The Relationship Between Precipitation Change Characteristics And Runoff In The Hotan River Basin Based On TRMM Data

As a basic component of global surface material exchange,energy cycle,ecosystem and hydrological cycle,precipitation is a key parameter in the research fields of climate,hydrology and meteorology.The traditional precipitation data mainly come from surface meteorological stations,but the sites are not adequately deployed in high-altitude area.For mountainous area with no data or lack of data,revealing the characteristic of precipitation change is particularly important for promoting regional economic development and rational allocation of water resources in the basin.In addition,for the arid region of the northwest China(ARNC),precipitation in mountainous area is an important source of supply for surface water and groundwater.Change in precipitation characteristic has an important impact on runoff change and regional water recourses.The response of river runoff to global climate change is closely related to change in precipitation,especially in arid region.Therefore,analyzing the spatiotemporal variation and influencing factors of precipitation in mountainous area in the typical watershed of the arid area,defining the relationship between precipitation and runoff have practical guiding significance for understanding the climate background of the mountain and revealing the hydrological cycle and hydrological process in the arid area.This paper takes the data-scarce mountainous area,the Hotan River Basin,as the research object.Firstly,the GRA(Geographical Ratio Analysis)calibration method is used to correct the TRMM(Tropical Rainfall Measuring Mission)3B43 precipitation data by combining the measured site data in the study area.Secondly,the characteristics and differences of precipitation in different elevation area such as low mountainous area,middle mountainous area,high mountainous area and extremely high mountainous area are analyzed,and their effects on precipitation change in Hotan River Basin are analyzed from the aspects of geographical factors and circulation factors.Finally,the relationship between precipitation and runoff in the Hotan River Basin is analyzed,and the impact of precipitation change in mountain area on runoff change is quantitatively evaluated.The findings are as follows:(1)The GRA calibration method is used to correct the precipitation data of the TRMM3B43 in the Hotan River Basin from 1998 to 2015 on the monthly and annual scales.On the monthly scale,during the calibration period(1998-2010),there is a large error between the TRMM monthly precipitation data and the measured site precipitation data before the correction,especially at the extreme point,the result is significantly different.The precipitation data after GRA correction are basically consistent with the trend of the measured site data.The correlation coefficient between the TRMM correction data and the measured precipitation in each month increased significantly,ranging from 0.86 to 0.99,and both pass the 0.001significance level test.During the verification period(2011-2015),the corrected TRMM monthly precipitation data and the measured site precipitation data are basically consistent in the time series,and the correlation coefficient between the TRMM data and the measured precipitation data in each month is above 0.80(P<0.001).On the annual scale,during the calibration period(1998-2010),the correlation coefficient between the TRMM data and the measured site precipitation data is 0.56(P<0.001)before the correction,and the correlation coefficient reaches 0.94(P<0.001)after correction.At the same time,the|BIAS|and RMSE index values are reduced by 50%and 16.79%respectively.During the verification period(2011-2015),the correlation coefficient between the TRMM data and the measured precipitation data reaches 0.95(P<0.001).The results show that the GRA method is applicable to the correction of TRMM precipitation data in the study area,and the corrected results basically reflect the true variation characteristics of precipitation in the Hotan River Basin.(2)The variation characteristics of precipitation in the Hotan River Basin at different spatiotemporal scales are studied in depth.From the perspective of time variation,the annual mean precipitation in the Hotan River Basin decreases from 1998 to 2015,and the rate is-2.25mm/10a,but this tendency does not pass the significance level test of P<0.05.The precipitation in spring and autumn shows a decreasing trend and the change is obvious(the rates are-1.19mm/10a and-2.77mm/10a,respectively),while the precipitation in summer and winter is the upward trend and the change is small(the rates are 0.25mm/10a and 0.22mm/10a,respectively).From the perspective of spatial distribution,the annual average precipitation in the low and middle mountains of the region is small(67.31mm and 112.88mm,respectively),and the annual average precipitation in the high mountains and extremely high mountains