风廓线雷达资料在北京秋季雾霾天气过程分析中的应用

Application of Wind Profile Radar in Analyzing Autumn Fog and Haze Process in Beijing

利用L波段风廓线雷达资料,对北京2014年10月7-10日持续性雾霾天气过程的机理进行了研究,结果表明:低空偏南气流对雾霾的维持和发展有明显影响,当偏南风速大于8m/s时对大气扩散能力有一定改善作用,会抑制PM2.5浓度的持续增加;中低空弱冷空气扰动的下传高度决定了对污染物浓度的影响,当扰动不能到达近地层时,对污染物浓度影响较为微弱;雾霾维持阶段,近地层信噪比强度一般为10~35dB,可反映雾霾层的厚度;折射率结构常数可用于判断大气边界层高度变化情况,在热力湍流和污染物粒子散射作用下,白天边界层折射率结构常数可比夜间增大约3个量级。

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 PM2.5 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.