2021年秋季海洋天气评述

Autumn 2021 marine weather review

2021年秋季(9—11月)北半球大气环流特征为:极涡整体呈单极型,中高纬环流呈5波型分布,欧亚地区西风带环流形势季节内调整大,副热带高压(以下简称“副高”)偏强,西伸明显。秋季我国近海大风过程主要由冷空气、温带气旋和热带气旋影响造成。在12次8级以上大风过程中,冷空气影响8次,温带气旋影响6次,台风影响4次。西北太平洋和南海共生成9个台风,其中5个台风进入我国近海,在东西带状分布的副高影响下,近海台风主要活跃于南部海域;全球其他海域共命名热带气旋18个。我国出现2 m以上大浪过程的日数为74 d,约占总日数的81%,大浪过程与大风过程联系密切。秋季我国近海海面温度整体偏高,随着冷空气的逐渐活跃,北部海区和沿岸海域海面降温迅速,沿岸海面温度梯度加大,我国近海海域中,海面温度梯度最大的区域出现在东海。

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.