The Arctic Oscillation(AO) or the Northern Hemisphere Annular Mode(NAM),which is one of the important modes of climate variability,is usually represented by the leading EOF of Northern Hemisphere variability.

• 作为一个全球气候变率的重要模态,北极涛动或北半球环状模态(AO/NAM)一般由北半球海平面气压变率的EOF1来表示。