Accuracy Assessment of Global Satellite Mapping of Precipitation (GSMaP) Product over Poyang Lake Basin, China

Abstract The purpose of this study is to evaluate the accuracy of GSMaP by using the gauge-based precipitation measurements across Poyang Lake Basin at daily, monthly and annual scales. The results show that GSMaP products generally underestimate precipitation amount. The monthly correlation coefficient is 0.85, which shows a significant linear relationship between product estimations and rain-gauged observations while the daily correlation coefficient is less than 0.50 on average. The performance of precipitation estimation based on satellite data is poorer in mountainous areas than that in flatlands. The results also show that relative errors decrease in wet months and increase gradually in dry months, while the trends of mean absolute errors (MAE) and root mean square errors (RMSE) are just opposite. In wet periods, the omission is higher but the commission is lower. However, in dry periods the situation is often opposite. The analyses also show that omission, commission and underestimation of precipitation caused the differences between validation data and remotely sensed data to some degree. The events of strong precipitation have not been detected; or even detected, the amount of the precipitation has been insufficiently estimated are the main reasons why there is a difference between remotely sensed data and validation data. Moreover the underestimation and overestimation of precipitation amount are also the major reasons.