资源环境科技发展态势分析平台

With increasing spatiotemporal resolution and accuracy, satellite-based precipitation estimations (SPEs) have become critical data sources for hydrological applications. Their global scale coverage and short latency perfectly fit the requirements of flood forecasting. However, the comprehensive evaluation of the latest generation of SPEs is an essential step before the confident use of these indirect precipitation estimators. Therefore, the latest releases of the Integrated MultisatellitE Retrievals for Global Precipitation Measurement (IMERG) Version 5 products, including the near-real-time "Early" run and "Later" run products (IMERG-E and IMERG-L, respectively), and the post-real-time "Final" run IMERG product (IMERG-F), are employed in this paper. Through the hydrometeorological assessment of these three IMERG products against dense gauge observations during the period from April 2014 to December 2015 over the Upper Huaihe River Basin (UHRB), the usability of IMERG products in hydrological application is explored via the Variable Infiltration Capacity model. The results indicate that, irrespective of a slight positive bias, the post-real-time IMERG-F product presents the best performance among the three IMERG products at both the grid scale and basin scale. Although all three IMERG products show remarkably high probability of detection (POD, approximately 0.82), the IMERG-E presents a relatively higher false alarm ratio (FAR = 0.37) in comparison with IMERG-L (FAR = 0.32) and IMERG-F (FAR = 0.31), which is primarily due to the significant overestimation in light rain events. In terms of hydrological simulations of streamflow, the dense gauge observations exhibit very good performance for both entire simulation period and flood events, as expected. IMERG-F demonstrates acceptable performance in entire simulation, while both IMERG-E and IMERG-L demonstrate poor performance. Given the clear overestimation in short-terms flooding and the notable underestimation in long-terms flooding, all three IMERG products should be used with caution in flood simulation over UHRB. Overall, this is a systematic assessment of IMERG products. We hope this study can provide useful guidelines for potential hydrologists of IMERG products and further IMERG algorithm development. Also, given the scope of on-going efforts to improve the IMERG products, we believe the subsequent versions of IMERG can be widely used in global or regional hydrological application, particularly in the field of flood forecasting.