Changing Characteristic of Land Surface Evapotranspiration and Soil Moisture in China during the Past 30 Years

The land surface evapotranspiration(ET) and soil moisture used in this paper were retrieved from land surface model(LSM) of NOAH.The variation of land surface ET and soil moisture was analyzed by statistics in six large regions and by four ecosystem types in China.Then the relationship between ET and soil moisture was discussed.The long term trend of land surface ET was increasing in China.The maximum ET occurred in July,while the minimum one was usually at the beginning/end of a year.The trend of ET in South-Central China,Southwest China,East China,Northeast China and Northwestern China was also increasing,agreed with the whole China.The long term variation trend of ET was decreasing in North China,where the maximum ET was 43.091 Billion Cubic Meters(BCM) in 1990.The relative ratio of evapotranspiration of forest was the highest among all the ecosystem types in Northeast,East,Southwest and South-Central China,while the highest one was grassland in North and Northwest China.To compare the amount of water used by evapotranspiration,the biggest forest ET was in Southwest and South Central China,the smallest was in Northwest China;the biggest grassland ET was in Southwest China,the smallest was in Northeast China;the biggest farmland ET was in East China,the smallest was in Northwest China;the biggest ET for desert and wet land was in Northwest and Northeast China respectively.The soil moisture was decreasing in most China regions except for that in Northwest China ever since 1980s,agreed with the whole China.The main impact factors of ET were vegetation fraction and soil moisture.There existed a good relationship between soil water content and evapotranspiration in rare vegetation covered regions.