Pine tree effect

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A cloudy Highway 1 near Ely today. On sunny days, pine trees in coniferous forests can create warmer microclimates "up north."

It's good to get away to northern Minnesota for us city folk.

My weekend in the Brainerd Lakes area was full of fun and relaxation as usual. A cool foot of snow still covers the ground, much to the delight of snowmobilers. The northern landscape still lies in winter's grip, but signs of seasonal change can be seen with a sharp eye.

The higher late February sun melts away road surfaces much faster now. And if you stand on the sunny side of a pine tree, even when it's 15 degrees it feels pretty nice if there's no wind. That's because you're standing in a microclimate. The sun's rays bounce off the tree, converting the radiation from short wave to longer wavelengths. These longer wavelengths are more effective at heating the surrounding air and you feel warmer.

Now multiply that effect by what, 100 million pine and spruce trees in northern Minnesota? You can see why on sunny, calm days in northern Minnesota in late winter thermometers respond with warmer temps than in the metro or the farm fields of the south. Even in the same air mass it's often warmer up north.

You can thank "Big Al" or albedo for the difference. A snow covered landscape will reflect about 80 to 90 percent of the sun's energy back into space. A coniferous forest only reflects back about 10 to 15 percent. The rest of the energy is available to heat the surrounding air.

We live in an amazing state. There is always plenty of weather and scenery to enjoy!

PH

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