Downscaling Method And Spatial Variability Of Precipitation In Tianshan Mountain Based On The TRMM Date

With the development of science and technology, remote sensing is widely applied in hydrologicalresearch. The precipitation data from TRMM has become a popular remote sensing data. TRMM isregarded as a high accurate precipitation data. However, the data’s spatial resolution is insufficient in thequalitative relationship analysis between The characteristics of spatial variation in precipitation andelevation, slope, slope direction We studied the downscaling method for high spatial resolution andfurther used in the spatial variation analysis of precipitation in Tianshan mountion. This study hold greatsignificance for hydrological research in mountainous watershed.In this study, the author verified the applicability of TRMM precipitation data in Tianshanmountains with measured data of site in study area and remote sensing images in Tianshan MountainsUsing downscaling method which based on NDVI obtained Surface precipitation figure with higherspatial resolution. The author analyzed the spatial variation characteristics of the precipitation and itscause combined with the local topography and atmospheric circulation characteristics in Tianshanmountain. The conclusions are as follows:(1)TRMM precipitation data is applicable to Tianshan mountain. The correlation coefficientbetween observation data and TRMM precipitation data has reaches above0.7after correction, and therelative error was in the allowable range. The shorter the time length the more accurate The TRMM datawas and the heavier the rainfall the more accurate the TRMM date was.(2)Downscaling method based on NDVI is workable. We explored the relation between precipitationestimates derived from the TRMM and the NDVI, using time series from2000to2010. The result showedthat, the correlation coefficient between downscaled TRMM data and observation data increased to0.80,the bias decreased to0.10, and the root mean square error become62.33and60.12. The data’s was moreaccurate with quadrature method than summation method.(3)The spatial variation of precipitation has following characteristics in Tianshan mountain. Theprecipitation reduce gradually from west to east, and the precipitation of the northern slope is slightlyhigher than south.(4) The precipitation distribution is related to terrain factors in Tianshan mountain. Rainfall isincreased with the rise of elevation and then declined to a certain altitude. Rainfall is increased with therise of elevation when the slope is less than45°and the smaller the slope the less precipitation change,on the contrary, the precipitation decline when the slope is greater than45°. The same rules hold true forwindward slope.(5)The cause of spatial variation of precipitation based on topographic factors is the orographydynamic lifting.