| As an indispensable meteorological element in human life,precipitation is an important driving factor in the fields of climate meteorology,agriculture,hydrology,etc.The TRMM satellite rainfall data has been widely used in research because of its high spatial resolution and wide coverage.However,for small watersheds such as the Nanliu River,its spatial resolution of 0.25° still cannot meet the needs.And the quality of the data directly affects the results of the model simulation.Therefore,this paper takes the data of TRMM 3B43 in the Nanliu River Basin as the research object,and conducts spatial downscaling and hydrological application research.Firstly,the accuracy of 0.25°TRMM rainfall data is evaluated,using the measured rainfall data of 16 rainfall stations in the Nanliu River Basin,and then the geographic weighted regression(GWR)model is established by introducing vegetation NDVI data,and the spatial downscaling to 1km is carried out.Then the geodetic difference analysis(GDA)calibration is performed on the downscaled TRMM data,and the accuracy of the data after downscaling calibration is verified;Finally,the 0.25° and 1km TRMM rain data and the measured rainfall data are respectively applied to the SWAT distributed hydrological model.The accuracy and application performance in SWAT model runoff simulation of the TRMM rainfall data,and the applicability of downscaling calibration method are indirectly verified by comparing and analyzing the runoff results obtained by different rainfall data driven models.The main conclusions are as follows:(1)The overall correlation coefficient(CC)of monthly,seasonal and annual 0.25°TRMM data is 0.86,0.89 and 0.69,respectively,and the accuracy is high.Individual accuracy evaluation of other sites are higher except for individual stations,such as Bobai Station,of which the accuracy is relatively low and spatial characterization is weak.In general,the 0.25°TRMM correlation coefficient,relative error and root mean square error are better controlled,with higher precision and good applicability.(2)Compared with the 0.25°TRMM rainfall data,the overall correlation coefficient(CC)of the 1km TRMM annual precipitation data based on the GWR regression model downscaling and the GDA method was increased from 0.69 to 0.98,the root mean square error(RMSE)and the relative error absolute value(BIAS)was reduced from 346.24 and 4.42%to 116 and 3.06%,respectively,and the accuracy evaluation results and spatial characterization ability were improved.(3)According to the SWAT hydrological model evaluation standard,it is obtained that all three rainfall data can be applied to the simulation of daily and monthly runoff in the SWAT hydrological model of the Nanliu River basin.Moreover,the lkmTRMM rainfall data of downscaling and calibration has the best simmulation result and the highest applied value,because it combines the advantages of surface rainfall data from satellite and single-point rainfall data from rain gauge station.That indirectly verifies the accuracy of lkmTRMM rainfall data of downscaling and calibration can be improved and the method of downscaling and caluibration is applicable in Nanliujiang River Basin. |
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