Interannual Variations of Autumn Precipitation in China and Their Relations to the Distribution of Tropical Pacific Sea Surface Temperature

The interannual variations of the autumn precipitation in China and their possible causes are analyzed, using the China precipitation data of 160 stations from 1951 to 2008, the NCEP/NCAR reanalysis data, and the sea surface temperature data from the Hadley Center. EOF analysis of the autumn precipitation shows that the first EOF mode mainly reflects the precipitation south of the Yangtze River and the second EOF mode depicts the variation of the precipitation north of the Yangtze River. Both of the two principal components (PC) are characterized with distinct interannual variations, and do not exhibit obvious interdecadal characteristics. Analysis of the circulation situation shows that the first PC is mainly related to the strength of the western Pacific subtropical high and the corresponding anomalous cyclone/anti-cyclone over the Philippines. The second PC is closely connected to the northward/southward movement of the western Pacific subtropical high and the anomalous cyclone/anti-cyclone near Japan. Meanwhile, the first and the second PC are also closely related to the anomalous tropical vertical motion near the east Indian Ocean and the western Pacific, respectively. And the anomalous tropical vertical motion may exert an influence on East Asia circulation through the anomalous meridional circulation. Further analysis reveals that besides the tropical circulation, the two PCs are also closely related to the tropical SST anomaly. The first PC is positively correlated to the east tropical Pacific SST anomaly and negatively correlated to the tropical western Pacific, and the second PC is positively related to both the middle and the tropical eastern Pacific. It is therefore indicated that the different distribution of the tropical Pacific SST anomaly may cause the variation of different precipitation mode through different anomalous tropical circulation.