Rainfall and temperature scenarios for Bangladesh for the middle of 21st century using RegCM

Regional Climate Model of version 3 (RegCM3) was driven with Emissions Scenarios A2 of ECHAM4 at 0.54°×0.54° horizontal grid resolution in two parameterizations: Grell scheme with Arakawa–Schubert (GAS) and Fritch–Chappell (GFC) assumptions. The simulated rainfall and mean surface air temperature were calibrated and validated against ground-based observed data in Bangladesh during the period 1961–1990. The Climate Research Unit (CRU) data is also used for understanding the model performance. Better performance of RegCM3 obtained through validation process, made it confident in utilizing it in rainfall and temperature projection for Bangladesh in the middle of 21st century. Rainfall and mean surface air temperature projection for Bangladesh is experimentally obtained for 2050 and 2060. This work discloses that simulated rainfall and temperature are not directly useful in application-oriented tasks. However, after calibration and validation, reasonable performance can be obtained in estimating seasonal and annual rainfall, and mean surface air temperature in Bangladesh. The projected change of rainfall for Bangladesh is about +35% for monsoon season (JJAS), −67% for pre-monsoon (MAM), −12% for post-monsoon (ON) and 107% for winter (DJF) for 2050. On an average, rainfall may be less by more than 50% for all seasons for the year 2060. Similarly, change of mean surface air temperature in different months is projected about 0.5°–2.1°C and 0.9°–3.5°C for the year 2050 and 2060, respectively.