Influence Of The Thermal Effect Of The Qinghai-Tibet Plateau And The East Asian Monsoon On Air Pollution In Typical Regions Of My Country In Winter

In this paper,the National Centers for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR)monthly average reanalysis data from 1954to 2017,haze days observation data from 1954 to 2017 and PM_2.5 daily average mass concentration data from 2013 to 2017 are collected and collated.Firstly,atmospheric apparent heat source on Qinghai-Tibet Plateau is estimated based on thermodynamic equations,and the East Asian winter monsoon index(EAWMI)was calculated.The correlation between the atmospheric apparent heat source(Q₁,called cold source in winter)on the Qinghai-Tibet Plateau and the air quality in China,especially in the five typical regions(Beijing-Tianjin-Hebei,Fen-Wei Plain,Yangtze River Delta,Pearl River Delta and Sichuan-Chongqing regions)is analyzed and studied.Through comprehensive diagnosis and synthesis,the differences of the three-dimensional spatial distribution of the circulation field and temperature field(planes and sections)in China and the typical regions in the strong and weak years of the apparent heat source Q₁ on the Qinghai-Tibet Plateau in winter are compared,and the different distribution characteristics of the climate circulation background causing the strong and weak years of Q₁ on the Qinghai-Tibet Plateau and the influence mechanism on the air quality in different regions in China are discussed.The same analysis is made on the strong and weak years of winter wind to explore the impact of winter wind on pollution in different typical regions of China.Summarizes the primary coverage which this article studies as follows to show:(1)the spatial distribution of correlation between Q₁on the Qinghai-Tibet Plateau and PM_2.5 in December has a northeast-southwest boundary.There is a negative correlation in the southeast region of the boundary,with heavy pollution when the cold source is strong and light pollution when the cold source is weak,while there is a positive correlation in the northwest region of the boundary,with light pollution when the cold source is strong and heavy pollution when the cold source is weak. In the cold source strong year,the northerly winds are stronger in the middle and high latitudes,and there is abnormal northerly downward flow in the southeast region,so the pollution is aggravated by the suppression of convection diffusion in downward flow.However,it exists abnormal updraft in the northwest region, reducing pollution.In the cold source weak year,the situation is just the opposite.(2)the effect of winter monsoon on air quality has a north-south boundary line around 30°N in China.In strong winter monsoon years,the pollution is lighter in the area north of the boundary but heavier in the area south of the boundary,but the situationis opposite in weak monsoon years.Diagnostic analysis of circulation field showedthat in strong winter monsoon years,abnormal downward airflow exists in the area south of the boundary line,which limits the convective diffusion,leading to the increase of pollution.In weak winter monsoon years however,there are ascending airflows,which are favorable for pollutant diffusion.During the strong winter monsoon years,there is abnormal southeast airflow in the lower atmosphere of the Chengdu-Chongqing region and the horizontal wind speed is weak,which is beneficial to localized accumulation of pollutants and aggravates the pollution situation.In the Pearl River Delta region,abnormal westward airflow sinks down, inhibiting local uplift and diffusion and,meanwhile,importing pollutants from the north,thus,the pollution in the Pearl River Delta is aggravated.(3)Con sidering the common influence of the Q₁ on the Qinghai Tibet Plateau and the EAWMI,different typical regions have different conditions for the aggravation of pollution.In Beijing-Tianjin-Hebei region,the pollution is the most serious when the EAWMI is weakens,in Fenwei plain region,the pollution is aggravating when the Q₁ is weak and the EAWMI is abating;in Chengdu-Chongqing region,the pollution is aggravating when the Q₁ is weak and the EAWMI is strong,and in the Pearl River Delta region and the Yangtze River Delta region Therefore,the pollution is more serious in the year of strong Q₁ and strong EAWMI.