基于风廓线雷达对成都地区典型持续性重污染天气的研究

基于风廓线雷达数据、大气污染数据及气象数据对2017年12月17日—2018年1月3日成都地区的一次持续性重污染天气过程进行研究,并对两次污染物浓度爆发式增长阶段的污染原因及污染物来源进行了分析.结果表明:①在这次重污染天气过程中,风廓线雷达高精度的风场资料(包括水平风速、风向、垂直风速、大气折射率结构常数C■)配合其他气象要素在分析两个污染阶段污染物的累积及扩散、输送中可以发挥重要的作用,即当成都地区水平风场风速较小且风向多变时,此时受静稳型天气控制,污染物浓度会快速累积增长,而当出现较强的东北风时,可能会有沙尘污染物的输入,应注意沙尘天气的提前预警.垂直风场中垂直速度和大气折射率结构常数C■的变化往往影响着污染物浓度的变化,由于风廓线雷达具有较高的时间分辨率,因此,对污染天气过程的变化有一定的指示意义.②结合局地环流指数和边界层通风量,重新定义了一种适合成都地区风场特征的通风指数:有效通风量(EVI),从而表明第一阶段污染的主要原因是成都地区由静稳型天气控制,边界层内风场对污染物的稀释扩散能力差,导致污染物累积.③通过后向轨迹模拟并结合PM_(2.5)浓度数据进行聚类分析,认为第二阶段污染主要是东北方向携带有大量沙尘污染物的气团输送到成都地区导致的,与源于西北地区沙尘天气的沙尘输送密切相关.

Study on typical continuous heavily polluted weather in Chengdu area based on wind profiler radar

Using wind profiler radar data, air pollution data and meteorological data, this study analyzed weather processes responsible for two persistent heavy polluted periods in Chengdu area from December 17, 2017 to January 3, 2018. Two explosive growth periods of pollutant concentration were found during this period of time. The characteristics of the wind field were significantly different in these two heavy-polluted periods, suggesting different sources of pollutants and accumulation reasons. From effective ventilation index (EVI), which was redefined by combining local circulation index and boundary layer ventilation, the first heavy polluted period was due to stationary weather over the Chengdu area. Stationary weather resulted in poor dilution and diffusion of pollutants in the boundary layer and thus the accumulation of pollutants. For the 2^nd heavy-polluted period, the backward trajectory simulation and cluster analysis of PM_2.5 concentration data revealed that transport of air masses from Northwest carrying large amount of dust pollutants to Chengdu should be the primary reason. This study proves that high-precision wind profiler radar data, particularly horizontal and vertical wind speed, wind direction, atmospheric refractive index structure constant integrated with other meteorological factors, are extremely helpful to understand the sources and reasons for pollutant accumulation, diffusion and transportation.