Relationship between Winter Rainfall in South China and Preceding Heat Content Anomaly over Western Pacific Warm Pool and Its Possible Mechanism

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By using the historical SST data provided by Japan Meteorological Agency,NCEP / NCAR reanalysis data,SST data from Hadley center,and the daily precipitation at wintertime in 1979-2010 from 753 stations in China,the relationship between winter rainfall of South China and the preceding heat content anomalies over western Pacific warm pool is studied. The results showthat winter rainfall in South China is negatively related to the heat content anomalies at 0 ~ 200 m over the key area of 6. 5°N-11. 5°N,160. 5°E-172. 5°E in June and July,thus the heat content over the key area could be regarded as a precursor of the winter rainfall. The difference field of the atmospheric circulation in winter between the cold years and the warm years resembles the regressed atmospheric circulation field against the sign reversal of heat content index defined within warm pool. It is found that there is an anomalous teleconnection on the East Asian coast in the 500 h Pa height field,with anomalous lowin South China accompanied by cyclonic circulation on 850 h Pa and divergence in upper troposphere,and with anomalous anticyclonic circulation near Philippines which significantly enhances water vapor transport to South China. It indicates that the winter rainfall in South China is more( less) in cold( warm) years. In summer,the strong westerly anomalies near the equator in the northern hemisphere results in the development of cold( warm) SST to the west( east) of key area. In late autumn,an anomalous anticyclone centered in Philippines is formed on the west of the cold SST anomalies,which is strengthened during the winter. The anomalous enhanced warm air on its northwest side transport water vapor to South China. At the same time,the anomalous Walker circulation,excited by the warm SSTA in the central and eastern Pacific,has sinking branch in the equatorial western Pacific,strengthening the Philippines anticyclone and rising motion in South China. It is the above processes that lead to more( less) winter rainfall in South China in the years of cold( warm) SST over the key area.