北京雾和霾临界气象条件的气候变化特征

Climate Change Characteristics of Fog and Haze Critical Meteorological Conditions in Beijing

近年来北京市频繁遭受雾和霾天气的影响,表现为天数增多、持续时间增长的特点,这一变化越来越受到专家学者的重视。气象条件是雾和霾污染形成的客观因素。利用北京市观象台多年雾和霾天气(2013-2015年)和气象要素(1961-2015年)观测资料,从气候变化角度出发,研究雾和霾临界气象条件的气候变化特征。研究结果表明:对雾和霾的形成有促进作用的临界气象条件是日平均风速≤1.9 m/s,日相对湿度≥76%,偏南方向的风向;对雾和霾的形成有抑制作用的临界气象条件是日平均风速≥2.6 m/s,日相对湿度≤69%,日降水量≥0.5mm。1961-2015年北京市观象台低风速日数呈增加趋势,且多为西南方向,高风速日数呈减小趋势,污染物清除能力下降,对污染物的累积起关键性作用;相对湿度较高的日数呈减小趋势,相对湿度较低的日数呈增加趋势;日降水量较大的日数呈下降趋势。三种气象条件中相对湿度条件随年代的变化有利于雾和霾的消散,而风速风向和降水量条件随年代的变化不利于雾和霾的扩散和沉降。但有研究表明,在雾和霾污染的形成消散过程中,风速条件起决定性作用,故北京地区较低风速日数的增加是导致大气污染的重要原因。此外,不利的风向条件加重了北京地区污染物的积累聚集。

In recent years,the number of days affected by the fog and haze weather in Beijing significantly increased,and lasted longer. The change have attracted more and more attention of the scientists. Meteorological conditions are the objective factors of fog and haze pollution formation,namely.Based on the fog and haze observation data( 2013-2015) and meteorological observation data( 1961-2015) in Beijing meteorological observatory,this paper studied the climate change characteristics of fog and haze critical meteorological conditions. The results show that the critical meteorological conditions,which promoted the accumulation of fog and haze,are the average daily wind speed≤1. 9 m/s,daily relative humidity≥76%,south wind direction,and which suppressed the accumulation of fog and haze,are the average daily wind speed≥2. 6 m/s,daily relative humidity≤69%,daily precipitation≥0. 5 mm.For the wind speed,the days of low wind speed showed an increasing trend,and more for the southwest,meanwhile the days of high wind speed showed a decreasing trend,which caused the capacity of the pollutants removal decreased and played a key role in the accumulation of pollutants,for the daily relative humidity,the days of high daily relative humidity showed a decreasing trend,and the days of low daily relative humidity showed an increasing trend,for the daily precipitation,the days of high daily precipitation showed a decreasing trend from 1961 to 2015 in Beijing meteorological observatory. The change of relative humidity conditions is conducive to the dissipation of fog and haze,while the change of wind speed,wind direction and precipitation condition is not conducive to the spread and settlement of fog and haze. Some research shows that,wind speed conditions play a more decisive role in the formation and dissipation of fog and haze than others,therefore,the increase of low wind speed days is an important reason for air pollution in Beijing area,and meanwhile the adverse wind direction condition increases the accumulation of pollutants.