Evaluation and Comparison of Daily Rainfall From Latest GPM and TRMM Products Over the Mekong River Basin

Many satellite-based precipitation products have been developed and released during the past decades. This paper presents a primary evaluation and comparison of the two latest products, the Global Precipitation Measurement (GPM) mission Level 3 product Integrated Multi-satellitE Retrievals for GPM (IMERG) and Version 7 Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) products. The comparison is based on daily scale data from April 1, 2014, to January 31, 2016, over the entire Mekong River Basin (MRB). Daily observation data from 53 rain gauge stations were obtained to carry out a pixel-point comparison. Various aspects were taken to examine the performance of these two satellite-based precipitation products. The results demonstrate the following: 1) Both IMERG and TMPA overestimate the amount of rain when the rain is light (less than 8 mm at daily scale), and underestimate when the rain is heavy (more than 14 mm at daily scale), and IMERG performs better than TMPA, particularly for reducing the overestimation of light rain; 2) in term of event detection, IMERG more accurately detects rainfall events than TMPA, especially for slight rainfall; 3) IMERG reproduces the probability density function (PDF) of precipitation intensity and captures its intra-annual variability better than TMPA, especially in the Lower Mekong Basin; and 4) both products still have potential for further improvement, particularly applications during the dry seasons and in high-latitude/mountainous regions. This study provides useful information on efficiently deploying IMERG to hydrological studies and for improving IMERG algorithms.