2017年春季华北地区一次典型沙尘重污染天气过程研究

结合空气质量监测站小时监测数据、NECP资料、卫星遥感资料，分析了2017年5月3—5日华北地区一次典型沙尘重污染天气过程.结果表明，此次重污染过程主要由前期的浮尘和后期的扬沙天气造成.前期，蒙古气旋强烈发展将沙尘源地的沙尘抽吸到空中并在偏西风作用下，长距离传输到华北地区沉降，造成大范围浮尘天气，多个城市出现严重污染，PM₁₀浓度增高显著.后期，随着高空横槽转竖并东移，受强冷锋影响，京津等地出现大风扬沙天气，大风过后，空气质量转好，PM₁₀浓度降低至较低水平.起沙源地高空辐散、近地面辐合产生强烈的上升运动将沙尘带到空中并向东传输至华北上空，近地面处于弱辐散场，高空的沙尘缓慢下沉，形成了浮尘天气；高空槽东移，高空辐合，近地面辐散，700 hPa至近地面为强烈下沉运动，是形成此次扬沙天气的主要原因.结合天气形势分析和特征量诊断，给出了华北地区此次浮尘和扬沙天气的天气学概念模型.

Study on a typical dust pollution process in North China in spring in 2017

Based on the hourly monitoring data from the national air quality monitoring station, the weather data and the weather diagnosis data from the NCEP, the remote sensing data from the satellite, this study analyzed a typical dust heavy pollution in North China from May 3 to May 5 in 2017. The results showed that:The heavily-polluted event was mainly related to the floating dust as well as the blowing sand. In the early period, the Mongolian cyclone strongly dominated in the North China, sucking dust up into the air. Under the westerly wind weather condition, the dust was transported to the North China, leading to floating dust pollutions in the large-scale areas, with the PM₁₀ concentrations increasing significantly. In the later period, the high-altitude horizontal slot turned vertical and moved eastward, and the gale weather occurred in Beijing and Tianjin. After the cold front, the air quality was getting better with PM₁₀ concentrations decreasing to a low level. High altitude divergence combined with the surface intense convergence produced a strong ascending airflow in the source of sand, which brought the dust up to the air. The high-altitude dust slowly sinks in the weak surface divergence field. The moving eastward trough, converging at high altitude, divergence near the ground, strong sinking airflow from 700 hPa were the primary causes for the formation of this sand blasting. Based on the weather situation analysis and the diagnosis information of weather, the conceptual models of floating dust and blowing sand weather in North China are given.