基于异常天气分析法探究四川盆地冬季大气污染的气象成因

Exploring the Meteorological Causes of Atmospheric Pollution in Winter in Sichuan Basin Based on Abnormal Weather Analysis Method

以四川盆地冬季大气污染的气象成因为主要研究对象,采用异常天气分析方法,利用2014年3月-2019年2月四川盆地环境与气象观测站点的监测资料,探究2014-2018年冬季四川盆地细颗粒物(PM2.5)浓度的时空分布特征,并结合对气候平均状态下大气环境形势的分析,研究大尺度大气环流异常与四川盆地冬季PM2.5污染之间的响应关系。结果表明:2014-2018年冬季四川盆地PM2.5中度以上污染的天数呈波动式下降特征,高浓度的PM2.5污染主要集中在盆地西南部及东北部城市群;2014年和2016年冬季四川盆地上空500 hPa暖高压偏暖偏强,近地面附近存在"距平逆温",低空盛行偏南风,天气形势静稳,大气污染物不易扩散,促发PM2.5重污染的形成;近五年四川盆地冬季大气空气质量较好时主要对应两种大气环流形势,一种为500 hPa高空受冷低压的影响,盆地上空冷空气活跃,对流增强易产生降水,另一种为受500 hPa冷高压的控制,700 hPa高空盛行北风带来干冷空气南下,这两种环流形势均有利于大气污染物的扩散和清除。

This paper analyzes the meteorological causes of atmospheric pollution in winter in Sichuan Basin.By the abnormal weather analysis method,and using the monitoring data from routine environmental and meteorological data from March 2014 to February 2019,combined with the analysis of atmospheric circulation patterns under climatological mean condition,the paper researches the response relation between large-scale atmospheric circulation anomaly and PM2.5 pollution in winter in Sichuan Basin.The main conclusions are as follows:the concentration of PM2.5 and the number of days above moderate pollution in 2014-2018 in Sichuan Basin show a fluctuating decline in winter in recent five years.The high concentration of PM2.5 accumulates in the southwestern and northeastern urban agglomerations of the basin.In the winter of 2014 and 2016,the 500 hPa high-pressure system over the basin is stronger and warmer,and there is "offset inversion" near the ground,the southerly wind is prevailing in the low altitude,the weather situation is static and stable,and the atmospheric pollutants are not easy to spread,which leads to the formation of heavy pollution.There are two main patterns of the circulation situations during the periods of good air quality over Sichuan Basin in winter.One is that under the influence of the cold low-pressure system in 500 hPa,the cold air is active in Sichuan Basin,enhancing the convection to produce precipitation;and the other one is that under the cold high-pressure system control in 500 hPa upper air of Sichuan Basin,the prevailing north wind in 700 hPa upper air brings the dry and cold air to the Sichuan Basin.Both of these circulation situations are favorable to the diffusion and eliminating pollutants.