Spatial-Temporal Characteristics of Summer Precipitation in the East of Southwest China

Based on the daily precipitation data at 20 stations in the east of Southwest China from 1959 to 2006 and daily rainfall data at 740 stations of China,the spatial-temporal evolution features of summer precipitation in the east of Southwest China were studied,using the EOF,Mann-Kendal,MESA,Morlet wave and linear relevance methods.The results show that the precipitation can be divided into three kinds of distributed types,roughly,namely entire regional distribution type,north and south opposite distribution types and west and east opposite distribution types,in which the entire region type is the dominant one and reaches a frequency of more than 60 percent.The summer precipitation presents upward tendency during the discussion phase.The results also show that it is the drought period from 1960s to 1970s,the flood period in the beginning of 1980s and the dryness and the wetness perturbation reinforced and presentation alternately between the middle and the end of 1980s,in which generally the flood is dominant.It is the drought period since the beginning of the 21th centuries.The most obvious years of more precipitation present especially in 1998,1980,1993 since 1959,while the opposite facts present in 1972 and 2006.The interannual and the decadal periodic variation of the summer precipitation are remarkable.There are periodic change of 2～3 and 15 years primarily.The positive correlaltion is obviously between the precipitation in eastern region of Southeast China and regions from Yibin city to Changjiang River Basin,the southeastern of Sichuan and Yunnan Plateau,while the negative correlation is between the studying area and the Sichuan Basin and the edge of Sichuan Province,the centre of North China,the South China and the Southeast Coast of China.