Abstract: The inter-annual and inter-decadal variation and abrupt change of 20cm pan evaporation in Aletai,Xinjiang was studied based on 20cm pan evaporation data of 7 weather stations from 1964 to 2001 by using the method of linear trend and Mann-Kendall.The results showed that the highest annual average pan evaporation was occurred in 1970s,and then declined.The highest evaporation was in summer,followed by spring and autumn.Annual evaporation was fluctuation,which was same to spring,summer and autumn.But it increased significantly in winter.There was an obvious abrupt change for pan evaporation in summer and autumn during 1980s.The results indicated that climate change had different performance in different seasons and regions.

Key words: Pan evaporation, Pan evaporation, Climate change, Abrupt change