Study On The Influence Of Asian Summer Monsoon On Summer Ozone Concentration In Chin

With rapid economic development,the 14th Five-Year Plan has unveiled a new journey to build socialism in an all-round way,while air pollution in large urban agglomerations is also increasingly aggravated,which cannot be ignored.Frequent ozone pollution in summer does great damage to atmospheric visibility,ecosystems and human health.Long-term exposure to ozone pollution will cause a series of acute and chronic diseases.Based on surface observational data of ozone（O₃）,reanalysis data,the Goddard Earth Observing System Chemical Transport Model（GEOS-Chem）and multi-model intercomparison results of The Coupled Model Intercomparison Project 6（CMIP6）,this study is committed to exploring the impacts of atmospheric circulation patterns and Asian summer monsoon,on ozone pollution in China,to provide reference information for decision-making of air pollution prevention and control policies.This study can provide reference for achieving the balance between economic development and environmental protection.Ozone pollution is greatly affected by regional atmospheric circulation.Based on the surface observational data of O₃,this study identified the months with severe ozone pollution in North China Plain（NCP）,the Yangtze River Delta（YRD）,Sichuan Basin（SCB）and the Pearl River Delta（PRD）.It is found that the atmospheric circulation pattern and meteorological variation of ozone pollution in NCP and YRD are consistent,showing high temperature and low humidity,which are conducive to the chemical reaction of O₃.Abnormal high pressure and the weakening of prevailing southerly winds lead to the poor diffusion conditions,easy accumulation of O₃ pollutants and increased concentration.Local accumulation is the main cause of ozone pollution in the NCP and YRD.Different from the NCP and YRD,the ozone pollution in SCB and PRD is due to a decrease in warm,moist and clean air from the ocean.At the same time,abnormal northerly winds transport O₃ concentration from the heavily polluted northern part to SCB and PRD,resulting in O₃ pollution.In addition,the monsoon climate in China is significant,and the Asian summer monsoon has an important impact on the production and transmission of O₃ and its precursors in summer over China.This work explores the effect of interannual variations of the Asian Summer Monsoon（ASM）,including East Asian Summer Monsoon（EASM）and South Asian Summer Monsoon（SASM）on the O₃ concentration in summer in China.The results indicate that there is a significant positive correlation between EASM intensity and surface O₃ concentration in central and southern China（97.5°-117.5°E,20°-35°N）,with a correlation coefficient of 0.6.Compared with weak EASM years,O₃ concentrations increased by 5 ppb（10%）in strong EASM years due to the decrease in prevailing southwesterly winds led to the weakening of O₃transboundary transmission.SASM can be divided into two parts.The relationship between SEASM（Southeast Asian Summer Monsoon）near East Asia and O₃ concentration in southern China（100°-117.5°E,22°-32°N）is similar to EASM,showing a significant positive correlation.In contrast,SWASM（Southwest Asian Summer Monsoon）is negatively correlated with surface O₃ concentration in eastern China（110°-117.5°E,22°-34°N）,with the largest difference in O₃concentration between the strong and weak monsoon years exceeding 5 ppb（10%）.This may be due to the appearance of abnormal southerly winds that blow pollutants away from the northern boundary of eastern China,causing differences in O₃ concentrations.ASM has an important impact on O₃ concentration in China,regulating O₃ concentration by altering transboundary transmission associated with large-scale circulation variations.Future projections of ASM suggest that sustainable development and moderate development scenarios are ideal pathways to help mitigate O₃ pollution,while high social vulnerability and radiative forcing scenarios may exacerbate future O₃ pollution in China.