as southwest of the Tibetan Plateau in March. From April to May, frequency of dust storm and blowing sand events decreased rapidly in southwest of the Tibetan Plateau, and the main occurring centre moved northward to the region of 35~N-40~N. The higher frequency of floating dust in spring occured mainly in south Xinjiang, Hexi Corridor and the areas to its east. The centers of dust storm and blowing sand moved gradually northward and eastward from December to April. However, in south Xinjiang region, the occurrences of floating dust did not vary by month. Both frequency and spatial extent of dust weather events demonstrated a remarkably decreasing trend over the past 36 years. The area, which was more prone to dust occurrences, also showed a most remarkable decreasing tendency in dust occurrences at the same time.