The Variation Characteristics of Extreme Precipitation Indices in Zunyi Area During 1960-2015

According to the temperature data of 13 weather stations at county (district or city) level under Zunyi City from 1960 to 2015, this study has calculated the extreme temperature indexes in Zunyi area. In addition, trend analysis, mutation test and Morlet wavelet function were used to analyze the extreme temperature index sequence and its periodic variation.The results show: (1) 10 indexes including average minimum temperature (TMINmean), minimum value of minimum temperature (TNn), warn night index (TN90P), tropical nights (TR20), maximum value of minimum temperature (TNX), minimum value of maximum temperature (TXn), maximum value of maximum temperature (TXX), average maximum temperature (TMAXmean), warn day index (TX90P), growing season length (GSL) etc in Zunyi area show a positive trend that decreases in turn.Among them, TMINmean, TNn, TN90P, TR20, TNX, TXn, TXX and TMAXmean reach above 0.05 of significance level, and all of them except TMAXmean experienced sudden increase in temperature between 1989 and 2009 that lasts till now, which means that obvious increase in extreme temperature still continues. The trend of TMINmean is greater than that of TMAXmean, signifying that high temperature weather caused by asymmetric change in temperature is intensifying.(2) 7 indexes including cold night index (TN10p), daily temperature range (DTR), frost day (FD0), cold spell duration indicator (CSDI), ice day (ID0), cold day index (TX10P) and warm spell duration indicator (WSDI) in Zunyi area show a negative trend that decreases in turn.Among them, TN10p, DTR, FD0 and CSDI reach above 0.05 of significance level, and all of them except CSDI experienced sudden change that lasts till now, which respectively shows that obvious range of increase in temperature at night, and asymmetric change in minimum temperature and maximum temperature increase, while frost weather decreases obviously.(3) The period of the strongest vibration of extreme temperature indexes in Zunyi area is between 4 and 32 years, and most of the first strong vibration occurred in the early 1960s.