To understand the complicated relationships between synoptic forcing, regional transport and aerosol pollution during the same period of the Beijing Olympic and Paralympic Winter Games in history from 2015 to 2019, long-term meteorological observations, aerosol measurements and radiosonde data in Beijing and Zhangjiakou were analyzed, in combination with numerical simulation and objective synoptic classification. It’s found that the heavy aerosol pollution in both Beijing and Zhangjiakou is associated with warm, moist, and calm wind situations at the ground level. At the upper level, the heavy pollution events in Beijing are related to the 850 hPa southwest winds, and the heavy pollutions in Zhangjiakou are typically associated with the southwest and south winds. Although the distance between the centers of Beijing and Zhangjiakou is around 160 km, the increasing aerosol concentrations and occurrence of thermal inversion aloft are often synchronously observed in those two cities, which are relevant to certain large-scale synoptic patterns. When there is a high-pressure system in eastern China at the 850 hPa level, the warmer air mass in the southern regions can be brought to Beijing and Zhangjiakou, enhancing the thermal inversion and suppressing the development of boundary layer to some extent. Meanwhile, the aerosols emitted from the south Hebei, the north Shanxi and middle Inner Mongolia can be transported to Beijing, leading to the exacerbation of pollution. With a higher altitude, the polluted air masses advected to Zhangjiakou are mainly from the western upstream regions, which can deteriorate the air quality in addition to the local emissions. Thus, under the unfavorable synoptic conditions, joint efforts to reduce emissions in Beijing, Zhangjiakou, and those upstream regions should be considered to effectively mitigate the heavy pollution.

To understand the meteorological characteristics associated with the prolong low-visibility events occurring in Haikou and Qiongzhou Strait during February 2018, we systematically analyzed the visibility data, surface meteorological observations, sounding data and reanalysis data. It’s found that the low-visibility events in winter in Haikou typically occurred under relatively warmer and moister conditions. In winter, the visibility of Haikou was significantly anti-correlated with relative humidity, temperature and thermal stability, and was significantly correlated with wind speed and boundary layer height. No significant correlation was found between visibility and PM_2.5 concentration. At the 925 hPa level, when Haikou was located to the south of high-pressure system, good visibility could be observed associated with the northeasterly winds; in contrast, when Haikou was controlled by the southeasterly winds, the warm and moisture air mass could be brought to Haikou, favoring the occurrence of low-visibility events.