is large(167.56mm and 197.98mm,respectively).The spatial distribution characteristic of precipitation gradually decreases from south to north.From the perspective of spatial variation,the precipitation decreased area of spring and autumn in the Hotan River Basin accounts for more than 80%,and the precipitation in the low mountain area is the most stable(rates are-0.10mm/10a and 0mm/10a,respectively).Precipitation variation rate of extremely high mountain area is maximum(-1.10mm/10a and-1.70mm/10a,respectively).Precipitation rising area of summer and winter is more than 60%in Hotan River Basin,the precipitation change both are the most obvious in the middle mountain area(-0.90mm/10a and 0.09mm/10a,respectively).The extremely high mountainous area of summer(0.33mm/10a)and the low mountainous area of winter(-0.01mm/10a)are the regions with the lowest average change rate.(3)The impact on precipitation change in the Hotan River Basin is analyzed from the perspective of geography and circulation factors.Longitude,latitude and altitude contribute significantly to annual and seasonal precipitation,which are the main factors affecting precipitation variation in the Hotan River Basin.The slope mainly affects spring and summer precipitation,while the sloping direction has less impact on precipitation in each season.Among them,annual precipitation increased by 5.96mm on average per unit longitude,and the longitude has the greatest impact on summer precipitation.Annual precipitation increased by1.19mm on average per unit latitude,summer precipitation is also the most sensitive to latitude change.For every 100m increase in altitude,the annual precipitation increases by nearly 3.3mm on average,and the increase of summer precipitation with the increase of altitude is the largest,and the increase rate is 1.8mm/100m.In addition,circulation factors also have a certain impact on summer precipitation in the Hotan River Basin.Among them,the summer precipitation has the highest correlation with the Asian region polar vortex intensity index,and the correlation coefficient is as high as 0.63(P<0.001).Secondly,the correlation with the East Asian trough strength and sunspots,the correlation coefficients are-0.55 and 0.52,respectively(P<0.01).The correlation with the polar vortex area index of the Northern Hemisphere also reached a significance test at P<0.05,with a coefficient of 0.47.(4)From 1998 to 2015,the annual runoff of the Hotan River Basin shows a fluctuating upward trend with a rate of 11.21×10~8m~3/10a(P<0.05).Runoff in all seasons shows an upward trend,and the trend of runoff in summer is the most obvious,which reaches 6.09×10~8m~3/10a.The runoff in summer is maximum,at a rate of 34.11×10~8m~3,accounting for 70.54%of the whole year,especially in July and August.Followed by spring and autumn,the annual mean runoff is 5.01×10~8m~3 and 6.53×10~8m~3,accounting for 10.37%and 13.50%respectively;the rate is 2.11×10~8m~3/10a and 1.67×10~8m~3/10a,respectively.The runoff change in winter is the most stable(0.60×10~8m~3/10a),and the runoff(2.70×10~8m~3)has the least proportion,only 5.59%.Among them,the runoff is only 0.84×10~8m~3 in February.(5)There is a certain degree of synchronization between annual mean runoff and precipitation in the Hotan River Basin from 1998 to 2015,with a correlation coefficient of 0.45(P<0.05).Among them,the correlation between precipitation and runoff is the highest in the low mountain and middle mountain area,and the correlation coefficients is 0.62(P<0.05)and0.55(P<0.05),respectively.In the Hotan River Basin,only the summer average precipitation has a high correlation with the runoff(reach to 0.39),and the correlation coefficient between precipitation and runoff in low mountain area is the highest,at a rate of 0.59(P<0.05).The correlation coefficient between precipitation and runoff in other seasons is lower than 0.15,and the correlation is weak.(6)From 1998 to 2015,the sensitivity coefficient of annual runoff to precipitation change in the Hotan River Basin is 0.24.This means that 1%change in precipitation will result in0.24%change of annual mean runoff.Among them,river runoff is most sensitive to precipitation change in low mountain area,with a coefficient of 0.33;the river runoff has the almost sensitivity to the precipitation in the middle mountain area and the high mountain area,and the sensitivity coefficients are 0.26 and 0.23 respectively;the annual runoff has the lowest sensitivity to precipitation change in extremely high mountain area,and its sensitivity coefficient is only 0.11.The change in precipitation from 1998 to 2015 causes annual mean runoff in the Hotan River Basin change by-6.08%.Among them,the precipitation change in the high mountainous area causes the largest annual change rate of river runoff,which is-6.01%.The change rates of annual runoff caused by precipitation change in low mountainous area,middle mountainous area and extremely high mountain area are-3.66%,-3.62%and-3.67%,respectively.