Jump to content Jump to footer
Install App

Install this app on your device for a better experience.


The English version of our glossary is currently under construction and will be regularly updated.

Northern Annular Mode (NAM)

The Northern Hemispheric Annular Mode (NAM, also Arctic Oscillation (AO)) is a manifestation of sea-level pressure differences between the Arctic and the middle latitudes of the Northern Hemisphere.

The winter variations in a weather pattern characterised by low sea-level pressure in the Arctic and powerful westerlies in the middle latitudes. The NAM is connected to the stratosphere by the northern polar vortex. Closely related to the North Atlantic Oscillation.