Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences Fudan University Shanghai 200438 ChinaKey Laboratory of Regional Climate-Environment for Temperate East Asia Institute of Atmospheric Physics Chinese Academy of Science Beijing 100029 China;
Key Laboratory of Regional Climate-Environment for Temperate East Asia Institute of Atmospheric Physics Chinese Academy of Science Beijing 100029 China;
Arctic sea ice; Greenland blocking; Meridional gradient of potential vorticity; Extreme cold weather;