2014年海口市大气污染物演变特征及典型污染个例分析

主要分析了2014年海口市逐日的空气质量指数(AQI)和6种大气污染物的演变特征,同时,结合卫星遥感和轨迹模式等资料和方法对1次典型污染个例进行诊断.结果表明:海口市2014年的空气质量主要以优和良为主,6 d达到轻度污染级别,1 d达到中度污染(1月5日,AQI值为158).1月污染最为严重,其中,阶段1(1-6日)和阶段3(18-23日)AQI值偏高,阶段2(7-17日)和阶段4(24-31日)偏低.1月东亚地区天气形势演变对海口市AQI值具有动力影响.AQI偏高阶段,地面高压系统位于内蒙古东部,华南低层东北风场有利于污染物向海口市输送;而在AQI偏低阶段,地面高压系统东移出海,低层偏东风场不利于污染物的输送.后向轨迹聚类分析表明,1月海口市比率最大(39%)的气流主要经过大气污染相对严重的广东珠江三角洲(珠三角)地区,有利于污染物的区域传输.污染个例分析表明,海口市污染物浓度变化与气象要素有密切关系,10 m风速较小有助于近地面的污染物在区域内累积,水平风垂直切变偏弱对天气尺度扰动的发展和大气的垂直混合不利.卫星遥感和后向轨迹分析也表明,外源输送与海口市这次大气污染事件有直接关系.

Evolution of ambient air quality and case study of an air pollution event in 2014 over Haikou,China

This study analyzed the Air quality index (AQI) and 6 types of air pollutant sequences in 2014 over Haikou City using diagnostic and statistical methods. A typical pollution event was also diagnosed by applying Satellite Remote Sensing and air parcel back trajectory model HYSPLIT. It is revealed that air quality over Haikou City is "excellent" or "good" most of the days. There are 6 days with slight pollution and 1 day with moderately pollution (5^th January 2014 with the AQI of 158). The worst polluted month is January. AQI value in period-1 (1^st-6^th) and period-3 (18^th-23^rd) is higher than period-2 (7^th-17^th) and period-4 (24^th-31^st). AQI value in Haikou is dynamically consistent with the large-scale synoptic pressure patterns over East Asia. AQI tends to be high when high pressure dominates east Inner-Mongolia with northerly wind in the low level over South China. Cluster analysis of backward trajectories shows that the largest fraction of air flow passed through the Pearl River Delta region with intense pollutant emission, favoring regional transport of pollutants. Analysis of an air pollution event also shows that change of the pollutant concentration is related to meteorological factors, especially 10m-wind speed and vertical wind which are significantly negatively correlated with AQI value. In addition, satellite remote sensing and backward trajectory analyses also show that air polluted event in Haikou City is directly related to external transport.