Evaluation and application of newest GPM product with a distributed hydrological model at Mekong River basin

Abstract:

Precipitation is a key input variable for a hydrological model. In this study, the newest released satellite-based precipitation product-Global Precipitation Measurement (GPM) IMERGE data is evaluated with a distributed hydrological model-Geomorphology Based Hydrological Model (GBHM) over the Mekong River Basin(MRB), which is the most important trans boundary river in Southeast Asia. Compared with Tropical Rainfall Measuring Mission (TRMM), GPM IMERGE has a higher temporal and spatial resolution (0.1°, 30mins). Firstly, a comparison between GPM IMERGE and TRMM 3B42 is carried out at grids during 2014/3/12-10/31 at MRB. It is found that, GPM IMERGE stays quite consistent with TRMM, but GPM is more sensitive to small rainfall events especially during dry seasons, which means GPM may have a better performance in dry seasons. Then GBHM is set up and calibrated at MRB, and the model is driven by GPM IMERGE and TRMM 3B42 respectively to simulate hydrology cycle between Chiang Saen and Krait, in order to remove the influences of dam operation in upstream. The simulated streamflow is compared against the observed daily time series at five gauges on mainstream. Generally, the simulated streamflow driven by GPM is closer to observation at gauges located downstream while those driven by TRMM 3B42 have a better performance at upstream gauges. On the other hand these two results stay agreement with each other and both of them have a quite good performance with Nash-Sutcliffe efficiency higher than 0.75 and relative bias less than 10%. This study demonstrates that for daily scale application, TRMM and GPM have almost the same performance. But GPM is more promising to be applied at fine temporal and spatial scales owing to its advantage of finer temporal and spatial resolution and ability to catch small rainfall events.