Analysis on climate characteristics of thunderstorm in China and effect of East Asian summer monsoon on it during 1961-2013

Using the thunderstorm day data from 722 meteorological stations in China from 1961 to 2013, we have conducted a statistical analysis on the characteristics of spatial and temporal distributions of thunderstorm days and its variation in recent 50 years, and discussed the effect of East Asian summer mionsoon on the variation of annual awerage thunderstorm days in China. The results show that the thunderstorm region in China can be divided into four, i.e. northern China' s mid-thunderstorm, southern China' s multi-thunderstorm, Tibetan plateau multi-thunderstorm and northwestern China' s less-thunderstorm (hereinafter referred to as northern region, southern region, plateau region and northwestern region, respectively). The thunderstorm days are the most in summer but the least in winter, while they are intermediate in spring and autumn, with more in spring than in autumn. In spring and winter most of thunderstorm days occur in the southern region, while in summer and autumn most of them are in the plateau region. The annual average thunderstorm days show a decreasing trend with some fluctuation in China in recent 50 years. The trend can be seen at the more than 97.9% of stations, and it is clearer in the southern region than in the northern region. Annual average thunderstorm days in the nationwide and four regions in China has a long oscillation period of 10-13 years and 18 years or so, but a short oscillation period of 4-8 years at different decades, which tends to be more since 2013. There is a clear positive correlation between summer monsoon intensity index and thunderstorm days in China from April to September, and the correlation coefficient is 0.6589 which passes the test at the 0.001 significance level. The average thunderstorm day from April to September in the strong summer monsoon years is over 25% more than that in the weak ones. There is a significant positive correlation between the weakening of East Asian summer monsoon and the reduction of annual average thunderstorm days.