北京秋冬季空气严重污染的特征及成因分析

The Characteristics and Cause Analysis of Heavy-Air-Pollution in Autumn and Winter in Beijing

近年来北京大气环境质量达标天数明显增加,但是严重污染日依然占近6个百分点,并且没有明显减少的迹象。弄清严重污染,尤其是秋冬季节(9-12月,1-2月)积累型严重污染的时空分布特征和成因,对于污染预警、污染控制具有重要意义。文章首先分析了2000-2005年秋冬季节北京市大气污染达到4-5级的44个案例,发现该类严重污染具有发生时间连续、空间范围广和垂直散布高等特点。运用追踪过程的诊断分析方法剖析了2004年国庆期间和2005年11月初两个典型严重污染过程,说明了气象因子在秋冬季严重污染发生、持续和结束过程中的主导作用。文中最后给出了44个严重污染日气象条件的统计特征:850百帕温度偏高,可高于月均值5-15℃;海平面气压偏低;低空逆温发生概率大于75%;高湿度发生概率大,地面温露差在0-7.5之间约占80%;各层风速都很小,海平面0-2米/秒,850百帕风速2-16米/秒。

In recent years, ambient air quality has been greatly improved in Beijing. Meanwhile, days with heavily polluted air quality still remain about 6% of a year. Therefore, it is crucial to understand the characteristics and causes of heavy air pollution so that we can forecast it, alarm the public and inform the government for emergent emission controlling. In this paper, 44 heavy air pollution cases of autumn and winter were analyzed using the methods of process- diagnosis and mathematic statistics. It was found that heavy air pollution in Beijing was usually a part of the regional level heavy pollution, and meteorological condition was the leading cause that controlled the starts, lasting and ends of a heavy pollution process. The statistical characteristics of some key meteorological parameters are： Temperature at 850hPa 5 - 15℃ higher than monthly average, sea-level pressure low, temperature inversion exists in lower boundary layer, rather high humidity and low wind speed both at sea level and upper level.