Influence of Human Activities on Wintertime Haze-Related Meteorological Conditions over the Jing–Jin–Ji Region

This work analyzes and discusses the influence of human activities on the meteorological conditions related to winter haze events in Beijing,Tianjin,and Hebei(i.e.,the Jing-Jin-Ji region)during 1961-2016,using the results of two numerical simulation experiments based on the Community Atmosphere Model version 5.1.1(http://www.cesm.ucar.edu/models/cesm1.0/cam/docs/ug5_1_1/book1.html)used in the international Climate Variability and Predictability Programme(CLIVAR)Climate of the 20th Century Detection and Attribution Project(C20C+D&A).The results show that,under the influence of human activities,the changes in dynamical and thermal meteorological conditions related to winter haze events in the Jing–Jin–Ji region are conducive to the formation and accumulation of haze,and prevent the diffusion of pollutants.The dynamical conditions mainly include the obvious weakening of the East Asian winter monsoon(EAWM)and the enhancement of the near-surface anomalous southerly wind.The thermal conditions include the obvious increase in surface temperature,and the enhancement of water vapor transport and near-surface inversion.The relative contribution of dynamical and thermal conditions to the variation of haze days in the Jing-Jin-Ji region is analyzed using statistical methods.The results show that the contribution of human activities to the increase of haze days in the Jing-Jin-Ji region is greater than that of natural forcing for the study period.To be specific,the dynamical meteorological factors contribute more to the haze days than the thermal meteorological factors.The contribution of thermal meteorological factors is basically the same in both scenarios.