Analysis And Simulation Of The Impact Of Arctic Oscillation On Haze Pollution In China

Aiming at improving the impact uncertainties of abnormal climate on haze pollution in China,this study firstlyanalyzed the uncertainties of the two sets of commonlyused haze data,i.e.one based on meteorology phenomenon and another based on visibility+RH.The overall trends of the two sets are relatively consistent,only with a small difference in the averaged values.The correlation coefficients of the two data in different regions of China are all between 0.7 and 0.9.In addition,the effects of station screening and selection of relative humidity thresholds on hazeday trends were also analyzed and showed to be negligible.Based on evaluation of the haze data,the impact of the anomalous Arctic Oscillations?AO?on winter haze pollution in China from 1961 to 2017 was investigated.The results show that AO anomalies mainly affect meteorological conditions and winterhaze pollution in Northern and Central parts of China.In the years of abnormally high AO,surface temperatures were increased,precipitation frequencies were reduced and planetary boundary layer heights were suppressed,mainly driven by the weakening of the East Asian trough and the weakening of the Siberian high pressure.These meteorological anomalies effectively inhibited the horizontal and vertical diffusionof pollutants,finallyleading to an increase in winter haze day anomaly.In the low AO years,the situations were opposite but the impacts on meteorology were not as strong as in high AO years,with the winter haze day anomaly significantly reduced.The effect of AO anomaly on winter haze days was further studied using the WRF-CUACE model simulations.The results showed that the effect of AO anomaly on PM_2.5concentration was concentrated most obviously in central China,whichwas consistent with the data analysis.The impact mechanism was through the changes in regional depositions and transports.The affected depositionprocesseswere mainly shown in southern China and the dry deposition was more significantly affected by the AO anomaly than the wetdeposition.The effect of AO anomaly on the transport flux of pollutants was also reflected significantly in the southern region of China.In the year of abnormally high AO,the spreading conditions in central China were not conducive to further transports,leading to an i ncrease of winter haze day anomaly.In the year of low AO index,the transport fluxes in most southern areas were increased significantly and the overall diffusion conditions were better than those in the year with abnormally high AO.