Climatic characteristics and variability of thunderstorm in higher latitude plateau of China

Based on the observational thunder storm data of 115 stations in Inner Mongolia for1971-2007,by using the statistical software of SAS,the method of Mann-Kendall test and wavelets,the thunderstorm climatic characteristics are analyzed.The results show that the regional differences of thunderstorm days are significant in Inner Mongolia,the annual-average thunderstorm days are the least in west region of Inner Mongolia and the most in the central region.The mean annual numbers of thunderstorm days are 28.6,and has a decreasing trend,the rate of the climatic tendency is-2.09d/10a.Mann-Kendall test shows that there was an abrupt change in the1990s.The thunderstorm has obvious monthly and seasonal change,over 75﹪of thunderstorms in a year occurred in summer,the period from May to September is the season when thunderstorm occurred the most frequently,and the probability is extremely low in winter.The results from wavelets analysis show that the variation period of annual number of thunderstorm days is about the short periods of 2 years、3 years、5 years、8 years and the long periods of 12 years and 20 years.