Responses of Urban Atmospheric Boundary Layer to Aerosol Radiative Effect over Complex Terrains in Winter
复杂地形城市冬季边界层对气溶胶辐射效应的响应

Focusing on the interaction between the atmospheric boundary layer(ABL) and the radiative effect of urban aerosol,the paper develops and applies the weather research and forecasting(WRF) model,and performs some corresponding numerical simulations and theoretical analyses of Lanzhou area of a complex terrain based on some previous research results.The whole model system integrates the WRF model and the comprehensive ABL model,in which the radiative effect and the diffusion of urban aerosol particles are considered.First of all,using the NNRP2 data in 1989,the meteorological data and air quality data of ABL measurement campaign during December 1989 in Lanzhou,the verification of the model system has been worked out separately for the WRF model and the ABL model,which shows that the two models can run steadily and the performance of the simulated meteorology and concentration fields is preferable.Secondly,by integrating the WRF model and the ABL model with the nesting scheme,the numerical simulation and case analysis of the structures of ABL and characters of air pollutant diffusion under the influence of the radiative effect of atmospheric aerosol are performed.With the comparison of observations and simulated results without the nesting scheme,the simulated results are substantially reasonable and show that the nesting scheme has improved the ABL model's simulated ability.Finally,by employing the established ABL model which is integrated with the WRF model and considering of the diffusion of the aerosol particles and the radiative effect of atmospheric aerosol,the quantitative influence of the aerosol radiative effect on boundary layer structure is discussed.The primary character is that the long wave radiative effect of aerosol leads to an increase of the atmosphere temperature about 0.10.3 K/h near the ground at night.The long wave radiative effect also makes the atmosphere temperature in the lower layer(25300 m) descend about 0.080.15 K/h.The wind speed decreases below 150 m level and the convection is strengthened at the same time.These variations can weaken the stability of boundary layer at night,but this effect can make the wind field(including vertical velocity) and other meteorology fields change at the same time.During daytime,there is an obvious heat increase in the boundary layer due to the aerosol shortwave radiative effect with the increment of about 0.5 K/h.The maximum of the temperature increase occurs near the mixed layer top(500600 m).Influenced by the temperature increase,the vertical wind field and horizontal wind field are adjusted correspondingly,and the wind speed increases by 0.1 m/s below 450 m level and decreases by 0.050.18 m/s above 450 m level.These variations clearly indicate that the differences of temperature increase at different levels induced by the aerosol shortwave radiative effect can weaken the stability of boundary layer to a certain extent,but a series of meteorology fields,including ascending velocity's in