The Haze Pollution In The Context Of Climate Change Over Guangdong Province:Variation Characteristics And Influencing Factors

Due to the development of global economics,China is undergoing a dramatic urbanization process.Especially,for Guangdong province,"the reform and opening-up policy" and forceful economic reform started off before other areas.Over the past several decades,unprecedented expansion of industrialization and urbanization caused the dramatical increase of atmospheric pollutants.We analyze the variation characteristics and influencing factors of haze pollution over Guangdong region during 1973-2018.In addition,we present an analysis of the corresponding relationships among the joint effect of El Ni?o-Southern Oscillation(ENSO)and Indian Ocean Dipole(IOD)and haze pollution over Guangdong.The main contents and results are described below:(1)A significant descending trend of visibility are observed during the period of 1973-2007.Since 2007,the visibility experiences an increasing trend,respectively.On a seasonal basis,the highest visibility over Guangdong occurred in summer,followed by autumn,spring,and lowest in winter,which is consistent with the seasonal characteristics of atmospheric stability.The average relative humidity of winter is higher in haze days than that in clean days.The wind speed of winter is larger in clean days than that in haze days.(2)The change of air pollutant emission cannot entirely explain the variation of haze pollution in Guangdong.The meteorological and climate contribution to PM2.5 concentration is at least 14%.Analysis of the relationship between climatic parameters and pollution indexes emphasizes that the global temperature and emission affect the long-term trend of winter haze days.ENSO and IOD play a significant role in interannual time scale.(3)Persistent low values of PM2.5 are found to prevail during the years when concurrent IOD positive phase(pIOD)and El Ni?o occur.Only when ENSO and IOD are in-phase combinations,the robust ascending and precipitation anomalies are found,which contributes to mitigate haze pollution by aerosol wet scavenging over Guangdong.(4)Based on CART algorithm and decision tree regression model,we identify the climate factors that affected the PM2.5 concentration over Guangdong from 1979 to 2015 in winter.We confirmed that the PM2.5 concentration in Guangdong is jointly affected by emission,East Pacific/North Pacific Oscillation,ENSO,North Atlantic Oscillation,East Atlantic,East Atlantic-west Russia,Western Pacific,Arctic sea ice,IOD and Pacific Decadal Oscillation.The model performance from good to bad is:CART decision tree regression>Random Forest>Multiple linear regression.