Comparison of traditional method and triple collocation analysis for evaluation of multiple gridded precipitation products across Germany

Abstract Evaluating the accuracy of precipitation products is essential for many applications. The traditional method evaluation to calculate error metrics with gauge measurements that are considered as ground-truth. multiplicative triple collocation (MTC) has been demonstrated powerful in quantification when ground-truth not known. This study applied MTC evaluate five Germany: two raw satellite-based (CMORPH and PERSIANN), one reanalysis (ERA-Interim), soil moisture-based (SM2RAIN-ASCAT), gauge-based (REGNIE) products. Evaluation was performed at 0.5° -daily spatial-temporal scales. involves a log transformation data, necessitating dealing zero values daily precipitation. Effects 12 different strategies value on results were investigated. Seven triplet combinations tested stability MTC. Results showed replacing had considerable effects MTC-derived particularly root mean squared (RMSE). generated individual correlation coefficient (CC) more reliable than RMSE. It appropriate use compare relative Based CC unknown truth, produced same ranking method. A comparison from classic TC additive model potential limitation arid area or dry time periods large ratio