Snow Job

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Science  04 Apr 2003:
Vol. 300, Issue 5616, pp. 19
DOI: 10.1126/science.300.5616.19b

The largest source of year-to-year variability of winter weather in the extratropical Northern Hemisphere is an oscillating pattern of atmospheric pressure that has poles near Iceland and in the subtropical North Atlantic, commonly called the Arctic Oscillation/North Atlantic Oscillation (AO/NAO). The AO/NAO directs the tracks of storms crossing the Atlantic, affecting temperature and rainfall in North America, Europe, and northern Asia. It has been thought that the pattern of interannual variability of the AO/NAO is random and a consequence of the internal dynamics of the climate system. However, it also has been noted that, over the past 30 years, the AO/NAO has exhibited a trend; this has led to the proposal that it is modulated by soil moisture, secular changes of atmospheric greenhouse gas concentrations, sea-surface temperatures, the stratosphere, or sea-ice cover. Saito and Cohen add another ingredient to this olio by showing that continental-scale snow cover in North America and Eurasia varies with the atmosphere, leading the atmosphere by several months and influencing the AO/NAO on annual to decadal time scales.—HJS

Geophys. Res. Lett.30, 1302 (2003).

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