| Air quality has received more and more attention from the social scope of various countries around the world,and related work on the interaction between weather conditions and air pollution has also been widely discussed.Previous work was more limited to single-scale weather conditions,ignoring the systematic and comprehensive effects of multi-scale weather conditions on multiple major atmospheric pollutants.This paper uses the T-model oblique rotation principal component method to classify the circulation in the Yangtze River Delta(Xuzhou,Nanjing,Shanghai,Hangzhou),the two lakes region(the areas around Dongting Lake and Poyang Lake),and Beijing(part of the North China area centered on Beijing).The classification was used to explore the relationship between large-scale weather circulation and the current major pollutants,PM2.5 and ozone.The results show that when the study area is under the control of northwest high pressure,northeast high pressure,northern high pressure and weak pressure field type,the PM2.5 concentration is higher;under the control of southeast high pressure,southwest low pressure and eastern low pressure,The ozone concentration easily exceeds the standard.Using the Allwin&Whiteman wind fielld classification method,the wind fields of the four main industrial cities(Xuzhou,Nanjing,Shanghai and Hangzhou)in the Yangtze River Delta were divided into three categories which were ventilation,stagnation and recirculation.Combining large-scale weather circulation and local wind field to explore their impact on air pollution.In most cases,the Yangtze River Delta is mainly affected by stagnation and recirculation local wind fields.From the perspective of regional transmission conditions,it is not conducive to the diffusion of air pollutant particles.PM2.5 was greatly affected by the local wind field.Under the influence of stagnation and recirculation wind field,severe haze events were prone to occur;while ozone pollution was less affected by local diffusion conditions,and has no correlation with local wind fields and humidity.However,it was more sensitive to temperature changes.In the Yangtze River Delta,ozone pollution was more likely to occur when the temperature level was significantly higher than 10°C.Combining a severe haze incident in Shanghai in November 2016(a haze red warning event),an ozone pollution incident in Nanjing in July 2017,and an ozone pollution incident in Xuzhou in March 2019,using the pollutant trajectory numerical model HYSPLIT to explore the trajectory of pollutant particles,further verifying the relationship between circulation patterns,local weather conditions and air quality.During the spread of the COVID-19,strict isolation measures were implemented in the Dongting and Poyang Lake Region and social production activities were greatly restricted.This provided a rare opportunity to compare the impact of weather condition and human activities on air quality in the region.The results of the study showed that the air quality in the Dongting and Poyang Lake Region improved significantly during the COVID-19,and the concentration of PM2.5 decreased sharply,indicating that the reduction of human production and traveling led to lower emissions and reduced PM2.5concentration.The increase in ozone concentration during the COVID-19 was mainly due to the decrease in PM2.5 concentration and the enhancement of atmospheric light transmission conditions,which was conducive to the occurrence of photochemical action and promotes the formation of ozone.The most serious PM2.5 pollution incident under each circulation pattern of Beijing since 2015 was selected for Flexpart-WRF pollutant particle footprint analysis,it was found that under the circulation pattern with a higher average PM2.5 concentration,the particles stay in Beijing for a longer time.For the first time,the climate prediction data was combined with the weather circulation patterns to predict the air quality during the2022 Beijing Winter Olympics.It was found that the circulation pattern of Beijing during the 2022 Winter Olympics would be generally conducive to the diffusion of pollutants and the air quality was predicted to be good.The forecast results could provide decisionmaking basis for formulating emission measures and improving air quality during the Winter Olympics. |
