关键词: 重度污染, 颗粒物污染, 环流形势, 气象因素

Abstract:

There was a heavy pollution event from 17th December 2017 to 2nd January 2018 in Chengdu. Based on hourly environmental monitoring data of six stations provided by Ministry of Ecology and Environment of the People’s Republic of China and conventional high level, low level and ground level data provided by MICAPS system, the severe pollution process and the influence of meteorological conditions on this process were analyzed. The results show that during the main period of the process, primary pollutant was PM2.5 and then turned to PM10 at the end of the process. At the incipient stage, Chengdu was located in front of a high-pressure ridge and was controlled by downdraft with increasing AQI. At the enhancing stage, Chengdu was in straight westerlies with weak vertical movement. Pollution strengthened and AQI lasted over 200. At the weakening stage, because of the cold air from the north and south trough moving to the east, the westerlies above Chengdu were strengthened, which helped pollutants to diffuse in vertical direction and made AQI decrease. The concentration of pollutants increased from every nightfall to the next high noon and the air quality got better from afternoon to nightfall. The variation trend of wind speed was contrary to that of the concentrations of pollutants, while the variation trends of the ground relative humidity, the intensity and thickness of inversion layer were in accord with the trend of the concentrations of pollutants. Small cold advection led to short-time decrease of AQI, while continuous cold advection caused by obvious southward-moving cold air and the increase of ground wind speed broke the thermal inversion layer effectively, which led to the obvious decrease of pollutants concentration.

Key words:  severe pollution, aerosol pollution, circulation situation, meteorological condition