orogenicman
Darwin was a pastafarian
- Jul 24, 2013
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Arctic Oscillation:
Global Patterns - Arctic North Atlantic Oscillations AO NAO State Climate Office of North Carolina
Global Patterns - Arctic North Atlantic Oscillations AO NAO State Climate Office of North Carolina
The Arctic Oscillation (AO) is a climate index of the state of the atmospheric circulation over the Arctic. It consists of a positive phase, featuring below average geopotential heights, which are also referred to as negative geopotential height
anomalies, and a negative phase in which the opposite is true. In the negative phase, the polar low pressure system (also known as the polar vortex) over the Arctic is weaker, which results in weaker upper level winds (the westerlies). The result of the weaker westerlies is that cold, Arctic air is able to push farther south into the U.S., while the storm track also remains farther south. The opposite is true when the AO is positive: the polar circulation is stronger which forces cold air and storms to remain farther north. The Arctic Oscillation often shares phase with the North Atlantic Oscillation (NAO) (discussed below), and its phases directly correlate with the phases of the NAO concerning implications on weather across the U.S.
The North Atlantic Oscillation (NAO) consists of two pressure centers in the North Atlantic: one is an area of low pressure typically located near Iceland, and the other an area of high pressure over the Azores (an island chain located in the eastern Atlantic Ocean). It is important to note that these two locations are most commonly used to measure the NAO, but studies have found that the pressure centers move around on a seasonal basis, and other locations have also been used for measuring this index. Fluctuations in the strength of these features significantly alters the alignment of the jet stream, especially over the eastern U.S., and ultimately affects temperature and precipitation distributions in this area. It is also important to note that the AO and NAO are two separate indices that are ultimately describing the same phenomenon of varying pressure gradients in the northern latitudes and the resultant effects on temperature and storm tracks across the continent.