Potential effect of urbanization on extreme heat events in Metro Manila Philippines using WRF-UCM

Abstract

This study aims to assess the performance of Weather Research and Forecasting coupled with the urban canopy model and anthropogenic heat (AH) on extreme heat events and determine the potential effect of urbanization on these extreme heat events in Metro Manila. Simulations with well-represented urban land use capture temperature (Mean Bias is -0.39 °C), especially during nighttime compared to simulations without urban land cover. The simulations with urban areas at night show an increase in sensible (∼75 W m−2) and ground heat fluxes (∼125 W m−2), while a decrease in latent heat flux (∼13 W m−2) compared to simulations without urban areas. Simulations with urban cover have temperatures more than 4 °C in central Metro Manila than simulations with no urban grids. Sensitivity tests with three different planetary boundary layer (PBL) and radiation schemes show that ACM2 performed best, while RRTMG captured distribution. During the heatwaves, the daytime and nocturnal urban heat island intensities (UHIIs) are estimated at 0.75 °C and 2.17 °C, respectively. The AH effect on UHII is more substantial during nighttime and contributes about 10 % to the UHII compared to the urbanization effect. This study may help policymakers identify hotspots in Metro Manila and develop adaptation/mitigation strategies for extreme heat events.