Assessment of precis regional climatic model for some selected climatic parameters in Bangladesh

Abstract

Bangladesh is considered as one of the most vulnerable zone under climate change where climate change is likely to exacerbate frequently occurring climatic hazards such as flood, cyclone, storm surge, drought and heavy rain. Long term planning is impossible without any idea of change of climate to be anticipated in the future. Rainfall and temperature are the most important climatic parameters and regional climate models are the main tools available for developing projections of climate change. The assessment of PRECIS regional climate model in Bangladesh is performed with the surface observational data of rainfall and temperature collected by the Bangladesh Meteorological Department at 7 observational sites throughout the country from 1990-2010. PRECIS is overestimating the rainfall at different regions of the country except at a few locations where it is underestimating. Data averages from all seven regions over Bangladesh with yearly variation provide reasonable validation of PRECIS in Bangladesh than regional variation. Monthly biases are calculated +1.15 mm/day in May and – 1.55 mm/day in September respectively. Regional PRECIS data underestimates temperature at different regions of the country as compared to BMD data except for some regions where it is overestimating. PRECIS annual average of maximum and minimum temperature values vary by 0.4 to 2.7 ºC and 0.1 to 0.5 ºC respectively from BMD values. Thus this work revealed satisfactory results for validation of PRECIS in Bangladesh. In the next step PRECIS model generated rainfall and temperature scenarios are calibrated with ground-based observed data during 1990-2010 in Bangladesh. Through calibration, regression coefficients such as slopes and constants are obtained at seven regions over Bangladesh. The regression coefficients are utilized in obtaining the projected rainfall and temperature for Bangladesh in 2015, 2025, 2035, 2045 and 2050. The future daily average rainfall for Bangladesh is found to increase about 1.7 to 5.8 mm/day from the past in July to August which are the month of monsoon season but falls slightly about 0.2 to 0.7 mm/day at winter and pre-monsoon periods. The maximum and minimum temperature will be increased in future years. Annual average of maximum and minimum temperature values are increasing between 1.70 ºC and 2.0 ºC. This work decisively disclosed that PRECIS may be admissible in future impact studies of climate change in Bangladesh.