Validation of regional climate model simulation with observational data over Bangladesh

Abstract

A Regional Climate Model (RegCM) developed by ICTP, Triesty, Italy ISemployed for the study of some meteorological parnmeters in and around Bangladesh. Companson between model and observational data has been made at a large spatial domain (over the entire Bangladesh) and a few temporal scales (daily, monthly, and seasonal). It is essential to do some validation of the RegCM model outputs WIththe ground based data say rain-gauge and surface airtemperature to adopt the RegCM for this region. In this connection, the daily raingauge data and surface air temperature of 19 stations throughout the country colle~1edby the BangladeshMetcorological Department (BMD) arc processed to calibrate model output. RegCM is run at 0.54" " 0,54° horizontal grid resolution in two parameterizations: Grell scheme wnh Arakawa-Schubert (GAS) and Fritch-Chappell (GFC) assumptions. GAS run used Lateral BoundaIy Conditions (LBCs) data for 1995-2000 whereas GFC run used LBC data for 1991, 1994, 19% and 1999. A validation study on daily scale rainfall has been conducted over Bangladesh using RegCM model data with conventional rain-gauge observational data for the Pre-monsoon (March- May), Monsoon (June-September) and Post-monsoon (October-November) periods, for the calculation of daily temperature data of the entire year is used. It is found that model overestimates in calculating rainfall in Pre-monsoon and underestimates in Monsoon periods. For the entire rainy seasOn (March-November), model calculates about 101.39% of the surface min for GFC assumption i. e. model overestimated about 1,4 % in rainy-season scale. In GAS assumption, model can simulate the temperature about 94 % in annual scale. Finally, OFC option is better for the calculation of rainfall whereas GAS is better for the calculation of temperature,