西藏参考作物蒸散量时空变化特征与影响因素

为深入认识西藏参考作物蒸散量(ET_0)的变化特征,采用联合国粮农组织1998年推荐的Penman-Monteith公式计算西藏37个气象站点32 a(1981—2012年)的逐日ET_0,通过联合国防治荒漠化公约提出的全球干旱指数(UNEP)进行气候评价,利用空间插值及Mann-Kendall趋势检验法对西藏及各气候区ET_0时空变化特征进行分析,并通过偏相关分析法对其主要影响因素进行探讨,结果表明:西藏共分为特干旱、干旱、半干旱、干旱半湿润、湿润半湿润和湿润气候区,主要为半干旱气候区。近32 a参考作物蒸散量整体呈减小趋势,变化趋势为-1.508 mm·a~(-1),可将32 a分为3个时段,1981—1989年处于高蒸散阶段,1989年后处于低蒸散阶段,2005年起又持续回升。西藏西部到东部,年际ET_0呈减小趋势。各气候区气象因子的影响基本符合平均气温日照时数平均风速相对湿度,且平均气温、日照时数及平均风速在干旱区的影响较湿润区更为显著。

Spatiotemporal Variation of Evapotranspiration of Referred Crops and the Affecting Factors in Tibet

In order to have a thorough recognition of the variation patterns of reference evapotranspiration (ETo)in Tibet,in this study the Penman-Monteith method,recommended by the United Nations Food and Agriculture Organization in 1998,was used to estimate the daily ETo at 37 meteorological stations in Tibet during the period from 1981 to 2012.Also,the global aridity index (UNEP) proposed by the United Nations Convention on Combating Desertification was applied for the climatic regionalization in Tibet,accompanied by the application of spatial interpolation method and Mann-Kendall Test to explore the spatiotemporal variation of ET0 in different climatic zones in Tibet.The factors affecting the ET0 variation were explored through the partial correlation analysis.Results indicated that Tibet could be divided into the hyper-arid,arid,semiarid,dry sub-humid,moist sub-humid and humid climatic subregions,in which the semiarid subregion was the largest.A general decreasing trend of ET0 with a rate of 1.508 mm · a-1 was detected in whole Tibet in recent 32 years,and this process could be classified into three stages.The evapotranspiration was high during the period from 1981 to 1989,it was low after 1989,but it began to increase after 2005.The annual ET0 was decreased from the west to the east of the study area.The climatic factors contributing to the ET0 variation in Tibet were generally in an order of mean temperature ＞ sunshine duration ＞ mean wind speed ＞relative humidity,and the impacts of mean temperature,sunshine duration and mean wind speed in arid region were relatively higher than those in other climatic areas.