| Based on daily average temperature,precipitation,maximum and minimum temperature data of 6 meteorological stations in Bazhong,Langzhong,Gaoping,Suining,Yibin,and Xuyong in the recent 60 years(1960-2019),the methods of linear trend,M-K mutation test,RClim Dex(1.0)model and Pearson correlation analysis were used to study climate change and extreme climate events in the hilly area of central Sichuan Basin.The main conclusions are as following:(1)The characteristics of climate change in the area in the recent 60 years.(1)In the recent 60 years,the average annual temperature in the area has fluctuated and increased,with the temperature rising faster in the south and slower in the north.The order of the heating rate of the six places is Yibin(0.15? /10a)> Xuyong(0.12)?/10a)> Langzhong(0.09 ? /10a)> Gaoping(0.06 ? /10a)= Suining(0.06 ? /10a)>Bazhong(0.01?/10a).The interdecadal change trend of the average annual temperature in this area is "first decrease and then increase"(declining trend from 1960 s to 1980 s,and rising trend after 1980s).(2)In recent 60 years,the annual precipitation in Yibin,Xuyong and Langzhong showed a decreasing trend(-38.3mm/10 a,-1.96mm/10 a and-3.28mm/10 a,respectively),while the annual precipitation in Bazhong,Gaoping and Suining showed an insignificant and weak increase(0.44mm/10 a,5.04mm/10 a and4.55mm/10 a,respectively).The decadal oscillation of annual precipitation in this area is obvious.(3)In recent 60 years,except for Bazhong and Suining,the abrupt changes of the average annual temperature in the area were not obvious,and the other four sites had obvious abrupt changes and concentrated in 2000?2012(Langzhong in 2012,Gaoping in 2005,Yibin in 2000,and Xuyong in 2005 ?2008).The abrupt change of annual precipitation was obvious only in Yibin(1979-1984).There was no obvious abrupt change in annual precipitation in the other 5 places.Based on the abrupt change test results of annual mean temperature and annual precipitation,the main abrupt change point of annual mean temperature(2005)in this region was determined as the major abrupt change point of climate in this region.(2)The change characteristics of extreme climate events in this area in the recent60 years.(1)In the recent 60 years,the intensity,frequency and duration index of extreme temperature indicating warmness in this area have mainly increased significantly,the intensity(except for the daily maximum temperature),frequency and duration index of reflecting cold extreme temperature are mainly in a significant downward trend.Among them,the number of high temperature days(SU35)has the fastest rising rate,and the number of cold night days(TN10p)has the fastest falling rate.(2)In the recent 60 years,only 20 mm precipitation days(R20)and continuous humid days(CWD)in this area have an insignificant and weak downward trend;other extreme precipitation indexes have an insignificant upward trend,of which heavy precipitation(R95p)and extreme heavy precipitation(R99p)has a rapid rise.In the recent 60 years,Yibin's extreme precipitation index has been mainly in a downward trend,while the other five places have an upward trend in extreme precipitation indexes.(3)In the recent60 years,the main mutation points of the extreme temperature indexes in this area appeared in the 1990 s,2000s and 2010 s.There are many mutation points in each extreme precipitation index,but most of the mutation points are not obvious.(4)The inter-annual variation trends of various extreme temperature indexes before and after the abrupt climate change are quite different in different regions.After the abrupt climate change,the multi-year average values of the extreme temperature index only mainly decreased in the number of cold days(TX10p)and cold night days(TN10p),while the multi-year average values of other indexes increased mainly.Before the climate abrupt change,the inter-annual variation trends of various extreme precipitation indexes in this area were quite different;after the climate abrupt change,the number of20 mm precipitation days(R20)and continuous wet days(CWD)showed an increasing trend,while the other extreme precipitation indexes showed a decreasing trend.All the extreme precipitation indexes(except continuous dry days(CDD))in Yibin decreased after the mutation,while the other five areas mainly increased.(3)The response relationship of extreme climate events in this area to regional temperature changes in the recent 60 years.(1)The intensity,frequency and duration index of warm extreme temperature in the area in the recent 60 years is positively correlated with the average temperature,while the frequency and the duration index of cold extreme temperature is mainly negatively correlated with the average temperature.The extreme temperature frequency index responds strongly to regional temperature changes.In the recent 60 years,the correlation between the extreme precipitation indexes and the regional average temperature is weak.Most of the extreme precipitation intensity and frequency indexes are mainly weakly negatively correlated with the regional average temperature.The number of consecutive dry days in the extreme precipitation duration index is mainly weakly positively correlated with the regional average temperature.The number of consecutive humid days is mainly weakly negatively correlated with the regional average temperature.(2)Before and after the abrupt climate change,the warm extreme temperature intensity,frequency and duration index are positively correlated with average temperature,while the cold extreme temperature frequency and duration index are mainly negatively correlated with average temperature.After the mutation,the correlation between the number of warm night days(TN90p)and the average temperature increased,and the correlation between the number of cold night days(TN10p)and the average temperature weakened.Except for the increased correlation between the extreme precipitation index in Langzhong and the average temperature after the climate abrupt change,the other five places have little correlation before and after the abrupt change. |
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