Evaluation of gridded precipitation products in the selected sub-basins of Lower Mekong River Basin

Abstract

Hydrological and meteorological studies demand accurate, continuous, long-term, reliable, and uniformly distributed precipitation data. Considering low density rain gauges with incomplete data in developing nations, a plethora of gridded precipitation products (GPPs) have made their place as an alternative to rain gauge records. However, GPPs house inherent errors depending on the type of data, gauge density, gridding algorithm, etc. Hence, it is crucial to evaluate them prior to their application. This study evaluated monthly products of eight GPPs over 17 years (1998-2014) – Asian Precipitation Highly Resolved Observational Data Integration towards Evaluation data (APHRODITE), Climate Prediction Center (CPC), Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS), Southeast Asian Observed dataset (SA-OBS), Climate Prediction Center Morphing Technique (CMORPH), The Tropical Rainfall Measuring Mission (TRMM)-daily products, Climate Research Unit (CRU), and Global Precipitation Climatology Center (GPCC). An entropy-based weight calculation for each statistical index and compromise programming was employed to rank the GPPs in the selected sub-basins (Nam Ngum River Basin, NRB, and Vietnam Mekong Delta, VMD) of the Lower Mekong Region (LMR) for mean and six extreme precipitation indices. The correlation coefficient (r), root mean square error (RMSE), skilled score (SS), and bias were the continuous statistical indices and probability of detection (POD), false alarm ratio (FAR) and critical success index (CSI) were the categorical indices used in this study. In terms of capturing mean monthly precipitation, GPCC outweighed all other products for both the studied basins. However, APHRODITE ranked first for daily precipitation products based on compromise programming algorithm for NRB. APHRODITE consistently recorded r between 0.85 and 0.95, RMSE between 50 and 100 mm/month, and SS between 0.72 and 0.90 for the 5 observed stations. Similarly, in case of VMD, TRMM ranked first for the daily precipitation products with r between 0.8 and 0.95, RMSE between 50 and 70 mm/month, and SS between 0.56 and 0.9 when evaluated with 11 observed stations. The APHRODITE for NRB and TRMM for VMD can be used as alternate to gauge data for hydrological and meteorological studies.