Simulation of pre-monsoon rainfall Over Bangladesh using high Resolution wrf-arw model

Abstract

In the present study, the Weather Research and Forecast (WRF-ARW V3.5.1) model have been used to simulate the pre-monsoon rainfall during 2010–2014 for all the meteorological station points of Bangladesh. The initial and boundary conditions are drawn from the global operational analysis and forecast products of National Center for Environmental Prediction (NCEP-GFS) available for the public at 1°×1o resolution. The model is configured in single domain, 6 km horizontal grid spacing with 161×183 grids in the east-west and north-south directions and 28 vertical levels. For the simulation of pre-monsoon rainfall, WSM6-class graupel scheme coupled with Kain-Fritsch (KF) cumulus parameterization (CP) scheme has been used. Initially, the model is run 107 days for long term prediction starting with the initial condition of 0000 UTC of 17 February up to 0000 UTC of 01 June for the period 2010-2014. The model is also run for 72 hours with every day at 0000 UTC initial conditions for 94 days for the prediction of 24, 48 and 72 hours lead time rainfall in the pre-monsoon season of 2014. In this research, convective and non-convective rainfall have been simulated at 3 hourly interval then made daily and monthly total rainfall data for 24, 48, 72 hour and 107 days during the studied period. We have compared this data with the observed rainfall at 33 meteorological stations of BMD and TRMM rainfall. From this research it has been found that the 107 days predicted and TRMM rainfall is much lower than that of observed rainfall. The simulated rainfall at different stations for 24, 48 and 72 hours for the month of March, April and May are good agreement with the observed rainfall. The long term predictions of simulated rainfall are also matched with BMD observed rainfall. From the rainfall distribution the maximum rainfalls have been found in the northeastern region and also obtain in the southeastern region and the minimum rainfalls have been found in the west, northwest and southwestern regions of Bangladesh. From the rainfall distribution pattern the maximum Correlation coefficient (CC) has been shown at southern and southeastern regions and the minimum CC’s has been found in the northern, northwest and southwestern regions of the country. From this study, it has been analyzed that where the rainfall is maximum there the RMSE, MAE and CC is also maximum and vice versa. Finally, it has been observed that WRF-ARW model is suitable for the prediction of pre-monsoon rainfall.