风廓线雷达在北京地区一次强沙尘天气分析中的应用

基于北京地区逐小时风廓线雷达数据、大气成分观测数据以及地面常规观测资料对2017年5月3~7日一次沙尘天气过程进行了研究.结果表明：受蒙古气旋影响，全国多地出现空气质量严重污染，其中北京PM₁₀浓度达到严重污染级别时间超过30h.通过对边界层内水平风场、垂直速度以及大气折射率结构常数等要素进行分析，研究发现沙尘爆发前，边界层内出现平均风速达到14.8m/s的西北急流核，该急流核的建立有利于将高层沙尘粒子向近地面传输，而沙尘爆发阶段边界层通风量较前期增加31.6%，中低层的通风量逐渐占据主导地位，使近地面PM₁₀浓度出现爆发性增长.此外，整个沙尘天气过程中，以弱下沉运动为主，垂直速度在1m/s以下，而沙尘天气爆发前，边界层内出现强烈垂直下沉运动，达到5.3m/s.同时，大气折射率结构常数出现1.0×10^-16的高值中心.二者均先于地面污染物浓度的变化，预报时间提前量为8~9h，可为今后沙尘预报提供一定参考.

Application of wind profiler radar in a strong sand dust weather analysis in Beijing

A sand dust period occurred from May 3 to 7 2017 was studied based on wind profiles radar data hourly, atmospheric composition data, and ground surface observation data of Beijing. As the results showed that air quality reached heavy polluted level in many places, in which the concentration of PM₁₀ reached heavy polluted level in Beijing had lasted about more than 30 hours in this sand dust period. The horizontal wind, vertical velocity and the atmospheric refraction index structure constant in boundary layer were analyzed. The main results were given as follow:wind speed of the northwest wind jet core average reached 14.8m/s in the boundary layer, and the establishment of jet core could help dust particles to transfer from upper-level to the ground. It was revealed that the ventilation index in sand dust explosion period increased 31.6% than before, and ventilation index of the middle and low layers played an important role gradually, which leaded concentration of PM₁₀ to increase explosively. In addition, the weak descending motion was the main motion, and the vertical velocity was below 1m/s in this sand dust period, while the vertical velocity could reach 5.3m/s before sand dust explosion period. Meanwhile, atmospheric refraction index structure constant reached the maximum value(1.0×10^-16). Moreover, vertical velocity and atmospheric refraction index structure constant both were earlier than variation of pollutant concentration, and which had a forecast of about 8 to 9 hours in advance, which could play a reference role in forecasting sand dust in the future.