Author Topic: Anemometer photos- and questions about my setup  (Read 9312 times)

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Offline NorthNJwx

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Anemometer photos- and questions about my setup
« on: March 21, 2008, 10:20:49 AM »
Not sure if this is the correct forum for this, but anyways...

My VP2 anemometer is mounted on the east gable of a long, steep, WNW-ESE oriented roof, at only about 3.5' above peak roof level. W, WNW and NW winds are usually recorded on my anemometer as being quite variable, and gusts are often "missed". Wind data from these directions is generally quite poor. I live near the bottom of a steep valley with high tree density, so I used to think that being in the valley or having trees around the yard had more to do with my poor wind obs from certain directions than the roof, but the winds that blow through the yard and hit the house just don't seem to match those on the anemometer when the wind is from W, WNW, or NW. Often, gusts will cause the anemometer to spin around 360 degrees and show lessened wind speeds- for ex; a gust estimated around ~25 mph from the WNW in the trees will be variable and peak at around 15 mph on the anemometer.

So, I was wondering- is my roof the culprit of my poor wind obs from those important directions of W, WNW, and NW? If it's not the roof, it would have to be the terrain (see topo map/anemometer pic below to compare). Winds from perpendicular directions to the roof, such as SW and NE (the front of the house faces due SW, the back due NE) are very consistant with regards to direction and speed, and often seem to give a very "true" representation of wind. The same is true for N winds, which don't have to contend with the spine of the roof. E, SE, and S winds seem to be okay, but almost never occur here, so I don't have a good sampling of data from those directions.

Here is the anemometer in a picture I took facing towards the SW. The roofline goes on to the right of the picture for quite a long distance- it is a very long, steep roof.


Here is a topo map with my location represented by the red dot in the right-center:


I won't be able to change my setup on this house, I'm afraid, but I may be moving in the not-too-distant future. If you guys think the roof is the problem here, I'll make sure to get the anemometer on the potential new house at least ~7' above the roofline.

jwyman

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Re: Anemometer photos- and questions about my setup
« Reply #1 on: March 21, 2008, 01:14:15 PM »
Yep, the ole' roof line induced wind anomaly readings!  #-o

Seriously, get that thing up! ( your anemometer that is...  :oops:)

Try to get it up to 10' above the roof line.... That should take care of most wind eddies...

Here's a phot of my setup...



Jim
« Last Edit: March 21, 2008, 01:16:54 PM by jwyman »

Offline Anthony

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Re: Anemometer photos- and questions about my setup
« Reply #2 on: March 22, 2008, 08:52:33 AM »
If you indeed raise it to 10' and you use PVC. The PVC may not be rigid enough. Might want to consider using metal. But this will require that you ground it. So PVC and some guy wires might be your best option.



Thanks,
Anthony
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Offline NorthNJwx

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Re: Anemometer photos- and questions about my setup
« Reply #3 on: March 22, 2008, 05:51:03 PM »
Thanks for the responses- I'm very glad to know for sure now what my problem is (the roof!).

Since there is a possibility that I'll be moving later this year, I won't be changing anything around with regards to my station setup on the current house. However, I know the lot that I would be moving to (just checked it out for the 3rd or 4th time earlier) and have come to a conclusion- I think the best setup for the potential new house would be to build a 30-40' tower. I've been doing some research, which has led me to the tower idea.

This leads me to another question...say the best place for me to build a tower would be to the east of the new house, maybe 80-100 ft away. If the new house is going to be roughly 30 ft tall w/a steep roof, how high should I get the anemometer on the tower to minimize influence from the house on west winds? I was thinking maybe a 30' tower /6' to 10' mast atop it...getting the anemometer into the 36-40' range. So, would the winds hitting the anemometer be affected by the house if the anemometer is, say, 38' up, the house is 30' tall, and the anemometer is 80 ft horizontally away from the house?

Offline Anthony

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Re: Anemometer photos- and questions about my setup
« Reply #4 on: March 23, 2008, 08:11:46 AM »
Recommended or standard anemometer height is 33'. If the tower is going to be 80' to 100' from the house, it should have no effect what so ever. I think the recommended distance from trees, buildings, etc is 30' to 50'?



Thanks,
Anthony
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Offline NorthNJwx

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Re: Anemometer photos- and questions about my setup
« Reply #5 on: March 23, 2008, 09:33:54 AM »
Recommended or standard anemometer height is 33'. If the tower is going to be 80' to 100' from the house, it should have no effect what so ever. I think the recommended distance from trees, buildings, etc is 30' to 50'?



Sounds great; I actually just reviewed a plan of the house on paper and the distance is going to be more like 50-60' (if the tower does go in that spot), which should still be good. It is far from meeting the CWOP guidelines, but should be good anyway. My only criteria is for the anemometer to be completely free from influence of house eddies that could affect wind direction and speed. I suppose getting it above the house height would largely eliminate that threat anyway, but I'll probably get the anemometer up 40' anyway to really be certain.

I haven't seen many ground-based tower wx stations, but would love to know the results from anyone who has one.

Offline Anthony

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Re: Anemometer photos- and questions about my setup
« Reply #6 on: March 24, 2008, 08:34:47 AM »
I've see a few photos on other forums where people have mounted the anemometer on the tower. And not at the very top either.



Thanks,
Anthony
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Offline NorthNJwx

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Re: Anemometer photos- and questions about my setup
« Reply #7 on: March 24, 2008, 05:24:51 PM »
I've see a few photos on other forums where people have mounted the anemometer on the tower. And not at the very top either.



I've seen some pics of that type of setup, but I'm going to need to put the anemometer on a mast atop the tower due to obstructions. The trees surrounding the site/the house itself are going to warrant getting it up at least 35' or so. So far, the most cost effective solution seems to be a 30', self-supporting tower, w/a 5-10' mast attached to the top of that. Due to the light weight of the anemometer, I don't think even a 10' mast should have any problems with sturdiness. I'll be getting another VP2, so the design of the VP2 anemometer should work in my favor- the arm extending outward from the anemometer itself to the mast is small on the VP2, wheras I know that many other anemometers from other manufacturers have a longer arm. Ah, decisions- this probably won't happen until the fall, so I have plenty of time to figure out the details.