Influences Of Atmospheric Intraseasonal Oscillation In Mid-High Latitudes On Winter Haze Pollution Over The Beijing-Tianjin-Hebei Region

As a typical region with dense population and high degree of industrialization,the air pollution over the Beijing-Tianjin-Hebei(BTH)region is becoming more and more serious,which seriously affects the health of local residents and restricts the development of regional economy.Based on the data of haze day from CMA and NCEP-DOE reanalysis data,this thesis analyzes the intraseasonal evolution of the winter haze pollution over BTH region in China between 1979 and 2013,and the influences of the atmospheric intraseasonal oscillations(ISOs)in mid-high latitudes.In addition,the interannual variability of the atmospheric intraseasonal oscillation intensity of haze pollution over the BTH region on winter,and the influences of large-scale background fields were also discussed.First,a case analysis of haze pollution event over the BTH region in the winter of2013 shows that there is significant intraseasonal variation of haze pollution in that year,and an eddy vorticity train formed by alternating anomalous low pressure and high pressure centers in the mid-high latitudes influences the haze pollution over the BeijingTianjin-Hebei region.Following the statistical analysis of all winters from 1979-2013,two significant ISO signals of 10-20-day and 20-40-day are identified from the winter haze pollution over the BTH region,and their superposition notably contributes to the occurrence of haze pollution.On the 10-20-day timescale,the haze pollution is intimately associated with a mid-high-level southeastward-propagating wave train that originates from the north Atlantic.With the wave evolution,an anomalous anticyclone reaches the Korean Peninsula-Japan,leading to strong descents and anomalous southerly winds over the BTH region,favorable for haze pollution.On the 20-40-day timescale,the atmospheric wave train in the mid-high latitudes originates from the eastern North America,propagates eastward to the northwestern Lake Baikal,and then turns southward to the northeastern China-Japan.The peak stage of the haze pollution is related to the resultant zonal dipole,with the anomalous cyclone over the northwestern Lake Baikal and the anomalous anticyclone over the northeastern China-Japan.The dominance of the mid-upper tropospheric anticyclone over the BTH region suppresses the development of convection,thus hindering the vertical diffusion and wet deposition of pollutants.Moreover,the anomalous westerly winds between the dipole weaken the incursion of cold mass from higher latitudes,thus further contributing to the peak of haze pollution on the20-40-day timescale.Further analysis shows that there is a significant interannual variation in the variance contribution of intraseasonal variation of different periods of winter haze pollution over the Beijing-Tianjin-Hebei region from 1979 to 2013.The classification composite analysis reveals that on the interannual scale,when the polar vortex is enhanced(weakened),the Arctic Oscillation/North Atlantic Oscillation index is strong(weak),the 10-20-day intraseasonal oscillation enhanced(weakened)while the20-40-day intraseasonal oscillation weakened(enhanced),which is probably to be related to the high(less)Arctic sea ice concentration in autumn,and the Eurasian snow anomaly in autumn may also play a role.