Relationship between the Monthly Variation of the East Asia Westerly Jet and the Huaihe River Valley Rainfall Anomaly in Summer

Relationship between the East Asia Westerly Jet (EAWJ) and the Huaihe River Valley (HRV) summer rainfall was investigated month by month, using the NCEP/NCAR reanalysis data and the monthly rainfall data at 160 stations in China from 1979 to 2008. It was found that the HRV summer rainfall is closely related to the monthly variation of the EAWJ. In the years with more rainfall over the HRV, the EAWJ is located northward than normal and the circulation pattern exhibits two ridges and one trough in midhigh latitudes of Asia in June. The cold air activities are weak and the HRV is controlled by anomalous southerlies, which favors more precipitation there. The situation is almost opposite in the years with less rainfall. In the years with more rainfall over the HRV, the EAWJ moves southward to its climatic location, the South Asia high is located eastward than normal, and the western Pacific subtropical high is stronger and is located westward than normal, resulting in more precipitation in the HRV during July and August, and vice versa. The analyses indicate that in June, the change in the intensity and location of the EAWJ is more influenced by the midhigh latitude circulations of Asia. However, in July and August, the intensity and location of the EAWJ is more affected by the variation of the tropical and subtropical circulations.