A Study On Accuracy Evaluation Of Various Precipitation Products And Their Applicability For Drought Monitoring In Different Subregions Of China

The instability of the temporal and spatial distribution of precipitation is the direct factor that causes natural disasters such as drought and flood.To monitor drought and flood disasters more accurately,a high-quality precipitation data set with high temporal and spatial resolution is required.In recent years,a variety of grid precipitation products have been produced around the world,and based on their data sources and calculated methods,they can be roughly divided into three categories: ground-station-based,satellite-based,and reanalysis precipitation products.Accuracy characteristics are of great significance to its accurate application and development.In addition,drought is the most serious and frequent natural disaster that causes economic losses.Therefore,it is of great significance to study the drought monitoring performance of different types of precipitation products.This article evaluated the latest version of IMERG precipitation products based on meteorological sites,and compared it with the delisted TMPA precipitation products and corrected them.In addition,it also analyzed and compared nine sets of precipitation products based on different types in various regions of China.And explored their performance differences in different months.Finally,based on the Z index and SPEI indicators,we explored the drought monitoring performance of different precipitation types.The main conclusions obtained in the paper are:(1)The IMERG V6 outperformed the delisted TMPA precipitation product,and it could be corrected by linear regression relationship.At the daily,monthly and yearly time scales,the accuracy of IMERG V6 precipitation product is higher than that of TMPA,and the accuracy increases with the expanding time scale.IMERG V6 product performed better than TMPA product in China's mainland and all subregions.Among them,the performance of IMERG V6 product is the best in the mid-temperate semi-humid region and the worst in the mid-temperate dry region.In addition,in most subregions of China,IMERG V6 product is more accurate in estimating precipitation than TMPA products,but in the dry(December,January,and February)and humid(July,August,and September)months,the performance is poor.The linear relationship between remote sensing products and ground observation precipitation can be used to correct satellite precipitation data without using the latest gauge-based data from weather stations.The corrected IMERG V6 precipitation data has good spatial variability and higher accuracy than the original IMERG V6 data.(2)According to the precipitation characteristics and accuracy performance of different types of precipitation products in China,the products with strong comprehensive applicability are GPCC,IMERG V6,and MSWEP.The performance of different types of precipitation data sets varied in different subregions and China's mainland.In the northwest desert subregion and the Qinghai-Tibet Plateau subregion,the overall performance of all precipitation products is the worst among all subregions.According to mutiple precipitation characteristics,all precipitation products performed differently.The accuracy of different types of precipitation products varies significantly from January to December.In most subregions,satellite-based and reanalyzed precipitation products have poor accuracy respectively in winter months and drier areas,and in summer months and relatively humid areas.The accuracy of gauge-based precipitation products is less affected by months.In summary,satellite-based precipitation products have more advantages in analyzing the spatial variability of precipitation,and precipitation data sets based on ground stations have a stronger ability to capture temporal variability of precipitation.Among the satellite-based,ground-based and reanalyzed precipitation products,the products with the stronger comprehensive advantages are IMERG(MSWEP),GPCC and MERRA.(3)To dig out the drought monitoring performance of different types of precipitation products from the perspectives of the estimation accuracy evaluation of the drought index based on different types of precipitation products,and the time analysis and spatial analysis of drought monitoring based on the precipitation products.Comparing the estimation accuracy of drought indicators for different types of precipitation products,IMERG and MSWEP/GPCC precipitation products have stronger estimation accuracy for the Z index and SPEI indicators respectively.Comparing the two drought indexes,most precipitation products have a higher estimation accuracy of the SPEI index than the Z index.Comparing different districts,the estimation accuracy of Z index and SPEI index for most precipitation products in districts 1,3 and 3,7 is relatively poor.The accuracy of drought index estimation based on different types of precipitation products is different in sensitivity to time scale.The estimation accuracy of drought index based on reanalysis products is most susceptible to the influence of time scale,and decreases as the time scale increases.The SPEI-based time series can capture historical drought events more accurately than the Z-index.The satellite-based precipitation products are generally stronger than other precipitation products in estimating the two drought index time series in each study area.The accuracy of the drought area estimated by SPEI for different types of precipitation products is greater than the Z index,and GPCC products have always been the best choice.The main drought period estimated based on the Z index is lower than the main period estimated based on SPEI.The spatial distribution of drought based on SPEI monitoring is higher than the Z index in terms of intensity and area,but more products based on the Z index have better drought monitoring accuracy than SPEI.The most suitable precipitation product for calculating the spatial distribution of the Z index is IMERG,and the most suitable precipitation product for calculating the SPEI index and monitoring the spatial distribution of drought conditions is MSWEP.In the monitoring of drought events,the number,duration,and intensity of drought events monitored by the Z index in China's mainland are slightly lower than SPEI.The two drought indicators are similar in sensitivity to precipitation products in monitoring drought events.The most suitable precipitation product for the Z index to estimate the drought events,duration,and intensity is the PERSIANN-CDR or GPCC precipitation data set,while the SPEI index is used to estimate the drought events and duration.The best choice for intensity is GPCC or MSWEP precipitation products.