Weather Station Hardware > Other Weather Station Hardware

Anenometer installation height

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scudwatcher:
Greetings from the CSRA!  I have a Davis Vantage Pro 2 Plus w/ 24 Hour FARS mounted to a 21 LF in length, chain-link fence 1.25 inches diameter top rail.  The Davis Instruments anemometer is installed at the top portion at a height of 19 Feet AGL.  The Davis Instruments ISS is mounted at a height of 5 Feet AGL.  The post was installed in the ground for at least 2 Feet below AGL.  Due to my REPRESENTATIVE station location, there is only minimal observed wind speed / direction difference from the previous anemometer height of 8 Feet AGL versus 19 Feet AGL.  My representative station location is in a residential subdivision with numerous trees.  My Local National Weather Service Forecast Office, Observations Program Leader approved my station location for performing Cooperative Surface Weather Observations.  Just install your anemometer at your station in the best location possible for your wind speed and direction data to be REPRESENTATIVE to your specific location.....Cheers.

johnd:

--- Quote from: scudwatcher on April 21, 2023, 09:56:21 AM ---...Just install your anemometer at your station in the best location possible for your wind speed and direction data to be REPRESENTATIVE to your specific location.....Cheers.

--- End quote ---

That is all very well, but rather ignores the fact that there is an official standard height for measuring wind speed which, as others have said, is 10m. And in a perfect world that is certainly the height to aim for.

But we all have to live with compromises and so the usual advice is simply to get the anemometer as high as is practicable for your given location and, perhaps more importantly, as distant from surrounding obstructions as possible. Only you will know about what is feasible for your own location but there is no doubt that the higher you can get the anemometer (safely and robustly, ie no long untethered poles that sway or vibrate strongly in the wind). The chart that Vasco provided gives you correction factors for different heights.

box:
Mines at 6 metres AGL

I think the important thing is horizontal clearance from trees and buildings

My site meets that requirement, but 6 metres is the length of poles and stays that I could afford/justify

If you get up to 10 metres you might start running into issues with planning or neighbours!

src:
Thanks for the various comments.

My proposed site is 50m from a single tree which is only about 5m tall. Other than the low stone wall (<1m) there are no buildings nor other trees within about 120m.

At this site I won't be able to fit guy ropes - the cattle in the field would trip over them and either pull the guys out of the ground or pull the mast down!

I have a 12ft long pole which is 42mm external diameter (1 2/3 inch). It is rather like a scaffolding pole but I think it is either an old handrail or piece of old iron heating pipe. It is quite heavy but also very rigid and will not sway in the wind.

I propose to secure it to the gatepost using two of these:

https://cpc.farnell.com/blake-uk/wb20-g/6-x6-standoff-wall-brkt-galvanised/dp/AP00962

I may let the lower end of the pipe rest on a rock on the ground to take some of the weight.

To the top of this Iíll clamp a 6ft x 1inch pipe on top of which I can secure my Ecowitt WS90 (which is designed to fit on top of a 1inch mast).

With an overlap of 1 foot where the two poles are strapped together Iíll end up with a mast reaching 17ft (5m) which I think is enough. Iíll set correction to 10%.

With only 5ft of thinner pole being unsupported hopefully there will be little wind-induced sway. If there is significant sway I could lower the top pole and restrap the two poles with a much larger overlap and a shorter top section.

Iíll let you knowÖ

box:
I think you may be surprised by the amount of movement

I tried mine unstayed for a month or so. It only had a WS68 on it, not a full station but it certainly moved around!

It's aluminium poles though so you may have more success with yours as they sound more substantial

What are you packing the gap with or does the smaller pipe slide inside the larger one with no gap?

I'd watch that gatepost too, there is a big turning moment from a tall mast, a lot more than from a gate.. :shock:

Good luck!!

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