By John Weiss

Post-Bulletin, Rochester MN 

WINONA -- If Toby Dogwiler was asked to teach Wind 101, the Winona State University geoscience professor would make sure students knew these basics:

• Wind is the horizontal movement of a fluid. "Air is a fluid, just like water," he said.

• It gets its energy from the sun that heats the surface of the earth unevenly, creating places where it's warmer and the air rises, so air from the outside moves in. "It's essentially a solar-powered system."

• It doesn't move evenly, so wind is better at turning wind turbines in some places than others. Wind doesn't always blow nor does it always blow hard.

The strongest winds are often where centers of high and low pressure are close, he said.

In high-pressure systems, cold air sinks down and pushes outward at the earth's surface. Low-pressure systems are where the warmed air is rising from the surface. Air from the highs moves toward the lows; the closer they are, the stronger the winds. As that air rises, it cools and will eventually fall. As the cooler air warms, it will rise again. It all forms a cycle, Dogwiler said.

In the real world, it's not that simple, he said. Wind direction and strength are also affected by the jet stream and other dynamics in the upper atmosphere.

Differing winds

In the real world, not all wind is created equal for wind power, Dogwiler said.

The critical requirement for good wind power is flat land where the wind has a chance to get a run at the wind turbines, he said. That's why there are so many turbines in the southwestern part of the state and there are more in the flat western part of this region he said.

"It's flat; it's easy for wind once it gets blowing to keep moving," he said.

Also, weather patterns farther west into the Dakotas and Great Plains are much more variable, Dogwiler said.

The plains of Canada are a great place for cold fronts to grow because the land is flat and homogeneous. Once the jet stream finally moves south, the cold comes down to us.

Battleground of fronts

The plains also get warm fronts from the Gulf of Mexico, and when the cold and warm fronts collide, it's like a big battleground between the two fronts. The result is a lot of storms and a lot of wind.

In the blufflands, however, with all the trees and rocks, winds are slowed and swirled so they don't have the consistent power, he said. Or they keep changing directions as they hit obstacles such as bluffsides.

Trees are especially important for blocking wind, said Mike Fuhs, a meteorologist with the National Weather Service in Sioux Falls, S.D.

The best winds in the state -- the first place where wind farms were built in Minnesota -- are at Buffalo Ridge, a crescent of land mostly in Lincoln and Nobles counties in the southwestern corner. That has a bonus, he said. Most of the land there is about 1,400 feet above sea level, but the ridge is 1,800 to 2,000 feet, and that helps a great deal because winds are stronger higher up.

Finally, there is a low-level jet stream that begins in central Oklahoma and extends into South Dakota and western Minnesota, where winds also blow strong at night instead of tapering off, he said. That stream blows over Buffalo Ridge.

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