青藏高原地区云水时空变化特征及其与降水的联系

利用1984-2009年ISCCP的云量、云光学厚度(COT)、云水路径(CWP)资料,分析了青藏高原云水的分布特征、变化趋势,及其与夏秋季降水、冬春季降雪的联系.结果表明:青藏高原地区大气中的云水有着显著的季节变化与水平分布差异;青藏高原春夏季总云量、高云云量高于秋冬季,CWP、COT与总云量的分布特征具有较好的一致性.高原云量高值区位于喀喇昆仑山与高原东南部;可可西里地区由于羌塘高压的下沉作用为云量低值区.青藏高原总云量在1984-2009年间呈现减少趋势;而CWP在高原总体以增加为主,但在各区域上的变化不一致,高原东部CWP增加而西部出现较弱的减小,这与来自孟加拉湾的水汽输送增加有关.青藏高原中东部地区夏秋季降水受云量减少影响较小而与CWP的增加相一致呈增长趋势;该地区冬春季降雪略有减少,与总云量的年际变化具有正相关.

Temporal and spatial variation features of cloud water and its relation to precipitation over the Tibetan Plateau

The distribution features and variation tendency of cloud water and the relation to summer and fall rainfall and winter and spring snowfall are analyzed over the Tibetan Plateau (TP) by using cloud amount,cloud optical thickness (COT) and cloud water path (CWP) of ISCCP from 1984 through 2009.The influence of cloud amount change on precipitation under climate change background in TP are discussed also.The results show that the distributions of CWP,COT are similar to total cloud amount over TP.There were significant differences in seasonal change and distribution.Total and high-level cloud amounts in spring and summer were more than those in fall and winter.The high values of total cloud amount were located in the Karakoram and southeastern TP,as well as in the low lands in Hoh Xil.Decreasing tendency of total cloud amount is revealed over most of TP by linear regression analysis.However,there were an increasing tendency in CWP in eastern TP and a slight decreasing tendency in western TP.The change in CWP was primarily dependent on the enhanced moisture from the Bay of Bengal.CWP and COT has increasing over the central and eastern TP in recent decades.Precipitation in summer and fall was increasing over most TP,which has tight relation with cloud amount,CWP and COT.There was a little decreasing tendency of maximal snow depth in winter and spring,with a significant correlation to the variation of total cloud amount.The cloud water resources over the central and eastern TP have increasing tendency under global climate change.