1980—2009年藏西北地区水分盈亏量的变化特征

Distribution of Water Budget in the Northwest Part of Tibet During 1980-2009

为了解藏西北地区气候干湿状况,采用研究区近30年来的气象观测资料和彭曼公式,分析了藏西北气候水分盈亏量的时空分布特征和变化趋势。结果表明:藏西北地区水分盈亏量总体表现为水分亏缺的分布特征,无论年水分亏缺量,还是季节水分亏缺量,其分布均由西向东逐渐减少;近30年来藏西北地区年和不同季节水分亏缺量基本呈减少趋势,表明水分亏缺有缓和的趋势;夏季水分亏缺量减幅最大,春季次之,秋季减幅最小;年、夏季和冬季水分盈亏量存在显著突变规律;水分盈亏量与平均气温、平均风速、日照时数基本呈负相关,与相对湿度、降水量呈正相关;降水量增加,日照时数、风速减少可能导致水分亏缺量减少的主要气象因子。

In order to well-understand dry and wet climatic conditions in the northwest part of Tibet, this studyinvestigates the temporal and the spatial distribution and its variation tendency of climatic water budget in theabove region based on the meteorological observation in 1980 to 2009 along with Penman-Monteith equation.Results show that the variation of water budget in the study region generally exhibits a deficit tendency in itsspatial distribution. Both the annual and the seasonal water deficit have the distribution pattern of graduallydecrease from the west to the east part. The annual and seasonal water deficit express a decreasing tendency inthe north part of Tibet which shows that water deficit has assuasive trend during 1980 to 2009. The mostnoticeably water deficit decrease appears in summer, then followed by that in spring and the amplitudereduction of water deficit in autumn is the smallest. The annual water budget and that in summer and winterhave significant mutation rules. The water budget is negatively related to the air temperature, while wind speedand sunshine duration are positively related to the relative humidity and precipitation. As a whole, increasingprecipitation, decreasing sunshine duration and wind speed might be the major meteorological reasons for thedecrease of water budget.