The impacts of three PBL schemes on the simulation of boundary layer meteorological factors and air pollutants in Northern China

Abstract

Three planetary boundary layer (PBL) schemes (YSU, MYJ, ACM2) were applied in the WRF-CAMx model to simulate the meteorology variables and air pollutants over Beijing-Tianjin-Hebei region in Northern China in November 2015. The simulated meteorological factors near the surface, and air pollutants were evaluated by observations. All the three PBL schemes overestimated the wind speed in the lower atmosphere and underestimated the 2-m temperature and humidity. The MYJ scheme produced the largest biases on the 10-m wind speed (+1.2 m/s), and the YSU and ACM2 schemes produced similar results. The critical Kv method, which based on the vertical diffusivities, was used to recalculate the model PBL heights. The MYJ scheme gave the lowest PBL heights among the three schemes using the critical Kv method, and then it produced the highest air pollutants concentrations. The YSU and ACM2 schemes produced similar air pollutant concentrations, and the mean concentrations were about 6∼10% less than the MYJ simulations. The stronger surface wind produced by the MYJ scheme decreased the air pollutant concentrations (about 2%).