Assessment of a meteorological mesoscale model's capability to simulate intra-urban thermal variability in a tropical city

Model-based studies investigating the spatial and temporal variability of air temperature are commonly employed to assess heat mitigation strategies in cities. To generate reliable predictions, it is therefore important that models are capable to accurately predict air temperature variability across the city to account for the local climate context. The present study explores the sensitivity of the Weather Research and Forecasting (WRF) model coupled with a multi-layer urban scheme (BEP-BEM) to simulate intra-urban variations of 2-m air temperature during different synoptic conditions in the tropical city-state of Singapore. Two one-month long simulations are conducted during a relatively wet period during the Southwest monsoon and a very dry period during the Northeast monsoon. Model evaluation with micrometeorological data collected at an eddy covariance flux tower shows an overall good performance for turbulence parameters and surface energy balance components, in particular during dry conditions. Difficulties in predicting intermittent cloud cover result in slightly higher errors of modelled 2-m air temperature during the wet period (RMSE < 2.3^∘C) compared to the dry period (RMSE < 1.6^∘C) when using data from nine locations with different urban morphologies. The present research demonstrates the model's capability to predict the intra-urban variability across distinct urban morphologies under distinct weather conditions. However, the model fails to accurately capture the magnitude of the observed nocturnal temperature differences across all weather conditions investigated.