Application of Satellite-based Rainfall for Operational Flood Forecasting

Abstract

The project “Application of Satellite-based Rainfall for Operational Flood Forecasting” was therefore initiated with three main objectives including 1) to assess the uncertainty associated with satellite-based precipitation estimation 2) to perform bias correction for satellite-based precipitation estimation and 3) to evaluate the performance of HAII”s flood forecasting system when bias-corrected precipitation data is used as an input to the model. This study was conducted for four river basins including the Chao Phraya River basin, the northeastern basin (the Chi and Mun River basins), and the eastern basin for the period of 2008-2015. Data used in the study included daily rainfall from telegauges of HAII, daily rainfall from the Thai Meteorological Department (TMD), and near real-time satellite-based precipitation estimation from TRMM, GSMaP and PERSIANN CCS. Uncertainty in satellite-based precipitation estimation was assessed using a set of indicators describing the capability to detect rainfall event and efficiency to capture rainfall pattern and amount. The quantile mapping method was first applied to HAII’s telegauges data to reduce uncertainty. Adjusted HAII’s telegauges data was then used to correct satellite-based rainfall estimation using the spatial bias correction method. Adjusted rainfall obtained from the final step of the correction was used as input to HAII’s flood forecasting system. Based on the evaluation of the model, satellite-based rainfall estimation contributes to an improvement in flood forecasting in all study areas. Recommendations for further study include extending the scope of the study from regional to a national level, testing the model at finer spatial and temporal resolutions and assessing other bias correction. Investing in a denser gauge network might be considered for long-term improvement.