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Accurate inversion of land surface evapotranspiration(ET)in arid areas is of great significance for understanding global eco-hydrological process and exploring the spatio-temporal variation and ecological response of water resources.It is also important in the functional evaluation of regional water cycle and water balance,as well as the rational allocation and management of water resources.This study,based on model validation analysis at varied scales in five Central Asian countries and Chinas Xinjiang,developed an appropriate approach for ET inversion in arid lands.The actual ET during growing seasons of the study area was defined,and the changes in water participating in evaporation in regional water cycle were then educed.The results show the simulation error of SEBS(Surface Energy Balance System)model under cloud amount consideration was 1.34％ at 30-m spatial scale,2.75％ at 1-km spatial scale and 6.37％ at 4-km spatial scale.ET inversion for 1980-2007 applying SEBS model in the study area indicates:(1)the evaporation depth(May-September)by land types descends in the order of waters (660.24 mm)＞ cultivated land(464.66 mm)＞ woodland(388.44 mm)＞ urbanized land(168.16 mm)＞ grassland (160.48 mm)＞ unused land(83.08 mm); and(2)ET during the 2005 growing season in Xinjiang and Central Asia was 2,168.68x108 m3(with an evaporation/precipitation ratio of 1.05)and 9,741.03x108 m3(with an evaporation/precipitation ratio of 1.4),respectively.The results unveiled the spatio-temporal variation rules of ET process in arid areas,providing a reference for further research on the water cycle and water balance in similar arid regions.