In the Northern Hemisphere, the main characteristics of the atmospheric circulation in the autumn (from September to November) of 2021 are as follows. The polar vortex is characterized by a monopole form and 5-wave mode in middle and high latitudes. In Eurasia, the circulation pattern of the westerly wind belt is adjusted greatly in the season. The subtropical high is strong and remarkably extends to the west. In autumn, the offshore gales in China are mainly caused by cold air, extratropical cyclones, and tropical cyclones. Among the 12 gale events above Beaufort scale 8, 8 are contributed by cold air, 6 by extratropical cyclones, and 4 by typhoons. A total of 9 typhoons are generated in western North Pacific Ocean and the South China Sea, of which 5 typhoons enter China's offshore areas. Influenced by the zonal band-shaped subtropical high, most offshore typhoons are active in southern oceans. A total of 18 tropical cyclones are named in the world's other oceans. There are 74 days of rough sea wave events with wave height greater than 2 m, which account for about 81% of the total number of days of the autumn. The rough sea wave events are closely related to gales. In autumn, China's offshore sea surface temperature is generally high. As the cold air gradually strengthens and becomes active, the sea surface in northern sea areas and coastal waters cools down rapidly. Thus the sea surface temperature gradient increases across the coastal areas, and the largest sea surface temperature gradient appears in the East China Sea.