Accuracy Evaluation And Comparison Of GPM IMERG V5 And TRMM 3B42v7 Precipitation Product In The Yangtze River Basin

Accurate precipitation estimation is essential to the hydrological simulation,climate monitoring,and disaster prevention.The use of satellite-based precipitation products?SPPs?,as a completely new technology,not only makes up the limitation of the observation of radar and ground gauges,but also makes it possible to detect the rainfall in the ungauged areas.The purpose of this study is to quantitatively assess the accuracy of the GPM IMERG version 5 and the TRMM 3B42 v7,with the reference of 224 ground rain gauge stations in the Yangtze River basin in China from April 2014 to December 2017.Some research methods,such as kriging interpolation method,bilinear interpolation method,contingency table method and so on were employed to investigate the accuracy of two SPPs at different spatiotemporal scales,different altitudes and different monsoon regions.The results showed that:?1?For temporal comparison,GPM and TRMM both showed the lowest accuracy in detecting daily precipitation,but the higher accuracy was shown when reproduced annual and monthly precipitation;two SPPs showed a small magnitude of overestimation?RB<6%?at three time scales;two SPPs underestimated the precipitation in winter months significantly and had large RMSE value in summer months,especially for the estimation by GPM in the lower reaches?RMSE>2 mm/d?;GPM and TRMM both had a better performance in retrieving weak rainfall thresholds than heavy precipitation.In general,GPM product had a worse accuracy in detecting precipitation at daily scale,but it was better at detecting monthly and annual precipitation.?2?For spatial comparison,GPM overestimated the annual precipitation in the lower elevation areas,whereas TRMM underestimated the precipitation in the Sichuan basin significantly;GPM tended to overestimate the range and intensity of main rain band in different months,while TRMM underestimated the precipitation in the Sichuan basin from November to February,next year;large errors were shown when retrieving the spatial distribution of P?1mm/d for both SPPs,but the good detection accuracy was exhibited when 1 mm/d<P?50 mm/d.Two SPPs both overestimated the P_PDFcDFc in the lower reaches;the MAE,RMSE and R value for two SPPs in upper stations were both lower than lower stations.?3?For the comparison at different altitudes,two SPPs overestimated the precipitation when ASL<3000 m,while the opposite was true for ASL?3000 m(RB_GPM=-5.42%,RB_TRMM=-1.87%).The accuracy of GPM was more accurate due to higher R,lower MAE and RMSE at different altitudes compared with TRMM product;GPM had higher values of POD and FAR in terms of precipitation threshold of 1mm/d,and the BIAS of GPM was near to the perfect value?1?;the results of P_PDFcDFc and average precipitation at different thresholds for GPM was closer to observed value.?4?The formation mechanism of the East Asian monsoon and the South Asian monsoon is different;the start of the South Asian monsoon was laterer than the East Asian monsoon;two SPPs overestimated the average precipitation during summer,especially in the East Asian monsoon region;two SPPs both had a higher R,RMSE,MAE and RB value in the South Asian monsoon region,and TRMM outperformed GPM in two monsoon regions which may due to the difference of algorithm.To evaluate the applicability of different SPPs is always a hot topic in the field of hydrology and remote sensing,but the prevailing problem is that these researches are not sufficient and thorough enough to give a reliable prospective in practical applications.For this reason,in this study,we detailed the performance of SPPs at different spatial and temporal scales in the Yangtze River Basin,besides,the estimation accuracy at different altitude and in the summer monsoon seasons were also included.We look forward this paper can provide a valuable reference for the further study in eco-hydrology field in this region.