影响上海市空气质量的地面天气类型及气象要素分析

地面天气形势及气象要素的变化在空气污染潜势预报中具有很好的指示作用。利用天气学原理将地面天气系统进行分型,探索研究不同地面天气类型对上海空气质量变化的影响。整理、分析2003—2005年地面天气类型和气象要素与空气质量的关系,发现:(1)上海秋冬季以大陆冷性高压系统移动为主,而夏季主要以副热带高压和台风影响为主,春季是冬季与夏季之间的过渡,天气系统转换较为频繁。(2)春、秋、冬季易引起上海市空气污染的天气类型有L型高压、高压、高压前和均压场4种地面天气类型,与空气质量优等级相对应的天气类型是低压槽、高压底和高压后。夏季空气质量优等级对应的天气类型主要有台风、高压(副高)和低压槽。(3)秋冬季节典型天气过程一般经历高压前(或冷空气)→L型高压→高压→高压后(或高压底)→低压槽的转换,PM10浓度变化也表现为先升后降。(4)气象要素的变化也与空气污染存在密切联系,气压与空气污染物的关系为正相关,而气温、相对湿度和风速与空气污染物浓度呈负相关。

THE ANALYSIS OF THE RELATIONSHIP BETWEEN THE AIR QUALITY IN SHANGHAI AND SURFACE PRESSURE PATTERNS AND METEOROLOGICAL FACTORS

The relationship between air quality of Shanghai in 2003-2005 and large-scale meteorological and weather factors is analyzed. The following conclusions have been drawn: (1) Continental high pressure systems mainly occurred in autumn and winter while low pressure troughs mainly occurred in spring, and Shanghai was affected by the subtropical high-pressure belt and typhoons in summer; (2) There are four synoptic systems, namely, a L-shaped high pressure belt, cold air from the eastern area of China, uniform pressure field and high pressure, that can lead to air pollution, while typhoons, the base of high pressures and the back of high pressures are always related to good air quality; (3) In autumn or winter, for one weather process, Shanghai is sequentially located in the front of a high pressure (including cold air), a L-shaped high pressure belt, a high pressure, the back of it and a low pressure trough; at the same time, the concentration of PM10 rises at first and then drops; and (4) Different meteorological elements have different relationships with air pollution: air pressure is positively correlated with air pollutants while air temperature, relative humidity and wind speed are negatively correlated with them.