Global view on China's foggy-haze associated with air-pollutant conveyor belts.

Upper air and surface data from 1960 to 2016, NCEP reanalysis from 1990 to 2016, air composition data from 2015 to 2016, and data from the drift automatic weather station in the Arctic from August 2012 to February 2013 are used to analyze the heavy foggy haze in China from a global perspective. Our findings show that sensitive foggy haze in winter is located in the eastern region of China because of the comprehensive effect of multi-factor meteorological conditions and the response to climate change under global warming as follows. (1) For the past half-century, two winter monsoon airflows blow from the East Asian continent and adjacent sea to North China. The airflow in the intermediate zone (North China) between the two winter monsoon airflows generates a retained circulation owing to the Earth's rotation because wind velocities over land and sea are different and their wind intensities are weakened. The circulation retention index has been on the rise in recent years, causing a “static stability” that retains or stabilizes air masses over this area. (2) Under global warming, polar ice has shrunk to a historical lowest over the years. The melting polar ice results in explosive heating and humidification in the lower troposphere leading to increased aerosol concentrations, which is conducive to maintaining or strengthening the Arctic haze. (3) The two winter monsoon pathways run over the Eurasian continent and the surface of the adjacent Sea of Okhotsk, thus affecting North China. These results are consistent with the airflow of the pollutant conveyor belt channeling from the Arctic haze zone. As a result, the pollutant conveyor belt from the Arctic haze zone as well as the pollutant conveyor belts from West Asia and North Africa contribute substantially to the high frequency of winter foggy haze over eastern China.