Simulation of the influence of a fine-scale urban underlying surface on the urban heat island effect in Beijing

Abstract

In this study, the weather research and forecasting (WRF) model coupled with slab model and single-layer urban canopy model (SLUCM) was used to simulate the urban heat island effect in Beijing. The effects of the refined local climate zone (LCZ) urban underlying surface and Moderate resolution Imaging Spectroradiometer (MODIS) land use data on temperature simulated results were compared through sensitivity tests. These two types of underlying surface data present similar simulation error tendencies, showing an overestimation of the 2 m temperature at night. The simulated temperature results using MODIS land use data are closer to the observations than those simulated using the LCZ data. However, the MODIS land use data provide one classification for urban surface, which cannot reflect the complex urban morphology, whereas the LCZ concept divides urban land surface into ten categories that can reflect the surface characteristics more accurately. The sensitivity of different urban canopy parameters on temperature simulation provides priority parameters for model improvement. Real data were used to improve the parameter table setting in the urban canopy model and thus enhance the simulation ability of the LCZ test. The urban fraction, emissivity, and albedo in the parameter table were calculated and replaced. It was found that the use of the accurate emissivity provided the best simulation results. There are negative correlations between near-surface temperature and emissivity/albedo, and a positive correlation between near-surface temperature and urban fraction. The influence of the parameters on the simulated temperature at night was more evident than that during the daytime.