[A-AS03] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS03-P09] Definition of a new East Asian subtropical summer monsoon index

*hongming yan¹ (1.Yunnan Meteorological Administration)

Keywords:East Asian summer monsoon, Summer rainfall in China, Three kinds of rainfall pattern, Circulation anomalies over northwestern Pacific

Based on precipitation data of 160 observation stations in China and NCEP / NCAR reanalysis atmospheric circulation data from 1958 to 2014, the relationship between summer precipitation in China and wind at low and high level is firstly investigated. Then a new East Asian subtropical summer monsoon index is defined using 200-hPa zonal wind closely relating to three kinds of summer rainfall in Eastern China. The results show that the new index may well reflect not only the integrated impact of the circulations over high and low latitudes, but also summer precipitation difference characteristic between northern and southern China. Strong East Asian summer monsoon years, strengthen high-level westerly, North position of cold air activity, strengthen the low-level West Pacific subtropical high pressure with position to the north resulting in strong south-west flow over Eastern East Asian, type I rainfall occurring to Eastern China; circulation changes is just the opposite in weak East Asian summer monsoon, type Ⅲ rainfall occurring to Eastern China. Compared with the existing East Asian summer monsoon index, the new index has a great advantage in reflecting the precipitation difference between eastern and southern China.