1980—2009年藏西北地区水分盈亏量的变化特征

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。

Distribution of Water Budgetin the Northwest part of Tibet during 1980-2009

In order to well-understand dry and wet climatic conditions in the northwest part of Tibet, this study investigates the distribution and its variation tendency of climatic water budget in above region based on the meteorological observation in the past 30 years along with Penman-Monteith equation. Results show that the variation of water budget in the study region generally exhibits deficit tendency in its spatial distribution. Whatever the annual or the seasonal water deficit, all of them gradually decrease from the west to the east part. The annual and seasonal water deficit expresses decreasing tendency in the north part of Tibet which shows that water deficit has assuasive trend during 1980-2009. The most noticeably water deficit decrease appears in summer, then followed by that in spring and the amplitude reduction of water deficit in autumn is the smallest. The annual water budget and that in summer and winter persists significant sudden change. The water budget is negatively related to the air temperature, wind speed and sunshine duration while positively related to the relative humidity and precipitation. As a whole, increasing precipitation, decreasing sunshine duration and wind speed might be the major meteorological reasons to the decrease of water budget.