Influence on the Temperature Estimation by the Planetary Boundary Layer Scheme with Different Minimum Eddy Diffusivity in WRF v3.9.1.1

Abstract

Abstract. The minimum eddy diffusivity (Kzmin) in the planetary boundary layer (PBL) scheme is able to influence the performance of the model in simulating meteorological parameters such as the temperature. However, detailed studies on the sensitivities of the simulated temperature to the settings of Kzmin are still lacking. Thus, in this study, we evaluated the performance of the ACM2 (Asymmetrical Convective Model, version 2) scheme in the WRF (Weather Research and Forecasting) model with different settings of Kzmin, in simulating the spatiotemporal distribution of the temperature in the region of Beijing, China. Five constant values as well as a function were implemented in the model to calculate Kzmin, and the simulation results with different settings of Kzmin were compared and analyzed. The results show that the increase of Kzmin leads to an elevation of the 2-m temperature, especially in the nighttime. We figured out that the deviation of the 2-m temperature at night is mainly caused by the different estimation of the turbulent mixing under stable conditions in simulation scenarios with different Kzmin settings. Moreover, the spatial distribution of the temperature deviation indicates that under various underlying surface categories, the change of Kzmin exerts a different influence on the prediction of the 2-m temperature, and the influence was found stronger during the nighttime than during the daytime, in plain areas than in mountain areas, in urban areas than in non-urban areas. In the nighttime of the urban areas, the influence on the simulated 2-m temperature brought about by the change of Kzmin was found the strongest. In addition, we found that the implementation of a functional type Kzmin in the ACM2 scheme helps to improve the performance of the model in capturing the diurnal change and the vertical distribution of the temperature in this region, compared with that using a constant Kzmin.\n