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Lband wind profile radar data is used to analyze the mechanisms of persistent fog and haze process in Beijing from 7 to 10 October 2014The results show that the lowlevel southerly wind has a significant influence on the maintenance and development of fog and haze. The southerlies with velocity greater than 8 m/s can improve atmospheric diffusion, and inhibit the increase of PM25 concentration. The altitude to which midlow level weak cold turbulence can reach determines its impact on pollutant concentration. When the turbulence cannot reach the surface layer, the impact on pollutant concentration is rather weak. During the maintenance of fog and haze, the intensity of surface SNR (Signal Noise Rate) is usually 10 to 35 dB, which can reflect the thickness of the fog and haze layer to a certain extent. The structural parameter of turbulence reflectivity can be used to describe the diurnal variation of the atmospheric boundary layer, which can increase by about 3 orders of magnitude in daytime than nighttime due to the thermal turbulence and scattering effect of pollutant particles.