Analysis of precipitation events changes and causes for rainstorm events reduction in North China

Based on the daily precipitation data of 1961 similar to 2008 from 37 meteorological stations and NCEP, ECMWF reanalysis grid data, the precipitation events change and rainstorm events reduction occurred in North China were analyzed. The results show that mid-summer rainstorm event has a great impact on the summer precipitation and annual precipitation in North China during recent 50 years. Mid-summer rainstorm events showed significant linear decreasing trend, which was related with water vapor flux reduction into North China through the south border caused by the weakening of East Asian summer monsoon. In addition, mid-summer rainstorm events reduction is also well correlated with the weakening of India convection and the enhancing of Philippine convection, as well as the weakening of 125 degrees E cross-equatorial flow and the strengthening of 145 degrees E cross-equatorial flow. This provides an understanding of precipitation reduction in North China.