Using the daily records derived from the synoptic weather stations and the NCEP/NCAR and ERA-Interim reanalysis data, the variability of the winter haze pollution (indicated by the mean visibility and number of hazy days) in the Beijing–Tianjin–Hebei (BTH) region during the period 1981 to 2015 and its relationship with the atmospheric circulations at middle–high latitude were analyzed in this study. The winter haze pollution in BTH had distinct inter-annual and inter-decadal variabilities without a significant long-term trend. According to the spatial distribution of correlation coefficients, six atmospheric circulation indices (I₁ to I₆) were defined from the key areas in sea level pressure (SLP), zonal and meridional winds at 850 hPa (U850, V850), geopotential height field at 500 hPa (H500), zonal wind at 200 hPa (U200), and air temperature at 200 hPa (T200), respectively. All of the six indices have significant and stable correlations with the winter visibility and number of hazy days in BTH. In the raw (unfiltered) correlations, the correlation coefficients between the six indices and the winter visibility (number of hazy days) varied from 0.57 (0.47) to 0.76 (0.6) with an average of 0.65 (0.54); in the high-frequency ( < 10 years) correlations, the coefficients varied from 0.62 (0.58) to 0.8 (0.69) with an average of 0.69 (0.64). The six circulation indices together can explain 77.7 % (78.7 %) and 61.7 % (69.1 %) variances of the winter visibility and the number of hazy days in the year-to-year (inter-annual) variability, respectively. The increase in I_c (a comprehensive index derived from the six individual circulation indices) can cause a shallowing of the East Asian trough at the middle troposphere and a weakening of the Siberian high-pressure field at sea level, and is then accompanied by a reduction (increase) of horizontal advection and vertical convection (relative humidity) in the lowest troposphere and a reduced boundary layer height in BTH and its neighboring areas, which are favorable for the formation of haze pollution in BTH winter, and vice versa. The high level of the prediction statistics and the reasonable mechanism suggested that the winter haze pollution in BTH can be forecasted or estimated credibly based on the optimized atmospheric circulation indices. Thus it is helpful for government decision-making departments to take action in advance in dealing with probably severe haze pollution in BTH indicated by the atmospheric circulation conditions.

In addition to weather conditions and pollutant emissions, the degree to which topography influences the occurrence and development of haze pollution in downtown Beijing and the mechanisms that may be involved remain open questions. A series of atmospheric chemistry simulations are executed by using the online-coupled Weather Research and Forecasting with Chemistry (WRF-Chem) model for November-December 2015 with different hypothetical topographic height scenarios. The simulation results show that topography exerts an important influence on haze pollution in downtown Beijing, particularly the typical development of haze pollution. A possible mechanism that underlies the response of haze pollution to topography is that the mountains that surround Beijing tend to produce anomalous southerly winds, high relative humidity, low boundary layer heights, and sinking motion over most of Beijing. These conditions favor the formation and development of haze pollution in downtown Beijing. Furthermore, the reduction percentage in PM_2.5 concentrations due to reduced terrain height in the southerly wind (S) mode is almost three times larger than that in the northerly wind (N) mode. In the context of the regional topography, the simple S and N modes represent useful indicators for haze prediction in Beijing to some extent, especially over medium to long time scales.

In this study, the possible influence of the Antarctic oscillation (AAO) on winter haze pollution (indicated by atmospheric visibility after rain, fog, dust, snowstorms, etc. are removed) in North China (NC) was investigated. The results show that the mean winter visibility (December‐January‐February visibility) throughout most of eastern China is negatively correlated with the preceding AAO (August‐September‐October (ASO)‐AAO), especially in NC. The interannual correlation coefficient between DJF‐VIS in NC and the ASO‐AAO is −0.52, which is significant at the 99% level. The negative correlation suggests that an enhancing (weakening) ASO‐AAO could be conducive to increases (decreases) of haze pollution in NC in boreal winter. The responses of local and regional meteorological conditions to the ASO‐AAO support the relationship between the ASO‐AAO and winter air pollution in NC. A preliminary mechanism analysis shows that a positive ASO‐AAO may induce a sea surface temperature warming tendency in the Northwestern Southern Indian Ocean. This warming then causes a wave train‐like pattern in the upper troposphere along the jet stream and an anomalous zonal cell that weakens the regional Hadley circulation from the Maritime continents to East Asia. All of these factors are favorable to the formation of anomalous southerly and haze pollution in NC.

During the past few years, air pollution in the Fenwei Plain (FWP) region had obviously rebounded. In this study, we used quantitative analysis, difference analysis, and correlation analysis methods to analyze the temporal and spatial distribution and the influence of the meteorological and climatic factors on haze pollution in FWP. The results showed that on the long‐term timescale, the haze pollution had an overall upward trend during the winter of 1984–2017, and the pollution became more serious after 2000. In addition, the differences in meteorological parameters such as relative humidity, sea level pressure, temperature, vertical velocity, and wind fields near the surface between the regional haze days and the regional clean days were remarkable, indicating that the changes in these meteorological parameters had a distinct impact on haze pollution. Among several atmospheric circulations in the Northern Hemisphere mid‐high latitudes, Eurasian (EU) pattern had the most obvious influence on haze pollution via two possible pathways: First, on the interannual timescale, the evolution of EU pattern affected the changes of Siberian high and Aleutian low pressure; second, changes in EU pattern could result in changes in wind speed at 850 hPa, boundary layer height and relative humidity in the lower troposphere. All these findings may provide some help for the government to take prevention measures for haze pollution in FWP.