Assessment of Satellite Rainfall Estimates as a Pre-Analysis for Water Environment Analytical Tools: A Case Study for Tonle Sap Lake in Cambodia

Abstract

Tonle Sap Lake is the second main source of water supply and food security in Cambodia. However, this area is in the need for rainfall information which can cover the entire area for an accurate hydro-hydraulic modeling, climate modeling and other types of water or environment related modeling. In this case, Satellite Rainfall Estimates (SREs) would play a major role by filling out missing data where gauge observation is not available. The study aims to assess the spatio-temporal performance of two high resolution satellite products such as TRMM 3B42V7 and CHIRPS V.2. One-hundred and fifty four (154) stations around the Tonle Sap Lake and some close to the Mekong River were selected for the analysis within the study period of 2000 to 2004. After this, proper bias correction method is proposed. To do this, GIS and statistical indicators were used for the comparison. Both TRMM and CHIRPS provide a good correlation with the gauge. Around 90% of stations have CC varies from 0.5 to 0.9. In addition, the median bias of SREs are about 30 mm/month. Both satellite showed very similar pattern of bias spatially and temporally. This can be said that even though TRMM has the lower spatial resolution compared to CHIRPS, the performance of it is better. Moreover, TRMM have higher correlation when each of its cells was compared with the averaging of all stations within that cell. 25% of data that have extreme bias ratio maybe due to other underlying factors such as the distance from the station to the city, the soil elevation, landuse type, age of instrument, occurring of storm or drought that need to be taken into account for the further study.