Analysis Of Drought Variation Characteristics And Disaster Risk In The North China Plain Based On Multiple Drought Indice

The drought caused by climate change has brought many disasters to mankind.The global economic loss caused by drought is about 6—8 billion US dollars every year.China is a large agricultural country,and drought is the main restrictive factor affecting the agricultural economy.As one of the most serious natural disasters in China,drought is increasingly threatening China’s food security and ecological security and restricting the development of the national economy.In this paper,four remote sensing drought indices,Crop Water Stress Index(CWSI),Drought Severity Index(DSI),Normalized Vegetation Supply Water Index(NVSWI)and Temperature Vegetation Drought Index(TVDI),were used to explore their relationship with soil relative humidity in different temporal and spatial scales;Based on Standardized Precipitation Evapotranspiration Index(SPEI)and typical drought events,the applicability of each drought index was evaluated;Based on the optimized drought index(CWSI),the temporal and spatial distribution and variation characteristics of drought in North China Plain and its relationship with climate indices and meteorological factors were analyzed;The temporal and spatial variation of drought disaster risk and the combined disaster risk of drought and high temperature in North China Plain were evaluated.The main conclusions are as follows:(1)in temporal and spatial scales,the correlation between CWSI and soil relative humidity in North China Plain was the highest,and each season showed a relatively synchronous change trend.From the correlation,root mean square error and standard deviation with SPEI,CWSI was outstanding.In addition,CWSI had good monitoring effect on some major drought events.(2)From 2000 to 2018,the drought intensity of North China Plain showed an increasing trend in all seasons(0.02—0.08)/10 a except spring(-0.04/10 a).The drought frequency had an increasing trend in all seasons(0.13—1.74%)/a.And the drought coverage area ratio showed a slow increasing trend(0.49—2.80%)/a except spring.The whole region was dry in the north and wet in the south.(3)Spatially,the correlation coefficient between average precipitation and CWSI was-0.41(P<0.05).The high value area was mainly concentrated in Henan and Shandong Province,and had passed the significance test of 0.05 level.In time,the correlation between precipitation and CWSI was higher,and the correlation coefficient especially in autumn was as high as-0.78(P<0.01),indicating that precipitation had a greater impact on drought.(4)Among the 19 climate indices,Western Hemisphere Warm Pool(WHWP)and Atlantic Multidecadal Oscillation(AMO)had the largest positive correlation with CWSI,reaching 0.62.The negative correlation between East Atlantic Western Russia(EAWR)and CWSI was the largest,which was-0.61.It can be seen that WHWP,AMO and EAWR were the main climate indices affecting drought.(5)From 2000 to 2018,the risk of drought disasters in the North China Plain showed an insignificant increasing trend.Spatially,the risk of cities in the south was gradually increasing,with a growth rate of 0.13/10 a,while the risk of some areas in the north was not significantly reduced.(6)From 2000 to 2018,the frequency and intensity of high temperature and heat waves in North China Plain gradually increased,with the rates of 0.02 times/a and 0.10℃/a respectively.The frequency of high temperature heat waves increased in cities of Henan Province in the west,Dezhou,Jinan and Heze in Shandong,while decreased significantly in Shijiazhuang in Hebei(P<0.05).The frequency and intensity of high temperature heat wave in summer did not increase significantly with the rate of 0.03 times/a and 0.16℃/a respectively,and concentrated in Henan,Shandong and other places in the west and south,and reached a significant increase level in Zhengzhou and Xinxiang(P<0.05).(7)The risk of combined disaster caused by drought and high temperature wave in summer in North China Plain showed no significant increasing trend,with a growth rate of about 0.01/10 a.The risk of drought and high temperature heat wave disasters in Henan cities in the southwest,Northern Anhui and Jiangsu and southern Shandong showed an increasing trend,with a maximum rate of 0.14/10 a.The risk of drought disaster in the western region was low,but the risk of combined disaster was high,and the growth rate was greater,which was easy to be ignored in the disaster prevention and reduction strategy,and should be paid attention to.