Spatial And Temporal Evolution And Applicability Analysis Of Drought In Jiangsu Province Based On Different Drought Indices

Being harmful to agricultural production,meteorological drought could develop into agricultural drought,which is impacting the growth of rice and wheat seasonally in Jiangsu province.It is the premise and base for agricultural,hydrological and socioeconomic drought.Therefore,timely and accurate monitoring of meteorological drought is of great significance to agricultural production and social development,as well as the prevention and reduction of natural disasters.In this study,Jiangsu was divided into three regions: northern Jiangsu,central Jiangsu and southern Jiangsu.Basedon the daily rainfall and reference crop evapotranspiration data of 60 stations from 1961 to 2018,this paper selected standaradized precipitation evapotranspiration index(SPEI),standaraized precipitation index(SPI),relative moisture index(MI),Zindex of precipitation(Z)and percentage of precipitation anomalies(Pa)to study the drought spatial and temporal variation characteristics in Jiangsu Province.The results are as follows:(1)The timely variations of precipitation were mainly manifested in the trend of increasing from 1961-2018 with a mean rate of 3.36mm/a,and decreasing gradually from southeast to northwest.The monthly variation indicates that Jiangsu had obvious dry and wet seasons,more precipitation(6,7,8)in summer with a proportion of 50.24% of the total rainfall all the year round,and less precipitation(11,12,1)in winter with a proportion of 9.36% throughput the year.For spatial distribution,annual precipitation was in a decreasing from southeast to northwest,the difference value between Yixing,located in the southernmost and Fengxian,located in the northernmost was 533.577 mm.And the precipitation in southern is often more than 1000 mm.(2)The interannual variation characteristics of potential evapotranspiration(ET0)were mainly manifested in the upward trend from 1961-2018,with an average increase rate of 6.40 mm/10 a.The rising trend in southern Jiangsu was the most significant,with a rising rate of 9.31 mm/10 a,and the lowest rate in middle with a rising rate of 0.76mm/10 a.At the beginning of the 1970s-2000 s,the trend was basically downward,and then the south,middle and the total province began to rise,the downward trend of the north began to slow down.In terms of the variation characteristics of monthly average potential evapotranspiration,the three regions were all the lowest in January and the highest in July,with the mean value of 29.46 mm and 117.25 mm,respectively.The monthly average protentional evaportranspiration was the highest in south,and lowest in northern Jiangsu,the difference between south and central was not significant,but obvious between south and north.(3)The drought frequencies calculated by the five drought indices had an order of Pa>MI>SPEI>SPI>Z,and there was a big difference between maximum and minimum with the highest value of 17161 and the lowest value of 9776.The annual variation trend of the total frequencies of drought was relatively consistent among the 5 indices,while the monthly average varied greatly with the alternation of months.The frequencies from SPEI,SPI and Z stabilized from January to December,MI and Pa distributed like a "V" word from January to December,with a decline from January to June and an increase from July to December.The frequencies from Pa were in a range of 40-50 both in January and December,but they were less than 10 in June and Junly.(4)The variation trend of five drought indices values was more consistent in representing stations in the three areas.Among which,the consistency between SPEI and SPI was high,as well as MI and Pa.In the correlation analysis,the correlation of five indices in the representative station of southern Jiangsu was higher,followed by northern Jiangsu,and there were 6 groups of indices in central Jiangsu without correlation.The correlation between SPEI and SPI was relatively high in Jiangsu Province and the correlation coefficients varies between 0.94 and 1.00.All the correlation indices passed the significance test of 0.001.(5)The adaptability evaluation of drought index in Jiangsu Province was analyzed according to typical drought year and drought area and detailed drought process record site.The results were shown that among the five drought indexes,the optimum index of Jiangsu Province was first SPEI,second MI,but other indices had good adaptability at certain times.