Between the Lines

Between the Lines by David Lias Those days of a 70-below windchill factor in South Dakota are almost surely a thing of the past.

I'm not saying this because of global warming, or the fact that on the eve of Thanksgiving it feels more like spring outside (while I puttered around town running errands, my car actually began to overheat Wednesday).

No, when winter finally strikes, it will, at least according to the weatherman, seem more bearable. The windchill factor, you see, no longer will be quite as, well, chilly.

The National Weather Service is revising how cold it feels in a given combination of temperature and wind strength.

In the past, the agency measured windchill at an altitude of 33 feet. Now readings will be taken at 5 feet above the ground, where most of us actually feel the arctic gusts biting our faces in January and February.

For example, with the temp at zero and wind at 20 miles per hour, the windchill would be 39 below under the old formula. Today, it would be 22 below.

According to meteorologists, we may never encounter a 70-below windchill in South Dakota again. The result of this change may be a redefinition by all of us on just exactly how cold our winters are.

Personally, a windchill of about 1 below zero is just as severe as one that hits the 70-below mark.

Stepping out in a frigid South Dakota wind, no matter the accompanying chill, really isn't much different than standing on the end of diving board and jumping into a pool.

Every time you take that leap, you know you'll get wet from head to toe. Every time you step outside into the teeth of a howling Canadian blast here on the plains, you know you'll soon be numb � no matter what the windchill is.

For decades, the windchill factor � which combines air temperature and wind speed for a reading of what it supposedly "feels like" � has been a staple of winter weather forecasts, especially in South Dakota.

I've seen charts and graphs and other data that shows how to determine the windchill, but I've always been a bit curious about this meteorological concept.

It turns out that a change in the windchill factor has been a long time coming. It was created during an Antarctic expedition in the 1940s by U.S. Army Maj. Paul Siple, a geographer, and geologist Charles F. Passel.

The two researchers hung plastic cylinders of water in the open air and measured the rate at which the water froze as temperatures and wind speeds changed. The Weather Service adopted the windchill index in 1973. But for decades, scientists have been concerned that the formula overestimates how cold it actually feels.

Last year, the Weather Service appointed Maurice Bluestein, an engineering professor at Indiana University-Purdue University in Indianapolis, and Randall Osczevski, an environmental physicist with Canada's Defense Department, to develop a new system combining studies they had done independently over the years.

This summer, a dozen volunteers participated in a two-month study in Canada to examine the body's heat loss in simulated windchill conditions (what a fun way to spend your summer vacation). The researchers focused on the face and head, the most exposed surfaces and most likely to suffer frostbite or cause hypothermia.

They presented their findings to American and Canadian weather officials, who approved them for both countries last summer in Toronto.

The new windchill system shows that humans generate heat, unlike the plastic cylinders used in the Siple-Passel model, Bluestein said.

He added that the current windchill index also ignores human activity, not to mention sunshine and humidity. The sun's rays can make air temperature feel 10 degrees warmer, he said.

It's rather difficult to take comfort in the professor's observation, even if they are correct

Starting this month, the public "will see warmer, more accurate readings, but the weather won't change," Bluestein said. "It will still be cold."

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