The Characteristics of Longitudinal Movement of the Subtropical High in the Western Pacific in the Pre-rainy Season in South China

Using the NCEP/NCAR reanalysis data, the China rainfall data of the China Meteorological Administration, and the sea surface temperature (SST) data of NOAA from 1951-2000, the features of theanomalous longitudinal position of the subtropical high in the western Pacific (SHWP) in the pre-rainyseason in South China and associated circulation and precipitation are studied. Furthermore, the relationship between SHWP and SST and the eastern Asian winter monsoon is also investigated. Associatedwith the anomalous longitudinal position of SHWP in the pre-rainy season in South China, the flow patterns in both the middle and lower latitudes are different. The circulation anomalies greatly influence theprecipitation in the pre-rainy season in South China. When the SHWP is in a west position (WP), theSouth China quasi-stationary front is stronger with more abundant precipitation there. However, whenthe SHWP is in an east position (EP), a weaker front appears with a shortage of precipitation there. Thereexists a good relationship between the longitudinal position of SHWP and SST in the tropical region. Anegative correlation can be found both in the central and eastern tropical Pacific and the Indian Ocean.This means that the higher (lower) SST there corresponds to a west (east) position of SHWP. This closerelationship can be found even in the preceding autumn and winter. A positive correlation appears in thewestern and northern Pacific and large correlation coefficient values also occur in the preceding autumnand winter. A stronger eastern Asian winter monsoon will give rise to cooler SSTs in the Kuroshio and theSouth China Sea regions and it corresponds to negative SST anomaly (SSTA) in the central and easternPacific and positive SSTA in the western Pacific in winter and the following spring. The whole tropicalSSTA pattern, that is, positive (negative) SSTA in the central and eastern Pacific and negative (positive)SSTA in the western Pacific, is favorable to the WP (EP) of SHWP.