Temporal and spatial changes of monthly/annual precipitation in the upper reaches of the Hanjiang River were analyzed by using empirical orthogonal function

moving average

and linear regression analysis.Results showed that annual precipitation manifested a decreasing trend during the last 50 years on the whole.Monthly precipitation varied with a major decrease in April and September

but a slight increase in June and August.A major climatic shift occurred in the upper reaches of the Hanjiang River from 1980 to 1988.The shift caused a change in atmospheric circulation pattern with a decreased intensity of southwest monsoon in spring and autumn and an increased intensity of southeast monsoon in summer.Southwest monsoon could induce rainstorms and floods from June to early-middle July and in September.In the periods

reduction in precipitation possibly caused a reduction in the occurrence of flood.Southeast monsoon could cause rainstorms and floods in the late July and August

in which the enhanced monsoon possibly cause an increase in the occurrence of rainstorm and flood.These findings are of great importance in water resources and energy development and flood mitigation in the upper reaches of the Hanjiang River.