Model validation of one-way coupling between WRF and PALM-4U model to evaluate outdoor thermal comfort in tropical region

Abstract

We validate the microclimate model, Parallelized Large Eddy Simulation Model for Urban climate (PALM-4U), against field measurement data. We conduct realistic urban microclimate simulations in a high-density tropical region, specifically in Singapore. The simulation is done using PALM-4U model, coupled with Weather Research and Forecasting (WRF) multilayer urban canopy model (MLUCM). The coupling between WRF mesoscale model and PALM-4U is done via one-way forcing from the WRF simulation output into the initial and boundary conditions of PALM-4U model. Various urban elements are taken into consideration in PALM-4U simulation, including building data, land and surface types, trees as well as the anthropogenic heat generated from buildings, to represent a more accurate and realistic urban setup. It is crucial to validate and calibrate microclimate models using observation data. This helps to ensure that the model‘s predictions are aligned with the actual observed conditions, and to allow for further evaluations, such as for the what-if-scenario comparison. In this paper, we conduct two validation case studies, while one study focuses on the densely built-up area in the downtown (CBD), the other focuses on urban park and vegetation on Bishan-Ang Mo Kio (BAMK) Park. The result suggests that the coupling method can predict well the microclimate in the tropical region both for urban and large vegetated zone within an urbanised area, indicated by the model‘s ability to mimic the diurnal cycle produced by the observation data with relatively low RMSE.