Rainfall statistics evaluation of ECMWF model and TRMM data over Bangladesh for flood related studies

Quantitative precipitation estimates from the European Centre for Medium-Range Weather Forecasts (ECMWF) modelling system and the Tropical Rainfall Measuring Mission (TRMM) may be used for areas where rainfall data are not available or where the number of rainfall stations is inadequate. In this study, ECMWF 40 years re-analysis (ERA40) and TRMM satellite estimated daily rainfall data have been analysed at three station locations, Dinajpur, Rangpur, and Sylhet, in the Bangladesh territories of Ganges, Brahmaputra and Meghna basins, respectively. Statistical verifications (visual verification, yes/no dichotomous verification and continuous variables verification methods) have been applied to these data. Bangladesh Meteorological Department (BMD) rainfall data are used as the reference data. The continuous variables verification methods show the better accuracy of the TRMM data. The probability of occurrence of TRMM rainfall is close to the BMD-observed data. It implies that the TRMM data can be used for modelling of design flood in areas where observed rainfall data are not available. However, in the case of the TRMM rainfall data, the chances of missing a flood event are higher compared to the ECMWF data. Yes/no dichotomous verification methods show that ECMWF rainfall data are safe to use for flood-forecasting-related planning purposes because rain events are estimated better in ECMWF. The probability of occurrence of ECMWF rainfall shows that these data can also be used to estimate the design flood flow. Both ECMWF and TRMM rainfall data may be used where locally observed rainfall data are not available. Copyright © 2011 Royal Meteorological Society