西北地区空中水汽输送时变特征及其与降水的关系

Spatial and temporal distribution of water vapor and its relationship with precipitation over Northwest China

利用西北地区25个气象观测站1964-1998年的降水量等多个气象要素资料以及1980—1998年西北地区高空风场资料,分析了西北地区空中水汽分布及其输送的年代际变化特征,并探讨了与降水量变化的关系．结果表明:西北地区上空对流层内的水汽含量具有区域差异,在西北地区东部和西部水汽较丰富,而西北地区中部水汽含量极少,这与西北地区降水的地理分布基本一致;西北地区对流层整层的水汽含量从20世纪60—80年代初有下降趋势,而在20世纪80年代中期以后又开始出现显著增加的趋势．在年际变化上,降水的变化趋势与水汽的变化趋势在部分年份里存在一定差异,这主要因为降水是由多种因素决定的;西北地区水汽输送主要以纬向为主,且水汽输送两个大的通道对应降水的极大值中心;全球变暖对西北地区空中水汽分布有一定影响．

Based on the climatic data of precipitation and other observations at 25 meteorological stations covering 1964-2001 as well as wind field data in whole air column covering 1980-1998 in Northwest China （the area is within the north of 35°N and west of 105°E of China）, the climatic characteristics of water vapor, its flux and the relationship between water vapor and precipitation were studied. The results show that： the average climatic water vapor in the whole air column over Northwest China is concentrated in thc east and west areas, and the least in the middle part and it is almost the same as the distribution of precipitation. On the average, the water vapor over Northwest China decreased obviously during the 1960s and themiddle 1980s but has been increasing since the late 1980s and the variation trend of precipitation is slight different from that of water vapor. This is because the factors acting on precipitation are not just water vapor. The water vapor flux over Northwest China is mainly along the latitude dircction and the largest rainfall center is consistent with the place where water vapor transport is thc strongest. Global warming also has important influence on the water vapor over Northwest China.