The Characteristic Analysis Of Climate Change In The Hinterland Of Three Gorges Reservoir From 1955 To 2015

Based on the data from 1955-2015 of Wanzhou,a county in the Hinterland of Three Gorges Reservoir,linear analysis,Mann-Kendall test and EEMD are applied to analyze the characteristics of climate change.And the correlations among various meteorological factors are studied.The impacts on climate from Three Gorges Reservoir are also researched by the comparison of climate characteristics before and after water storage.Results show that:(1)The climate change of Wanzhou district has obvious inter-annual and inter-decadal fluctuations.The same as our country and southwest areas,annual mean temperature shows a rising trend.The mean temperatures of four seasons are all increasing.And the increasing speed of summer is slowest.Annual mean temperature as well as the temperature of spring,summer and winter begins to rise in 1990 s,except autumn rises in 1980 s.Since 21 st century the rising trend is more obvious,and the warm rate of winter is highest.Extreme minimum temperature also has a rising trend.Annual extreme minimum temperature and the temperature of spring and summer increase from1990 s,but autumn and winter extreme minimum temperatures increase from 1980 s and 1970 s.Extreme maximum temperature appears a rising trend.The temperature of spring and autumn has reached record value in 2006,meanwhile,there is a worst drought in Chongqing.Annual precipitation is fluctuating with a slightly decreasing trend.Precipitation is decreasing in spring,summer and winter,while autumn is on the increase.There is a trend of rainy days that is becoming less at first,then becoming more,and finally becoming less.As a whole,rainy days also become less during 1955-2015.(2)The climate change of Wanzhou district has a significant abrupt change.Annual mean temperature changed from low to high in 2004.The mean temperature of autumn is same as annual man temperature.The mean temperature of winter began to change in 1997,but spring and summer had no abrupt change.There were abrupt change among annual extreme minimum temperature and the four seasons,which occurred in 1994,1992,2001,1996 and 1985.The abrupt change of annual extreme maximum temperature occurred in 2005.In seasons,the abrupt change of extreme maximum temperature in summer and autumn were in 2004,1996,while there was no abrupt change in winter and spring.According to the M-K test of precipitation,only the precipitation of autumn had an abrupt change,that changed from little to much in 1957.Annual rainy days had a decreasing abrupt change,which happened in 1996.The abrupt change of rainy days in autumn and winter happened in 1977 and 1957.However,the rainy days of spring and summer had no obvious abruptchange.(3)The climate change of Wanzhou district has various periods in multiple time scale.The main periods of annual mean temperature are 2a and 31 a.In seasons,the main periods of spring and autumn are the same,which are 2a and 7a;the main periods of summer and winter are 2a and 9a.The oscillation of annual extreme minimum is basically determined by the periods of 2a and 5a.In season,the main periods of spring are 2a,5a and 31a;the main periods of summer are 4a and 31a;the main periods of autumn are 3a and 10a;the main periods of winter are 3a and 7a.The variety of annual extreme maximum temperature is affected by the periods of 3a and 8a.In seasons,the main period of spring is 2a;the main periods of summer are 2a and 6a;the main periods of autumn are 3a and 8a;the main periods of winter are 2a and 8a.The change of annual precipitation is mainly dominated by the periods of 2a and 5a.In seasons,the main periods of spring are 4a and 6a;the main periods of summer are 2a and 9a;the main periods of autumn are 3a and 8a;the main periods of winter are 3a and 6a.The fluctuation of annual rainy days is primarily influenced by the periods of3 a and 7a.In seasons,the main periods of spring are 2a and 6a;the main period of summer is 2a;the main periods of autumn are 4a and 10a;the main periods of winter are 3a and 15 a.(4)There are obvious correlations among various meteorological factors of Wanzhou district.There are highly obvious positive correlations between annual mean temperature and extreme minimum temperature,extreme maximum temperature.There are obvious negative correlations between annual mean temperature and precipitation,rainy days.On the part of seasons,there are highly obvious positive correlations between mean temperature of four seasons and extreme minimum temperature except for summer.There are highly obvious positive correlations between mean temperature of four seasons and extreme maximum temperature except for winter.There are obvious negative correlations between mean temperature of summer and precipitation,while there are weak negative correlations between mean temperature of other seasons and precipitation.Mean temperature of four seasons have negative correlations with rainy days.There are highly obvious negative correlations between annual precipitation and mean temperature.There are obvious negative correlations between precipitation and extreme minimum temperature,extreme maximum temperature.There are highly obvious positive correlations between precipitation and rainy days.On the part of seasons,the correlations between precipitation of summer and extreme minimum temperature,extreme maximum temperature are most obvious.(5)The water storage of Three Gorges Reservoir has some effects on the climate of surrounding areas.By comparing the climate characteristics before and after water storage,it is concluded that mean temperature,extreme minimum and extreme maximum temperature are all increasing.In the four seasons,the warm rate of winter is highest,while summer is lowest.As to precipitation,annual precipitation shows a decreasing trend.Four seasons all become less except for autumn.Rainy days appear a decreasing trend.The precipitation change is in correspondence with the trend during1955-2015.In a word,the general characteristics of climate change after water storage of Three Gorges Reservoir is similar to the climate of southwest areas.But the rising speed of temperature inwinter is higher;while in summer become lower.It presents that Three Gorges Reservoir may have a few effects on the temperature of surrounding.It has increasing temperature in winter effect and decreasing temperature effect in summer.The precipitation has on significant variety after water storage.So Three Gorges Reservoir could have almost no effect on precipitation.