The Interdecadal Variability Of Summer Precipitation Efficiency In East Asian

In this paper,the spatial-temporal distribution and the interdecadal variations of summer precipitation efficiency in East Asia have been studied by means of EOF decomposition,correlation and regression analysis based on ERA-Interim,GPCC monthly precipitation and NOAA SST reanalysis datasets.The following conclusions have been reached:(1)The summer precipitation efficiency in East Asia possesses two major EOF modes,both of which exhibit obvious interdecadal variations.The EOF1 presents interdecadal variations of mean precipitation that are partitioned into two periods with tipping point in 1998/1999.The EOF2 shows the interdecadal variations of precipitation variability that are also partitioned into two periods with tipping point in 1999/2000.(2)Interdecadal variations of mean precipitation after 1999 can be attributed to the Pacific decadal oscillation(PDO)phase change.The PDO index value remains positive during 1983-1998 period and negative during 1999-2011 period.Warm SST anomalies over the West Pacific excite an anticyclonic circulation over the northern East Asia and a cyclonic circulation south of 35°N,which significantly reduces(increases)the precipitation efficiency north(south)of 35°N in East Asia.The spatial distribution of precipitation efficiency is shifted from the "-?" meridional pattern from south to north to the opposite"+-"pattern.(3)Interdecadal variations of precipitation variability represented by EOF2 can be attributed to the occurrence frequency of EP-type ENSO events.The EP-type El Nino anomalies force out an EAP teleconnection wave train over the East Asia-Northwest Pacific region,which further induces cyclonic circulations over the East Ghina Sea and South China Sea and anticyclonic circulations over the Korea Peninsular.This anomalous circulation pattern results in less moisture transport over East China Sea and South China Sea and more water vapor supply over the Korea Peninsular.Precipitation efficiency exhibits"-+-+"anomalous pattern from south to north in East Asia.There are more EP-type ENSO events during 1979-1999 than the former period of the interdecadal precipitation variability,with the average of once every three years.Variabilities of the precipitation efficiency become more robust during 1979-1999 with prominent"+-+-" or"-+-+"spatial pattern in East Asia.The occurrence frequency drops to once every 5.7 years on average during 2000-2016,making he spatial patterns of alternating positive-negative anomalies become insignificant.