稳定天气形势下京津冀和长三角地区重度污染过程气象成因解析

基于空气质量数据、天气图、常规地面气象观测数据、秒探空资料以及高分辨率的降水数据,剖析了2015年12月19—27日发生在我国东部地区的一次大范围重度污染过程的特征及成因.结果表明,此次污染过程中,我国东部地区主要受到东路冷高压、均压场以及西路冷高压的影响,在东路冷空气及均压场的影响下,BTH（Beijing-Tianjin-Hebei）地区污染物不断累积,西路冷空气影响下污染物浓度开始降低,YRD（Yangtze River Delta）地区在稳定的均压场下污染物不断累积.污染期间,BTH及YRD近地层均有逆温现象发生,且逆温层越厚、强度越大,污染越重.此外,较低的近地面风速、较高的相对湿度,亦不利于污染物的扩散稀释,导致此次重度污染事件的发生和持续.YRD地区在重度污染发生时,有降水现象发生,导致YRD地区PM_2.5浓度呈现波动性变化.

The meteorological causes of a heavy pollution process in BTH and YRD area with stable weather condition

Using air quality data, weather maps, surface meteorological observation data, 1-Hz sounding data, and high-resolution precipitation data, the characteristics and causes of a large-scale heavy pollution process in eastern China from Dec. 19 to 27, 2015 are analyzed. The results show that during this pollution process, the eastern China was influenced by the eastern cold high pressure, the uniform pressure and the western cold high pressure. When impacted by the eastern cold air and the uniform pressure, the pollutants in BTH (Beijing-Tianjin-Hebei) accumulated, while under the influence of western cold air, they decreased. In YRD (Yangtze River Delta) area, the pollutants accumulated due to the uniform pressure. During this pollution process, inversions occurred near the surface in both BTH and YRD area. The thicker the inversion layer was, the greater the intensity and the heavier the pollution would be. In addition, the low surface wind speed and high relative humidity were also detrimental to the diffusion and dilution of pollutants, leading to the occurrence and persistence of this severe pollution event. Moreover, the PM_2.5 concentration was found to be fluctuating in YRD area because of the precipitation.