For a second year in a row, North America has shivered through a brutally cold winter – this year with the Northeast of the US bearing the brunt.
This weekend will be the fifth in a row that piles of snow have been dumped on Boston.
Laura Geggel, a staff writer at Live Science, has a good explanation of the science behind the big freeze, under the heartfelt headline “Why It’s So Freakin’ Cold”.
The freezing weather is part of a weather pattern that began last year, when the polar vortex, a system of cold air swirling around the Arctic, began pushing cold air into the United States. This pattern continued on and off throughout the summer, explaining the cooler temperatures in the eastern United States, said Bob Oravec, a forecaster at the National Weather Service.
This cold weather can take hold, thanks to flows in the middle and upper levels of the atmosphere that travel from northwest to southeast.
The Guardian spoke to Rutgers University climatologist Dave Robinson about the phenomenon.
Robinson said that cold from the vortex had shot south because of an opening in the jet stream, a westerly band of high winds that normally acts as a barrier between the arctic’s winter swirl and the milder weather of the lower 48 states. Every so often, he said, that band of winds will dip south over the eastern US, opening a window for a severe blast of frigid weather – in this case coming all the way from Siberia.
Is it the result of climate change? Robinson fears it might be.
He said that for 15-16 months the shifts in the jet stream and polar vortex have made “a very persistent pattern, and that’s when you start talking about a climate anomaly, as opposed to week-to-week weather variation.”
Bill Condie is a science journalist based in Adelaide, Australia.
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