Influence on the temperature estimation of the planetary boundary layer scheme with different minimum eddy diffusivity in WRF v3.9.1.1

Abstract

The minimum eddy diffusivity (Kzminĝ ) in the planetary boundary layer (PBL) scheme can influence the model performance when simulating meteorological parameters such as temperature. However, detailed studies on the sensitivities of the simulated temperatures to the settings of Kzminĝ 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 Kzminĝ settings when simulating the spatiotemporal distribution of the temperature in the region of Beijing, China. Five constant values and a function were implemented in the model to calculate Kzminĝ , and the simulation results with different Kzminĝ settings were compared and analyzed. The results show that the increase in Kzminĝ leads to an elevation of the 2ĝ€¯m temperature, especially at nighttime. We figured out that the deviation in the 2ĝ€¯m temperature at night is mainly caused by the different estimations of the turbulent mixing under stable conditions in simulation scenarios with different Kzminĝ settings. Moreover, the spatial distribution of the temperature deviation indicates that under various underlying surface categories, the change in Kzminĝ exerts a distinct influence on the prediction of the 2ĝ€¯m temperature. This influence was found to be stronger during the nighttime than during the daytime, in plain areas than in mountain areas, and in urban areas than in non-urban areas. During the night in the urban areas, the influence on the simulated 2ĝ€¯m temperature brought about by the change in Kzminĝ is the strongest. In addition, the model performance using a functional-Type Kzminĝ in the ACM2 scheme for capturing the spatiotemporal distribution of the temperature in this region was also compared with that using a constant Kzminĝ .