Variations of Extreme Cold Winter Events in Southern China in the Past 400 Years

The extreme cold winter events were defined as the ones with the occurrence probabilities lower than the tenth percentile of the probability density function,based on the observed temperature of winter and January in southern China since 1951.The impacts (including freezing of rivers/lakes,widespread snow/ice storms,and cold damages to subtropical/tropical crops)of these extreme cold winter events occurred since 1951,which were adopted to reconstruct the chronology of extreme cold winter events derived from Chinese documents in southern China during 1600-1950.The most frequent occurrences of extreme cold winter events were observed during 1650-1699,1800-1849 and 1850-1899,with frequencies twice as many as that in 1950-1999.The frequencies of extreme cold winter events in 1600-1649 and 1900-1949 were a little higher than those in 1950-1999.In contrast, the frequencies of extreme cold winters during 1700-1749 and 1750-1799 were close to those in 1951-1999.Moreover,the occurrence of extreme cold winter events happened year by year or every other year in most of cases.Meanwhile,the intensities of some historical cold events exceeded those of the coldest winter events since 1951.