I should have known better. A thousand feet above the nearest tree was not the place to pitch a tent named “Timberline.” I had waited out many a northern storm inside this tent, crammed in way too many card-game compatriots, even proposed to my wife inside. But my old warhorse was no match for the unbridled wind that blasted my campsite on Canada’s Caribou Mountain. First the door popped. Then the poles snapped. After several hours of lying there, the collapsed roof flapping crazily in my face, I felt sure my sanity would be the next thing to go.
“People underestimate the wind,” says naturalist Jan DeBlieu, author of Wind: How The Flow Of Air Has Shaped Life, Myth And The Land. “Its swings of mood are devilishly tricky to foretell.” True enough, yet there are some facets of wind that we can rely on with certainty. For instance, it’s safe to assume the kind of mountain winds I encountered above treeline in the Yukon Territory will, indeed, rip a decrepit old three-season tent to shreds.
We also know that wind is a complex element of nature, a collection of forces that have one simple origin: the sun. Where the sun shines longest and strongest, the ground is warmed, air rises above it, and cooler air flows in to fill the vacuum. In other words, wind is essentially the flow of air from cool regions to warmer ones. Expand that concept to global proportions, and you’d probably think that warm air at the equator rises, the equator sucks cold air from the poles, and thus, that all air flows north or south. Not quite. Like I said, wind is a complex force of nature.
The Earth’s winds stem from a complicated interaction of the planet’s rotation and the constant heating and cooling–and, therefore, rising and falling–of air at every latitude. The net effect for North America is surface winds that flow reliably from west to east, with influxes of cooler Arctic air mixed in and creating more volatile weather fronts to keep things interesting.
Finally, there are the effects the Earth’s surface has on wind. Example: Air heats more quickly over land than water, as well as over certain types of land, such as deserts. Uneven heating, combined with the disruptive effects of changing topography, create a jumble of airborne eddies that often defy understanding.