Abstract
Regional climate model is a scientific tool to monitor present climate change and to provide reliable estimation of future climate projection. In this study, the Regional Climate Model version 4.7 (RegCM4.7) developed by International Centre for Theoretical Physics (ICTP) has been adopted to simulate rainfall scenario of Bangladesh. The study examines model performance of rainfall simulation through the period of 1991-2018 with ERA-Interim75 data of 75 km horizontal resolution as lateral boundaries, downscaled at 25km resolution using the mixed convective precipitation scheme; MIT-Emanuel scheme over land and Grell scheme with Fritsch-Chappell closure over ocean. The simulated rainfall has been compared both at spatial and temporal scales (monthly, seasonal and annual) with observed data collected from Bangladesh Meteorological Department (BMD) and Climate Research Unit (CRU). Simulated annual rainfall showed that the model overestimated in most of the years. Overestimation has been observed in the monsoon and underestimation in pre-monsoon and post-monsoon seasons. Spatial distribution of simulated rainfall depicts overestimation in the southeast coastal region and underestimation in the northwest and northeast border regions of Bangladesh. Better estimation of rainfall has been found in the central and eastern parts of the country. The simulated annual rainfall has been validated through the Linear Scaling bias correction method for the years of 2016, 2017, and 2018 considering the rainfall of 1991-2015 as reference. The bias correction with linear scaling method gives fairly satisfactory results and it can be considered in the future projection of rainfall over Bangladesh.
Highlights
Climate change is one of the greatest threats that is facing our world today in the 21st century
The primary objective defined in this study is to examine the model performance by analyzing simulated monthly, seasonal and annual rainfall over Bangladesh
The present study attempts to verify the downscaled rainfall for Bangladesh simulated through RegCM4.7 driven by EIN75 boundary forcings
Summary
Climate change is one of the greatest threats that is facing our world today in the 21st century. Several climatic models which are known as Global Climate Model or Global Circulation Model (GCM) have been developed to simulate and predict climate parameters over the decades These models are based on complex mathematical relationships between the major climate system components like atmosphere, land surface, ocean, and sea ice. GCM is developed based on global patterns in the atmosphere and ocean. Though the coupled Atmospheric-Ocean Global Circulation Model (AOGCM) predicts the future changes of climatic parameters, but are not able to resolve regional features such as topography, land use patterns, and cloud features due to coarse horizontal resolution (Almazrouri, 2012; Sigdel and Ma, 2016). In the dynamic downscaling process, information about climate change at a higher resolution for a particular region can be derived using RCM by employing GCM data or Reanalysis data as lateral boundary conditions
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