Siberian snow has long-range effects

One of the Northern Hemisphere’s long-lived, winter-weather features is the so-called Siberian high. As winter deepens, this dense mass of cold air becomes a potent weather maker for the Arctic and even temperate North America.

In the Jan. 15 Geophysical Research Letters, scientists report that the strength of the Siberian high is linked to the amount of early-season snow cover in this Russian region. The researchers, led by Judah Cohen of the consulting firm Atmospheric and Environmental Research in Lexington, Mass., made the connection after analyzing data collected from 1972 to 1999.

As autumn arrives in northern Eurasia, the Siberian high begins to form and then strengthen. Because the dense air typically extends only a few thousand feet high, it usually doesn’t cross over the mountains into eastern and southern Asia, Cohen says. Instead, it moves westward into Europe.

After the Arctic Ocean freezes over in early winter, the high-pressure area can spill across the ice-covered North Pole to refrigerate North America. A surge of this bone-chilling air-often called a Siberian express-can sweep along at up to 60 miles per hour and make temperatures plummet 10ºF to 20ºF in a few minutes.

The researchers’ analysis showed strong correlations between the amount of Siberian snow cover in October and the strength of the Siberian high in December through February. When snow falls early in Siberia, quickly dropping air temperatures and high barometric pressures may strengthen the developing high. Awareness of this new link could improve winter-climate predictions for much of the Northern Hemisphere, Cohen notes.

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