基于GAME-Tibet IOP的青藏高原蒸散研究

Evapotranspiration in the Tibetan Plateau Based on GAME-Tibet IOP Data

由于缺少足够的观测资料,人们对青藏高原上蒸散问题的认识还不充足。以1998年5～9月"全球能量与水循环亚洲季风之青藏高原试验"加强观测试验期(GAME-Tibet IOP)资料为基础,结合1967～2006年40a的气象站数据,计算了6个样点的参照蒸散量和潜在蒸散量,并在此基础上估算了实际蒸散量的大小。结果显示,高原参照蒸散有下降趋势,但在试验期内却比40a平均值明显偏高,且和潜在蒸散之间表现出很强的相关性;试验期内气温、太阳辐射强度、风速以及饱和水气压差等环境因子的值均高于40a的平均状况;太阳辐射强度、风速、饱和水气压差的增强是导致参照蒸散量升高的主要原因,其中以后两者对参照蒸散量的影响尤为显著;试验期内旬实际蒸散量在9～23mm之间波动,6～8月份实际蒸散的总量可达123.3～136.9mm,占同期降水量的38.2%～73.4%;蒸散在高原地气相互作用过程中有重要作用。

The Tibetan Plateau is one of the ideal areas of the world to investigate evapotranspiration because of the minor impact by humans.But the investigation has been insufficient for owing to the lack of sufficient observational data.Based on the data from the Intensive Observation Period （IOP） of the GEWEX Asian Monsoon Experiment （GAME） in the Tibetan Plateau in 1998 and the meteorological observatories during the period 1967 to 2006,this paper presents on analysis of the reference evapotranspiration,potential evapotranspiration and actual evapotranspiration.The result indicated that reference evapotranspiration decreased during the period 1967 to 2006,but obviously higher than the 40-year average from 1967 to 2006.Furthermore,there was a very high correlation （n=72,r2=0.97） exist between reference evapotranspiration and potential evapotranspiration.The air temperature,net total radiation,wind speed and vapor pressure deficit were also higher than the 40-year average during the GAME-Tibet IOP.The analysis showed that the increased of reference evapotranspiration was due to the increased of net total radiation,wind speed and vapor pressure deficit,and regarded the latter two as the major impacts （n=72,P〈0.05）.During the GAME-Tibet IOP,actual evapotranspiration of 10-day average fluctuated between 9 mm and 23 mm.Form June to August,the total actual evapotranspiration could achieve 123.3~136.9 mm,which was 38.2%~73.4% of the precipitation in the same period.These all clearly show that evapotranspiration has played an important role in the Geo-gas interaction of the Tibetan Plateau.