1971—2005年西藏主要农区农田蒸散量变化特征及其与环境因子的关系  

Changes in Evapotranspiration in the Main Agriculture Areas of Central Tibet and Its Relation to the Environment Factors in 1971—2005

作　　者：杜军[1] 边多[2] 拉巴[1] 周刊社[1] 石磊[1] 

机构地区：[1]西藏自治区气候中心,西藏拉萨850001 [2]西藏高原大气环境科学研究所,西藏拉萨850001

出　　处：《冰川冻土》2009年第5期815-821,共7页Journal of Glaciology and Geocryology

基　　金：国家自然科学基金项目(40865008;40761005)资助

摘　　要：利用1971—2005年西藏"一江两河"主要农区4个气象站点月平均最高气温、最低气温、降水量、风速、相对湿度、日照时数等资料,应用Penman-Monteith模型计算了农田蒸散量,分析其空间分布、年际和年代际变化特征,并讨论了影响蒸散量变化的气象因子.研究表明:近35a西藏主要农区年蒸散量表现为不同程度的减小趋势,为-16.5～-71.6mm.(10a)-1,以泽当减幅最大;四季蒸散量均呈现为减小趋势,以冬季减幅最明显.土壤水分年亏缺量呈明显的减少趋势,平均每10a减小59.6mm,特别是近25a(1981—2005年)减幅更明显.20世纪70年代至90年代年、季蒸散量均为逐年代减小趋势.90年代与80年代比较,主要农区各季土壤水分亏缺量都有不同程度的减小,尤其是夏季由亏缺转为盈余.日照时数和平均风速的显著下降,以及平均相对湿度的明显增加可能是蒸散量显著下降的主要原因,平均气温日较差的显著减小和降水量的增加在蒸散量减少趋势中也起着重要作用.Based on four observational station＇s data of monthly maximum temperature, minimum temperature, precipitation, wind speed, relative humidity and sunshine duration in the central Tibet from 1971 to 2005, the evapotranspiration （ETo） is computed from Penman-Monteith Model. The inter-annual change, inter-decadal variation and the seasonal ET0 and water balance are analyzed; also the impactive climatic factors for the change trend of ET0 are discussed through studying the relationship between ETo and climatic elements such as sunshine duration, mean wind speed and diurnal temperature range. The main results are as follows： 1） In terms of inter-annual variation, there is a decreasing trend of annual ETo in central Tibet in the last 35 years, with a decreasing rate of 16.5-71.6 mm· （10a）^-1, especially in Zetang. A significantly decreasing trend of seasonal ETo takes place, especially in winter. Annual water deficien cy of soil moisture is decreasing, with a decreasing rate of is about 59.6 mm· （10a）^-1, especially in the last 25 years （1981-2005）; 2） In terms of inter-decadal variations, the annual and seasonal ETo decreased apparently from 1971 to 2000. Compared with that in the 1980s, the seasonal water deficiency of soil moisture decreased to different degree in the 1990s, specifically in summer, when the deficit became surplus; 3） It is thus obvious that the decrease of the ETo is mainly caused by the significant decrease of the sunshine duration and wind speed, as well as the obviously increase of mean relative humidity. In addition, the decreasing daily temperature range and increasing precipitation may also play an important role to the decrease of the ET0.

关 键 词：蒸散量 水分盈亏量 年际和年代际变化 西藏“一江两河”流域 

分 类 号：P467[天文地球—大气科学及气象学]