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Old 15-09-2011, 13:19   #1
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Help Me Understand Average Wind Speed Readings

My handheld anemometer will measure average wind speed in 5, 10 and 13 second intervals. What is singificant about the different intervals and why would I choose a particular interval over another?
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Old 15-09-2011, 13:23   #2
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Re: Help me understand avg wind speed readings.

Usually there is average, peak and instantaneous. It's all a matter of what you find useful.
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Old 15-09-2011, 13:51   #3
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Re: Help me understand avg wind speed readings.

I was wondering if it had something to do with time between waves or something like that.
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Old 15-09-2011, 13:55   #4
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Re: Help me understand avg wind speed readings.

I don't know. I have never heard of taking wind averages like that.
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Old 15-09-2011, 14:13   #5
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Re: Help Me Understand Average Wind Speed Readings

As with pretty much any instrument, it's all about getting rid of meaningless noise. Especially for a handheld, instantaneous measurements can be full of inaccuracies. Is your hand moving? How fast? What direction? How about your platform (boat). Going up a wave face, down one. The selection of which time period should be based on what you observe about the measurements you are taking and what cycles you can discern.

Curious about the actual periods they provide though - 5,10,13. Those are not any standards that I know of in the meteorological world. The "3-second gust" is used very widely in engineering design and met. record keeping. From there the next standards are almost always 1 minute and 10 minute. So, the 5,10,13 seem like they were selected somewhat at random to allow you to remove signal noise. I'd love to hear if it was other than random and what the reasoning was.
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Old 15-09-2011, 15:23   #6
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Re: Help Me Understand Average Wind Speed Readings

FWIW,

In Australia, the wind speeds predicted or reported by the Met office are averaged over ten minutes. The resulting numbers are a lot lower than the numbers reported by yotties who peer at their anemometers (uncalibrated at that) every now and then, concentrating on the scary gusts. We don't have any useful means of measuring these average winds, and the averaging periods that you mention are as mentioned above, just to take out short term variations.

Oh, in Oz, every broadcast of the wx starts out with the warning that predicted winds are averages and that peak winds may be 40 % stronger. I think that no one listens...

Cheers,

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Old 15-09-2011, 15:50   #7
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Re: Help Me Understand Average Wind Speed Readings

NOAA uses "Sustained winds are defined as a 1-minute average wind measured at about 33 ft (10 meters) above the surface."
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