Abstract:
The amount of precipitation shows clear stages in the summer half year in Guizhou,which incorporates the interdecadal timescale of the rainless-rainy-rainless stages.Without the interdecadal trend,the provincial data of the amount of precipitation in the summer half year from 1978 to 1994 is used for EOF analysis,whose the variance contribution of the first mode is 36%,the spatial distribution is the in-phase and the interannual variance of the regional precipitation is uneven.The abnormal precipitation pattern of the EOF1 is found during April to September,expecially in the July and August.Based on the coefficient of correlation between the PC1 and vapor flux field and the circulation field,we find that the -+- abnormal distribution of the geopotential height along 120E over the East Asia-Pacific,the formation and maintenance of the abnormal anticyclone over the Guizhou and abnormal increase of the upper westerly jet are the main reason for the low rain.With the the typical years,the low rain of Guizhou in summer half year account for 80%,which is following the cold-phase of the surface sea temperature(SST) in the middle and the eastern equatorial Pacific.And the low rain of Guizhou in summer half year account for 100%,which is following the LaNina.Based on above the main findings,the abnormal circulation is caused by the abnormal SST in the middle and the eastern equatorial Pacific having the stability and sustainability,and having the significant lag-effect,expecially in the following year of the LaNina.