The Effect And Mechanism Of Arctic Sea Ice In Autumn On The Interannual Variation Of Haze Pollution In North China In Late Winter

Haze pollution in the North China Plain is serious and consequently causes inconvenience in daily life and harms health.In this paper,we use the reconstructed haze days data,reanalysis data,data of Large ensemble simulations from the Community Earth System Model(CESM?LE),version 4 of the Community Atmosphere Model(CAM4)and Atmospheric Chemistry Model from the Goddard Earth Observing System(GEOS-Chem)to research the the mechanism and extent of the effect of East Siberian and Chukchi Sea ice on haze pollution in North China in late winter,which is conducive to the short-term prediction of haze pollution and the formulation of appropriate control strategies.It is found that large value region of haze days in early winter was concentrated in the south of the Yan Mountains,while the number of haze days in the east of the Taihang Mountains was less.The large value region of haze days in late winter is distributed along the south side of Yan Mountain and the east side of Taihang Mountain.This difference in the distribution of haze days between early and late winter is mainly caused by the difference of wind field near the ground.The haze days in early winter was significantly correlated with the southerly wind anomaly,while the haze days in late winter was closely correlated with the southeast wind anomaly.The number of haze days was declining before 2010 but then increased after 2010.The number of haze days in early winter has been changing at a considerably higher rate than those in February and March.The interannual variation of haze days in the North China Plain in late winter is closely related to the East Siberian Sea and Chukchi Sea ice in October,and the Pacific sea surface temperature(SST)plays a key role in delivering the effects of the sea ice on the haze.When the East Siberian Sea and Chukchi Sea ice increases in October,the October and November SST in the region over Minami-Tori Shima and Midway Atoll decreases.This reduced SST then lowers the January and February SST around the northwestern side of the Hawaiian Islands.The lower SST around the northwestern side of the Hawaiian Islands modulates the atmospheric circulation and makes the diffusion conditions and water vapor conditions near the ground more conducive to the accumulation and growth of pollutants.CESM?LE datasets validate the process whereby the East Siberian Sea and Chukchi Sea ice affects the SST in the aforementioned regions.The effect of changes in the SST around the northwestern side of the Hawaiian Islands on the meteorological conditions over the North China Plain was verified by numerical experiments using CAM4.The meteorological factors under different sea ice background was quantified using the GEOS-Chem model.Under the backgrand of high sea ice concentration,the wind speed in North China Plain is generally low,and the wind convergence zone is formed in the east of Taihang Mountain and the south of Yan Mountain.The specific humidity is 0.5 g/kg higher than that under low sea ice concentration background and the boundary layer height decreases by 58m,which increases the concentration of PM_2.5.Under high emission conditions,the average PM_2.5 concentration increased from 70.51?g/m³ to 104.18?g/m³,while under low emission conditions,the average concentration increased from 47.38?g/m³ to 66.57?g/m³.Under different sea ice background,the sensitivity of pollutants to emissions is also different.Emissions rose from the low scenario to the high scenario,the regional average concentration of PM_2.5 increased by 23.13?g/m³ under low sea ice concentration background and 37.61?g/m³ under high sea ice concentration conditions.In this experiment,the change of emission scenario has a more prominent contribution to the regional average concentration,while the contribution of meteorological factors will increase dramatically with the increasing of ?PM_2.5 concentration.