Author Topic: Anemometers, installing above ground level, how about surrounding tree level?  (Read 367 times)

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Offline DaleReid

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I know the publications on how high to install an anemometer above ground to give the established level to measure wind speed locally.  The surrounding area should be open and clear, when possible.

Without disturbing domestic tranquility in my household, by cutting down lots of trees, I'm stuck with some oak forest regrowth where we live.

To fly over in a plane, it is amazing how little each home has cleared out around it, with the roof and some driveway or maybe some backyard allocated to each home.  The surrounding area is over 1/4 mile by 1/2 mile of thick oaks and a few other trees scattered in.

I've turned to moving my wind monitors further up a tall amateur radio tower, which is nice but brings a question.

When I have the guys with 'nads to climb my tower and install the sensors, I asked them to get at least above the level of the tree tops.  With the clearing around the house, and approximately centered for the tower, I thought I'd be measuring a good approximation of wind at the 33' level suggested in the perfect installation guide from the weather service.

I guess what I'm wondering, in other words, is if one looks at wind speed measured at increasing height above ground, it does pick up and continues to show faster speeds as one gains elevation over BARE GROUND.  What effect does having a tree top level do for wind measurement? 

I'm guessing that the wind at tree top level is higher than near ground, and one can't just assume that going 30 feet higher than the trees is the same as an open ground area with the monitor 30' up. 

My installations show much less variation in wind direction caused by turbulence.  But what affect is caused by the one sensor at about 70' above ground, but only 15' above the average (and they are pretty average) tree tops?

Thoughts?   Dale
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Offline ocala

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I "think" that in a recent discussion on here someone posted a graph of  wind speeds at different elevations but I don't think it took into account turbulence at tree top level. I briefly looked for it but couldn't find it.
Also I believe Weather Display has an off set feature you can apply to wind speed. Not a 100% sure of that though.
You can also look at this link.
https://www.researchgate.net/post/How_we_can_realistically_calculate_wind_speed_at_higher_altitudes

Offline PaulMy

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I "think" that in a recent discussion on here someone posted a graph of  wind speeds at different elevations but I don't think it took into account turbulence at tree top level.
Correct http://www.wxforum.net/index.php?topic=2753.msg23357#msg23357  http://www.wxforum.net/index.php?topic=34010.msg345548#msg345548  ;)

Enjoy,
Paul