贵阳市两次空气污染过程的气象条件分析

Analysis of Meteorological Conditions of Two Air Pollution Processes in Guiyang

利用环境空气质量指数(AQI)、降水量及大气环流场资料对2013年贵阳市2次空气污染过程进行分析,从天气形势和空气污染演变角度分析气象因子在其中的作用。结果表明,2次污染过程中动力和热力气象因子均为其维持和发展提供有利条件,但存在异同。相同之处在于:2次污染过程中贵阳市均处在地面静止锋后,地面风速较小,不利于近地面空气污染物向区域外的水平输送;2次污染过程中贵阳上空均处在高空脊前的异常下沉气流区,配合对流层中低层的异常水平风速垂直梯度减小,均利于减小大气的斜压性、减弱天气尺度扰动的发展,同时异常逆温层的存在使大气近地层更加稳定,均不利于空气污染物的垂直混合、向高空扩散,加强了污染物在近地面集聚。不同之处在于:2次污染期间贵阳市上空分别存在不同程度的低层单层逆温和中、低层双层逆温,逆温增强时段与污染最重时段相对应,逆温层的存在大大增强了大气层结稳定度,为污染过程的维持和发展提供有利的气象条件;2次污染过程中风场的三维特征对演变过程中逆温层的影响各异,第1次过程中对流层中层偏南风利于将南方的暖湿气流输送到贵阳市上空,利于逆温层的增温、增湿和发展、维持,而第2次过程中高、低空一致的偏北风,在近地层易形成冷垫、抬升暖空气,加强逆温层的维持和发展。

The paper compared and analyzed the effect of meteorological conditions from the aspect of atmospheric circulation background and pollution evolution of two air pollution processes in Guiyang based on the Air Quality Index(AQI), precipitation and atmospheric circulation field. The results show that both dynamic and thermal meteorological factors provided favorable conditions for maintenance and development of the two pollution processes. However, there were similarities and differences. The similarities were that Guiyang was located behind the ground stationary front in the two pollution processes where the surface wind speed was small, which wasn’t in favor of the horizontal conveying of air pollutants near the surface. Guiyang was located in the anomalous downdraft region in front of the high ridge, with the decrease of the anomalous vertical wind shear in the middle and lower troposphere, the atmospheric baroclinicity reduced and the synoptic scale disturbance weakend. The presence of anomalous inversion layer made the atmospheric stratification more stable near the surface layer. All of the above were not conducive to the vertical mixing and the high-altitude diffusion and enhanced the accumulation of pollutants near the ground. The differences were that there were different degrees of single and double inversion layers over Guiyang during the two pollution processes. The inversion enhancement period corresponded to the most polluted period. The inversion layer greatly enhanced the stability of atmospheric stratification and provided favorable meteorological conditions for the maintenance and development of the pollution processes. The wind field had different effects on the inversion layer during the two pollution processes. In the first pollution process, the southerly wind in the middle troposphere was beneficial to transporting warm and moist airflow from the south, which was conductive to the development of warming and humidifying of the inversion layer over Guiyang city. In the second pollution process, the northerly wind at high and low troposphere was easily to form cold air cushion and raise the warm air, so as to strengthen the maintenance and development of the inversion layers.