A monthly column in the Monadnock Ledger-Transcript.

Friday, October 22, 2010

The Wind

Bobcat’s Tail - October 2010 - A collaboration with the Monadnock Ledger-Transcript.

By Eric Aldrich

There’s a Lot Riding on that Wind

Barely a day goes by when we’re not touched by the wind.
It may be a soft puff from an open window. Or a gentle breeze that tousles our lover’s hair. Or a stiff November wind that sways the trees. Or – thankfully rare – the brutal impact of a hurricane.

What is Wind?
Though seldom asked, Stacey Kawecki at the Mount Washington Observatory defines wind as “the equalization of pressure in the atmosphere. You get wind from the difference between high pressure to low pressure on the horizontal plane.”
Always, somewhere on in the world, there is wind. Outside your home on any given morning, however, you may notice no wind. The hair on your head, the leaves on the trees or even the most sensitive equipment may detect no wind at all. Nothing. But minutes or hours later, as the sun rises and temperatures rise and pressures start to change, there’s likely to be wind, if only a little.

Measuring Wind
            Meteorologists tend to measure wind in miles or knots per hour. At the Mount Washington Observatory – on the summit of the Northeast’s highest peak – they had the fearful distinction of measuring a wind gust at 231 mph in April 1934, setting a world record for surface wind speed.
            That would be way, way off the scales of the Beaufort scale, which is a way to classify wind speeds. The Beaufort scale runs from zero to 14. Zero is calm, or less than 1 knot over a 10-minute period. Between one and three are described as “light air” to “gentle breeze.” Seven on the scale is a moderate gale. Eleven (at 55 to 63 knots) is described as a storm. And 12 to 17 are hurricane-force winds, with 17 being a scary category 5 hurricane at 120 knots.

Cosmic Wind
            If you think that’s windy, try living on Neptune! On the planet’s southern latitutudes, one high-speed jet stream travels at 670 mph! At cloud-top levels on Neptune’s equator, the prevailing wind speed is an estimated 890 mph! Try flying a kite in that breeze.
            Solar wind is entirely different than atmospheric wind from a planet. Streams of charged particles are ejected from the sun’s upper atmosphere. This plasma flies off the sun at 890,000 mph. One consequence of these solar winds is the Northern lights or aurora borealis. Look for them often and, if you’re lucky, you’ll see them.

Wind in the Woods
            Back on comfortable old Earth, it’s easy to take the wind for granted. But it has a huge impact on our landscape, and not just on the ocean’s waves or the desert’s dunes. The wind influences our forest in many ways, both subtle and not-so-subtle, according to Steve Roberge, forest educator for UNH Cooperative Extension Service in Cheshire County.
            Wind aids in pollination and seed dispersal of a vast number of trees and other plants, Roberge says. On a windy day in late spring, you can see clouds of pollen drifting from the tops of white pines. Cones of pines, spruce and other conifers have adapted to the effects of the wind. Roberge points out how wind spins around the cone, sucking out pollen and carrying it off.
            In the forest, the wind also creates a phenonmenon called “crown shyness.” Look up into the forest canopy and sometimes you’ll see spaces between the trees – a gap where one tree’s crown stops and the neighboring tree’s crown begins. The gap is the “shyness,” caused over time as the wind sways the trees, bumping and abrading the extended limbs. Wind shaking a strong red oak, Roberge says, can easily muscle the surrounding paper birch into submission.

Wind in the Wild
            Wind provides the energy to transport sailors, countless bird species and insects. Birds use wind corridors as conveyor belts for migration. Ornithologists have long known that many birds even shift their altitude to maximize their flying efficiency.
            More recently, scientists have discovered that insects do the same thing. Long thought to be at the whim of the winds, moth and butterfly species apparently detect wind speed and direction at different altitudes and can adjust their flights accordingly to get the best mileage, according to a recent study in Science magazine.
"Because insects fly slower than birds, they had to evolve a way to increase their speed," says study author Jason Chapman of Rothamsted Research, the agricultural research institute in Harpenden, England. "The way they've done this is to really exploit the wind." With good winds, moths are faster than birds, Chapman says.

Huddling and Hunting
            Wind affects the way wildlife behave even when species are not migrating. It knocks acorns and other seeds to the ground, giving food for squirrels, deer, wild turkey, black bear, moose ... the list goes on. Severe wind will cause some species to huddle together for warmth, including turkeys. Think about those images of penguins in Antarctica, huddled together in the fierce winds, occasionally shifting around so the ones on the edge aren’t constantly feeling the impact.
            And as any hunter knows, wind can have a huge impact on predator-prey relationships. A white-tailed deer can easily detect a potential predator (human or otherwise) when the wind carries a suspicious scent to its nose. The wind’s noise can become an advantage to a predator and a distinct disadvantage to its prey.
            The next time you step outside, ask yourself what's riding on that gentle breeze. The answer, my friend, is blowing in the ...
Eric Aldrich writes from his home in Hancock.