近34a青藏高原年降水变化及其分区

Change of Annual Precipitation over Qinghai-Xizang Plateau and Sub-regions in Recent 34 Years

对高原地区34 a(1971—2004年)82站共13 883 d的逐日降水量资料进行了统计,用REOF方法进行了分区,并讨论了趋势变化。青藏高原地区属季风降水区,在东亚季风、印度季风、高原季风和西风带系统的影响下,降水的局部特征显著。近34 a来高原上的降水量整体呈增加趋势,从20世纪70年代到90年代初期降水变化不大,90年代中后期开始明显增加,尤其是近3 a增加明显。青藏高原干旱地区降水完全取决于夏季降水量,并且降水的相对变率大。从青藏高原地区年降水的分区情况来看,西藏及四川的西南部降水增加最明显,每10 a增加幅度为54.5 mm,其次是青海的柴达木盆地和青海湖地区及甘肃的河西走廊地区。而青海的东部及三江源地区,祁连山区,四川的西北部地区呈减少趋势。高原上高海拔地区的降水在减少,而低海拔地区在增加。

The authors have statistically analyzed the daily precipitation data from 1971 to 2004 of 82 meteorological stations on Qinghai-Xizang Plateau, based on which the climatic subregions have been got by using the REOF method. The change trend of precipitation for each subregion has been studied. Seen from the whole region, the Qinghai-Xizang Plateau situates in the Monsoon rainfall region, and has obvious local characters in the effect of East-Asia Monsoon, India Monsoon, Plateau Monsoon and Westerly system. On the whole, the precipitation on the plateau has an increasing trend in the past 34 years, with slight variation from 1970s to early 1990s and obviously increasing since then, especially in the recent 3 years. Summer rainfall completely determines the precipitation of arid regions in the plateau, so the precipitation has larger relative variability. Seen from sub-regions, the precipitation increased most remarkably in the south parts of Tibet and Sichuan, with a rate of 54. 5 mm per ten years, the following are Qaidam Basin, Qinghai Lake, and Hexi Corridor. Whereas, the precipitation decreased in the east of Qinghai, the source region of the three large rivers, the Qilian Mountains, and the northwest of Sichuan. Geographically, precipitation decreased in the high altitude region and increased in the low altitude region.