Analysis of Characteristics of Convective Precipitation under Global Warming and Its Impact Factors

The authors analyzed the tendency of the annual and summer average surface temperatures in the Northern Hemisphere for a period covering nearly 60 years and the variation of the convective precipitation occurred in summer (June-August). The possible causes of the variation were also researched in this article by investigating the impact factors of the convective precipitation. The analysis was based on the monthly data, daily and monthly relative humidity, temperature data of NCEP/NCAR, and the daily precipitation records of 60 selected stations in the mid-lower reaches of the Yangtze River using trend analysis and mutation testing method. The results show that for nearly 60 years the annual and summer average surface temperatures in the Northern Hemisphere have been rising with an abrupt temperatures leap in nearly 1998 so that this year can be regarded as an temperature discontinuity. With the increasing effect of global warming, both the frequency and intensity of the convective precipitation events that occurred in summer were enhanced in the reaches of the Yangtze River. In years when the temperature was higher than average, the water vapor content in the upper and middle troposphere showed a continuously decreasing trend and in the lower troposphere showed an increasing trend in July and August. Apart from a few individual years, the heat content at the 700 hPa, 850 hPa, and 1000 hPa levels had an obvious positive trend. The atmospheric instability also showed a clear tendency of strengthening. These factors have a strong correlation with the increasing frequency and intensity of the convective precipitation. It was concluded that changes in water vapor content and enhancement of heat content and atmospheric instability caused by global warming may have an important influence on the increase of convective precipitation events.