江苏盐城地区一次持续雾-霾天气过程的综合分析

Analysis of the Sustained Fog-Haze Event in Yancheng

2013年12月上旬江苏盐城地区出现了一次历史罕见的持续重度雾-霾天气,利用盐城市常规气象观测资料、NCEP再分析资料(1°×1°)及环境监测中心站的污染物浓度资料等,对此次过程的环流背景、气象要素、大气层结特征以及动力条件、污染情况等进行了综合性分析。结果发现:12月上旬中高层冷空气势力弱,以纬向环流为主;低层弱的水平风场为雾-霾的发生发展提供了有利的环流背景;稳定的层结特征,近地面高强度的贴地逆温和持续较低的混合层高度是此次雾-霾天气长时间维持的重要因素;边界层内弱正散度及负涡度是此次雾-霾天气得以维持发展的动力因子;通过后向轨迹分型和火点监测资料分析发现:污染物的长距离输送在此次重污染天气的形成过程中起到了一定作用。最后,文中建立了能见度和PM_(2.5)浓度、相对湿度的非线性回归方程,对能见度的预报效果较好,为实际业务应用中雾-霾的预报提供了有利的依据。

A sustained fog-haze event that occurred in early December 2013 in Yancheng was analyzed based on surface meteorological parameters, NCEP reanalysis data （1°×1°）, and air pollutants concentration. The study focus lies in circulation background, surface meteorological elements and atmospheric stratification feature, as well as thermodymamic condition and pollution. The results show that there were weak cold air forces in middle-high level in early December with zonal circulation at 500 hPa. The breezed surface layer was the favorable circulation background for the formation of fog-haze. The maintenance of stable stratification characteristics, high inversion intensity and continuous lower mixed layer were responsi- ble for the sustained fog-haze briefly. In addition, the weak sinking motion, positive divergence and nega- tive vorticity were the dynamic factors for the sustain development of fog-haze. The long-distance trans- port of pollutants played a certain role in the concentration increase of pollutant particulates according to the backward trajectory types and the monitored fire spots. Finally, the non-linear regression formula of visibility, humility and PM2.5 concentration was established, which is better for visibility forecasting and provides a favorable basis for the operation of fog-haze forecasting.