一次强沙尘暴活动对中国城市空气质量的影响

Influence of a Severe Dust Storm on Chinese Cities' Air Quality

对2006年4月8—12日发生在中国北方地区的一次强沙尘暴天气过程及其对中国大陆城市空气质量的影响进行了分析研究。结果表明:①造成此次沙尘天气过程的直接原因是伴随着西伯利亚强冷空气南下的冷锋自西北向东南方向的移动。沙尘暴鼎盛时期卫星观测的中国境内大气沙尘气溶胶指数(AI)的分布存在一个高值区和两个次高值区。高值区位于内蒙古西部地区、河西走廊和河套地区;两个次高值区分别位于塔克拉玛干沙漠及华北至东北地区。与此同时,地面观测的最小能见度小于10km的气象站点分布最密集的地区也主要分布在上述3个区域。AI的分布与最小能见度的分布之间有着很好的一致性。②这次沙尘天气过程的影响范围主要在33°N以北。从西到东沙尘天气影响的程度逐渐减轻,受污染最严重的城市集中在西北地区东部。根据锋面过境时间与发生大气污染事件时间的对比可将受沙尘天气影响的城市大致分为两类:第一类城市大气污染事件发生在冷锋过境期间(Ⅰ类城市),第二类城市大气污染事件发生在冷锋过境前(Ⅱ类城市)。Ⅰ类城市受沙尘过程影响发生空气污染事件的持续时间相对较短,空气污染事件主要出现在锋面过境前后。Ⅱ类城市受沙尘过程影响发生空气污染事件的持续时间相对较长,空气污染事件的出现时间要明显超前于锋面过境时间。两类城市的共同特征是能见度与空气污染指数(API)之间存在着良好的反位相关系。

During April 8^th to 12^th, 2006, a severe dust storm occurred in northern China. The climatic background of drought, synoptic situation and the impact of this dust storm on Chinese cities＇ air quality are documented in the current study. The main results can be summarized as follows： ①The distribution of satellite-observed aerosol index （AI） shows a high value region and two sub-high value regions in northern China. The former lies in western part of Inner Mongolia, Hexi Corridor and Hetao area, and the latter two lie in Taklimakan desert, North China to Northeast China. The meteorological observation stations with minimal visibility lower than 10 km mainly distribute in the three above-mentioned regions. The spatial patterns of AI and the minimal visibility are similar. ②The impact area of this dust weather was mainly located on north of 33°N. Moreover, the influence of the dust storm weakened gradually from west to east and the cities influenced most severely by the dust storm concentrated on the eastern part of Northwest China. Based on the lead-lag relationship between the arrival of cold front and the occurrence of air pollution, the cities which suffered from the dust storm can be divided into two kinds. In the first kind of cities, the air pollution event concurred with the arrival of cold front; and in the second kind of cities, the air pollution event occurred before the arrival of cold front, with a lasting time relatively longer than that in the first kind of cities.