Numerical simulation of seasonal mesoscale atmospheric flow-field variables using ARW over the Singapore region: impact of land use land cover

In the present study, the effect of land use land cover information on the simulation of seasonal planetary boundary layer (PBL) flow-field variables over the Singapore region is analysed using the Advanced Research Weather Research and Forecasting (ARW) mesoscale model. The results achieved are compared using the standard ARW Moderate Resolution Imaging Spectroradiometer (ARW-MODIS) global land cover data and a regional land cover map produced at the Centre for Remote Imaging, Sensing and Processing (ARW-CRISP), Singapore. The high-resolution simulations are conducted with triple-nested domains (horizontal grid spacing 27, 9 and 3 km) and 51 unequally spaced vertical sigma levels. The evolution of PBL variables and rainfall are modelled for four seasons (northeast monsoon season, first inter-monsoon period, southwest monsoon season and second inter-monsoon period). For the purpose of numerical simulations, 30 days in each season were considered and the model-simulated variables were validated with in situ available meteorological observations and rainfall at four stations over Singapore. The simulation results highlight the broad variation of the low-level flow-field in different seasons. The ARW mesoscale model simulated diurnal trends in surface meteorological variables and rainfall are in better agreement with observations by using the ARW-CRISP regional land cover map compared to ARW-MODIS global land cover data. Stronger winds are found during monsoon seasons compared with inter-monsoon periods. Overall, the results of the present study indicate that regional level air quality monitoring and prediction capabilities around Singapore can be improved by using up-to-date land cover products designed to take into account regional land cover characteristics.