Seasonal Characteristics of Precipitation Occurrences in the Core Area of the Subtropical High

Based on the National Centers for Envioromental Prediction (NCEP) Reanalysis 2 daily data and the Global Precipitation Climatology Project (GPCP) 1 Degree Daily (1DD) precipitation data from 1997 to 2006, seasonal characteristics of precipitation occurring in the core area of the subtropical high (STH) were investigated by the frequency analysis method. The results indicate that precipitation occurs in the core area of the STH in each season, which is inconsistent with the common knowledge. In summer, there exists 40%-80% of the precipitation frequency in the STH, against less than 50% in other seasons. Generally, the seasonal mean rain rate inside the STH is about 1-2 mm day-1 in winter and less than 4 mm day-1 in summer, which contributes to about 30%-90% of the local total precipitation. In summer, such a contribution is about 50%-90%, and it is less than 40% in other seasons. Statistically, the occurrence frequency of the updraft within the core area of the STH varies from 25% to 75% in summer and less than 25% in other seasons. The results also reveal that there is about 30% of the STH frequency over the eastern China in summer,and the corresponding precipitation and updraft frequencies are 25% and 15% respectively. This is the so-called unique precipitation pattern in summer in eastern China, i.e., precipitation is controlled by the core of the STH. Additionally, more than half of the precipitation occurring in the STH is accompanied with updraft at 500 hPa while less than half is with downdraft at 500 hPa. The former may represent deep precipitation whereas the latter may hint shallow precipitation in the core area of the STH.