Parameter Optimization of Multi-layer Urban Canopy Model and Simulation of Extreme High Temperature in Beijing−Tianjin−Hebei Urban Agglomeration

Numerical simulation is an effective method to study the urban climate effect, and the parameters are very important for simulation. Using satellite and surface meteorological observations, parameter sensitivity tests of the simulation of extremely high temperatures in the Beijing–Tianjin–Hebei urban agglomeration are conducted, and localized parameter configurations such as surface albedo, surface emissivity, and anthropogenic heat for the model (WRF/BEP/BEM) in the Beijing–Tianjin–Hebei urban agglomeration are determined. It is shown that the locally optimized surface albedo, surface emissivity, and anthropogenic heat have a significant effect on the simulation results of extremely high temperatures in Beijing–Tianjin–Hebei. By localizing these parameters, surface maximum temperature simulation errors are reduced by more than 0.5°C in more than 65% of urban sites. Since 2010, five extreme high-temperature processes have been successfully simulated in the Beijing–Tianjin–Hebei region with the optimized WRF/BEP/BEM. Standard deviations of the extremely high temperature simulated in the model from the observation are about 1.4°C, 0.8°C, 0.9°C, 1.0°C, and 0.7°C, which are decreased by 26.3%, 61.9%, 40.0%, 41.2%, and 36.3%, respectively, compared with the standard deviations of ERA5. After optimization, the model simulation error is obviously reduced, and it can be further applied to the study of the Beijing–Tianjin–Hebei urbanization mechanism under extremely high temperatures.