Research On The Influence Of Different Boundary Layer Schemes Of WRF-Chem On The Simulation Of Pollutant Concentration In Nanjing Area

This study is based on WRF-Chem（weather research and forecasting chemistry model）air quality model,using YSU（Yonsei University）,MYJ（Mellor Yamada janjic）,MYNN2（Mellor Yamada Nakanishi Nino Level 2）,ACM2（asymmetric reactive）Four boundary layer schemes,ACM2R2（the turbulence diffusion coefficient threshold of the lowest 6 layers of the model is changed to 2m2s-1）and ACM2R5（the turbulence diffusion coefficient threshold of the lowest 10 layers of the model is changed to 5m2s-1）,are used to simulate a weather pollution process in Nanjing in winter,and the influence of different boundary layer schemes on the simulation of pollutant concentration in Nanjing is analyzed.The main research results are as follows（1）The simulation results of surface meteorological elements and wind temperature and humidity profiles of six schemes show reasonable diurnal variation characteristics and height variation trend,and the differences of meteorological elements among different boundary layer schemes are small.At the same time,the daily variation of boundary layer height and its characteristics are well simulated.（2）Different boundary layer schemes have different advantages in simulating different pollutant concentrations.MYNN2 scheme is better in simulating O₃concentration;MYJ scheme is better in simulating PM₁₀ concentration,YSU scheme is better in simulating SO₂ concentration;ACM2R2 scheme is better in simulating CO,NO₂ and PM_2.5 concentration.（3）From the deviation of the whole period,ACM2R2 is the closest to the observed values in terms of simulated CO,NO₂ and PM_2.5 concentrations.This is due to the higher turbulent diffusion coefficient of ACM2R2 at night,which is more conducive to the upward diffusion of pollutants from the surface,so that the surface pollutant concentration of ACM2R2 scheme at night is lower than that of the original ACM2 scheme,which improves the overestimation of the original scheme.The turbulent diffusion coefficient of ACM2R5 is higher at night,and the diffusion is too strong in the later stage,resulting in a large underestimation.When there is underestimation in the original scheme,ACM2R5 scheme will deviate more than the observed value（4）The difference of turbulent diffusion coefficient is an important reason for the difference of pollutant concentration simulation.It is necessary to accurately parameterize the turbulent diffusion coefficient of the boundary layer scheme at night to improve the accuracy of pollutant concentration simulation.