Comparison of the Thermal and Dynamic Structural Characteristics in Boundary Layer with Different Boundary Layer Parameterizations

Abstract

AbstractTo evaluate model performance of simulating structural characteristics in boundary layer at the forested areas of northern United States and compare the thermal and dynamic structural characteristics in boundary layer with five different boundary layer parameterizations, high resolution mesoscale WRF model was used in this paper to conduct some experiments with different boundary layer parameterization configurations. The results showed that WRF model with different boundary layer schemes could successfully simulate the characteristics of strong turbulent mixing in boundary layer at daytime and strong inversion, inverse wet and low level jet in stable boundary layer at nighttime except for some individual schemes. Compared with local schemes MYJ and UW, the nonlocal schemes YSU and ACM2 simulated strong turbulent mixing and entrainment at daytime, producing higher temperature, lower humidity, higher mixing layer, larger sensible heat flux in convective boundary layer, which were closer to the results of observations. This indicated that considering the nonlocal transport of large eddy was more reasonable in the instable stratification. But local schemes had some advantages in the prediction of wind speed and direction. TEMF scheme predicted the weakest local turbulent mixing in all schemes, which was difficult to form the mixing layer, and could not describe the characteristics of vertically homogeneous distribution of meteorological elements in convective boundary layer. For nocturnal stable boundary layer simulation, the discrepancies from different schemes were small. But to a certain extent, the scheme YSU overestimated mechanical turbulence at nighttime, leading to strong local turbulent mixing, and could not simulate stable boundary layer well.