| Global warming has led to the frequent occurrence of extreme temperature events that have significant impacts on human life,agricultural production,land use and natural ecosystems.The ?PCC's fifth report also pointed out that the temperature has increased0.85? during 1880-2012.Therefore,understanding the temple-spatial evolution of extreme climate event is s critical to the evaluation of the influences of extreme events in nature.The obtained results are useful for guiding disaster-prevention efforts in different regions of China.In this study,we analyzed the extreme temperature,extreme precipitation and extreme drought in different sub-region of China.The future extreme climate indices time series from 2021 to 2100 under the RCP4.5 and 8.5 scenarios were statistically downscaled using the NWA?-WG method.The main results of our study are:(1)FD0 and TN10 p had decreasing trends,and TNn had increases at more sites than decreases;however,TD30,TX90 p and TXx showed consistently increasing trends both during historical(1961-2000)and future time periods(2001-2100)under the RCP4.5 and RCP8.5 scenarios.More sites had significant trends in the 6 ET?s over the 2001-2100 period.The decreases in FD0 and TN10 p reached 31.4 and 27.4 days over the period 2021-2060 and42.6 and 29.7 days over the period 2061-2100,respectively.The increases in TNn,TD30,TX90 p,and TXx reached 8.7 ?,45.3 days,41.6 days and 5.7 ? over the period 2021-2060 and reached 7.2 ?,65.6 days,62.4 days and 6.4 ? over the period2061-2100,respectively.With respect to the averaged values for 552 sites,the primary periods of FD0,TN10 p,TNn,TD30,TX90 p and TXx were 8,8,8,3,3 and 10 years from1961 to 2017 and 4,4,4,2,2 and 3 years under the RCP4.5 scenario from 2021 to 2100,respectively,whereas only the TN10 p and TNn had 2-and 4-year periods under the RCP8.5scenario.Differently from the averaged ET?s over China,increasingly more sites had longer periods from 1961-2017 to 2021-2100 under both the RCP 4.5 or RCP 8.5 scenarios.This outcome meant that many sites had smaller fluctuations and less periodicity from 2021 to2100 than from 1961 to 2017.(2)The growth period shown decrease trend in most region.Compared to historical value,the growth period of spring wheat decreased by 9 days and 20 days under RCP4.5 and8.5;winter wheat decreased by 20 days and 60 days under RCP4.5 and 8.5;spring maize decreased 5 and 14 days under RCP4.5 and RCP8.5;summer maize decreased by 5 and 10 days under RCP4.5 and RCP8.5.The spring maize and spring wheat showed negative correlation with extreme hot event,and no significant correlation with extreme cold event;winter wheat showed positive correlation with extreme cold event and no significant correlation with extreme hot event;summer maize showed positive correlation with TN10 p,negative correlation with extreme hot event and no significant correlation with FD0 and TNn.(3)The spatiotemporal changes in the EPIs during the three representative years were analyzed in detail.The results showed that the 7 wet EPIs(RX1day,RX5 day,SD?,R20,R95 p,R99p and PRCPTOT)increased nonsignificantly from 1961-2017,and CWD and CDD significantly decreased,while R10 had no significant trend.The abrupt change years of the 10 EPIs occurred 32 and 40 times from 1963-1978 and 1990-2016,respectively,regardless of sub-region.The extremely dry(or wet)events mainly occurred in western(or southwestern)China,implying a higher extreme event risk.The extremely wet,normal and extremely dry events from 1961-2017 occurred in 2016,1997 and 2011 with empirical frequencies of 1.7%,50% and 98.3%,respectively,and daily or monthly precipitation events showed large spatial and temporal variability.In addition,1998 was the second-most extremely wet year(empirical frequency was 3.7%).The monthly precipitation values were larger from February-August in 1998,forming a much earlier flood peak than that of 2016.The 10 EPIs had close connections with ND?s during the 12 months of 1998 and 2016.(4)The GEV,Pearson-?,three-and two-parameter log-normal were generally the best CDFs for the 9 EPIs in China.By comparing the results during 2021-2100 with 1961-2017,the return periods positively correlated with the EPIs.This was especially apparent in southeastern China where the annual mean precipitation was above 1300 mm.The increasing trends were significant for EPIs(especially in northwestern China),including the maximum 1 day precipitation,number of heavy precipitation days,number of very heavy precipitation days,extremely wet days and annual total wet day precipitation.The simple daily intensity index increased in northeastern China,decreased in western China,but had no significant change in other regions.The maximum 5 day precipitation and consecutive wet days decreased in most areas except western China.The consecutive dry days decreased in northern China and increased in southeastern China.This study provides region-and site-specific optimal CDFs and return period information and reveals the spatiotemporal changes of 9 EPIs at different return periods of 10-,20-,50-and 100-years under the RCP4.5 and RCP 8.5 scenarios for 2021-2100.(5)The extreme drought events mainly occurred in sub-regions ?,? and ?,whichdistributed in northwestern China.Around 2090 s under the RCP4.5 the extreme drought from sub-region ? to ? increased by 0.4,0.3,0.1,0.2,0.1,0.05 and 0 times compared the historical values;under the RCP8.5 the extreme drought from sub-region ? to ? increased by 0.8,0.7,0.5,0.4,0.2,0.2,and 0.2 times compared the historical values.Generally,the extreme drought increased significantly,especially under RCP8.5.The increased value of extreme drought in drought area were higher than wet area.The difference of ranged in-6.8-11 and-7.8 to 32 in 40 s and 80 s under RCP4.5.The extreme drought events were increased in most region,especially in sub-regions ?,? and ?.The spacial pattern of RCP8.5 was similar with RCP4.5. |
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