Correlation between the subtropical high abnormal longitudinal position and the East Asian summer monsoon system

Using the NCEP/NCAR reanalysis data and the OLR(outgoing longwave radiation) data from NOAA during 1980—2010,an index is defined to describe the longitudinal position of the western Pacific subtropical high based on 500 hPa potential height variation in the key areas.With the index,an investigation is carried out closely with the East Asian summer monsoon system,and the circulation and convective activity differences are revealed in the monsoon area as the subtropical high position is abnormal in June and July.Results show that the abnormal eastern-western position of the subtropical high reflects the Asian summer monsoon intensity,that is,when the subtropical high position is west(east),the South China Sea's summer monsoon is weak(strong),and the subtropics summer monsoon is strong(weak).There exists some interaction between the advance and retreat of the subtropical high and members of the East Asia monsoon system.In the western subtropical high years,the South Asia high is strong with eastern position,the monsoon trough is weaker,the long-wave trough develops deeper,the Mascarene high and the Australia high is weaker,and the cross-equatorial flow is also weaker.The situation is contrary in the eastern subtropical high years.