Abstract
Satellite-based precipitation is an essential tool for regional water resource applications that requires frequent observations of meteorological forcing, particularly in areas that have sparse rain gauge networks. To fully realize the utility of remotely sensed precipitation products in watershed modeling and decision-making, a thorough evaluation of the accuracy of satellite-based rainfall and regional gauge network estimates is needed. In this study, Tropical Rainfall Measuring Mission (TRMM) Multi-Satellite Precipitation Analysis (TMPA) 3B42 v.7 and Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) daily rainfall estimates were compared with daily rain gauge observations from 2000 to 2014 in the Lower Mekong River Basin (LMRB) in Southeast Asia. Monthly, seasonal, and annual comparisons were performed, which included the calculations of correlation coefficient, coefficient of determination, bias, root mean square error (RMSE), and mean absolute error (MAE). Our validation test showed TMPA to correctly detect precipitation or no-precipitation 64.9% of all days and CHIRPS 66.8% of all days, compared to daily in-situ rainfall measurements. The accuracy of the satellite-based products varied greatly between the wet and dry seasons. Both TMPA and CHIRPS showed higher correlation with in-situ data during the wet season (June–September) as compared to the dry season (November–January). Additionally, both performed better on a monthly than an annual time-scale when compared to in-situ data. The satellite-based products showed wet biases during months that received higher cumulative precipitation. Based on a spatial correlation analysis, the average r-value of CHIRPS was much higher than TMPA across the basin. CHIRPS correlated better than TMPA at lower elevations and for monthly rainfall accumulation less than 500 mm. While both satellite-based products performed well, as compared to rain gauge measurements, the present research shows that CHIRPS might be better at representing precipitation over the LMRB than TMPA.
Highlights
Precipitation is one of the most important features in the global water and energy system and is vital to effective hydrology and climate research [1]
The hydrologic significance of TRMM Multi-Satellite Precipitation Analysis (TMPA) and CHIRPS in the Lower Mekong River Basin (LMRB) could be assessed from the results of this study and other analogous validation studies
A similar methodology to the one described here could be applied to the Global Precipitation Mission (GPM) Integrated Multi-Satellite Retrievals for GPM (IMERG) data to further assess the performance of satellite-based precipitation products in the region
Summary
Precipitation is one of the most important features in the global water and energy system and is vital to effective hydrology and climate research [1]. The Lower Mekong River Basin (LMRB) in Southeast Asia is susceptible to precipitation-based natural disasters and is heavily dependent on proper water resource management to adequately sustain the more than 60 million inhabitants in the region whose livelihoods depend on the food and agriculture provided by the Mekong River and its many tributaries [2]. The Mekong River is considered the tenth largest river in the world based on discharge and length [3]. In this region, rainfall seasonality causes droughts and floods that can negatively affect local resources associated with fishing and farming [4]. Precipitation in the lower basin follows an east to west gradient with the highest annual rainfall accumulation (3000 mm) occurring in the uplands of Laos and Cambodia and the least accumulation (1300 mm) occurring in northeast Thailand [4]
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