| Precipitation is one of the key processes of the world's water cycle.In the water cycle and atmospheric cycle process of each space-time scale,precipitation information plays a crucial role.Rainstorm and floods are very common in the rainfall of Xiangxi Autonomous Prefecture and the spatial distribution of rainfall is uneven.Therefore,the spatial rainfall information is needed to monitor the west of Xiangxi Autonomous Prefecture in real time.In this study,Xiangxi Autonomous Prefecture was used as the research area,and the daily rainfall data of surface weather stations in Xiangxi Autonomous Prefecture from 2002 to 2012 as the measured values.Through analysis methods such as coefficient of correlation,error and relative deviation,etc.,the TRMM rainfall data accuracy and deviation features were researched and analyzed from the aspect of space-time scale to provide useful spatial information.At the same time,analyzed the spatial distribution of rainfall in the study area,and rainfall data was calibrated to provide useful spatial information and theoretical support for rainfall research in Xiangxi Autonomous Prefecture.The main conclusions are as follows:1.Rainfall data accuracy analysis: The overall TRMM rainfall was slightly higher than the rainfall at the weather station.A regression equation was established,in which ground rainfall data and TRMM rainfall data were taken as independent variables and dependent variables respectively.The correlation coefficient of annual rainfall data is 0.84.The annual rainfall data at each site has a high correlation coefficient and the relative deviation is within ± 10%.The reason for the larger deviation in some areas is that the difference in elevation within the TRMM rainfall grid is large,and there is a large difference between the elevation of the station elevation and the average elevation of the grid,and the urban effect is large.The correlation coefficients of rainfall data in spring,summer,autumn and winter were0.81,0.84,0.84,and 0.81,respectively,and the relative deviations were 8.00%,3.38%,0.07%,and-30.07%.The overall accuracy of the four seasons is relatively high,and the precisions are summer> spring> autumn> winter.The correlation coefficient of the monthly rainfall data correlation coefficient reached 0.89,and there was a clear linear correlation.The average annual rainfall error at each site has positive and negative values,and the winter error in the four seasons is the smallest,and the autumn error is the largest.2.Rainfall frequency accuracy analysis: In the contribution rate of rainfall,the contribution rate of different daily rainfall to total rainfall is roughly the same.The contribution rate of precipitation in 10-25 mm and 25-50 mm rainfall accounts for a high contribution rate.In terms of rainfall occurrence rate,TRMM and the ground weather stations have the same trend of occurrence of rainfall statistics.The deviation of TRMM from the rainfall data of the surface weather stations tends to increase first and then decrease as the daily rainfall increases.3.Rainfall spatial distribution: The average annual rainfall is gradually reduced from northeast to northwest and southwest in Xiangxi Autonomous Prefecture.Therainfall in Xiangxi is mainly concentrated in spring and summer.In spring and winter,the spatial distribution of rainfall trends is relatively consistent,and the distribution in summer and autumn is relatively the same.The annual and seasonal rainfall in the area are affected by the mountain and monsoon.4.Data correction: The GDA method and the GRA method were used to calibrate the annual rainfall data of the TRMM satellites which be showed to capture a wider range of rainfall changes.It was found that the GRA method was more effective. |
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