青藏高原中东部冬夏高层水汽时空特征分析

利用青藏高原中东部地区16个探空站的1979—2008年各标准等压面上的月平均探空资料对青藏高原中东部地区500～200hPa高层水汽冬夏季时空分布特征及变化趋势进行了研究,结果表明:①空间分布上,青藏高原的水汽空间分布冬夏两季呈现出一致明显的西北—东南走向,高原南部水汽年际变化波动较大,北部较稳定;夏冬两季水汽总体呈现一致变化,同时夏季还存在南北向的反相位区域异常变化,冬季则表现为东西向的反相位变化;②时间变化上,青藏高原夏季水汽总体呈现出较弱的上升趋势,1979—1995年水汽有下降趋势,1996—2005年转为增加趋势,突变主要在1997、2006年;冬季水汽总体为弱下降趋势,1979—1984年水汽为下降趋势,1985—2004年增长并保持稳定,突变主要在1986、2005年;同时青藏高原水汽还存在西部水汽增加而东部水汽呈减少趋势的区域变化特征。

Spatial and Temporal Characteristics of High Level Water Vapor over Mid Eastern Tibetan Plateau

The spatial and temporal characteristics of water vapor from 500 hPa to 200 hPa level in winter and summer are analyzed by using the monthly mean radiosonde data at various levels of 16 stations over the mid-eastern Tibet Plateau from 1979 to 2008.The results indicate：（1） The spatial distribution of winter and summer water vapor over the mid-eastern Tibet Plateau shows obvious northwest-southeast direction.The inter-annual fluctuation of vapor over the southern plateau is bigger in winter and summer,relatively stable in the northern plateau.Water vapor changes identically in general in summer and winter,and there also exists north to south reverse-phase regional anomaly change in summer,while there is east to west reverse-phase change in winter.（2） The water vapor in summer shows a weak rising trend over time generally,negative during 1979-1995 and positive during 1996-2005,with the breakpoints in 1997 and 2006; the water vapor in winter as a whole shows a slightly decreasing trend,negative during 1979-1984,stably during 1985-2004 with the breakpoints in 1985 and 2005.In general,there is a positive trend in vapor over the western plateau and a negative trend over the eastern plateau.