On the role of western Pacific Subtropical High and easterly flows from its south side in May-June precipitation over Fujian province

摘要

Correlation analysis and accumulated anomaly as statistical approaches are employed to investigate the relationship between the western Pacific subtropical high (sub-high for short) and May-June precipitation (MJP) in Fujian and, moreover, NCEP/NCAR reanalysis-calculated vertical integration of transported vapor are used to make a comparative study on differences in circulation and element fields between dry and wet years for May-June in the project province. Results show that 1) the situation of the sub-high weaker than mean and southward of normal favors excessive MJP in Fujian. In dry years the western Pacific positive SSTA area that intensifies the sub-high is to the south of Japan, leading to the sub-high stronger in comparison to normal and northward of mean while in wet years the sub-high takes a more southern position due to the western Pacific 10-25°N SST higher with respect to normal; 2) in dry (wet) years SW warm, moist air is considerably weakened (reinforced) for South China including Fujian. However, the upper-level strengthened SW air-transported vapor arrives at Fujian predominantly via the turning of easterly flows from the south side of the sub-high, a new discovery worthy of further research for understanding the role of warm, wet air originating from the Bay of Bengal in MJP forecasts over the study region.