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Weather station positioning

Archived Nerdy Forum (Weather Q&A).
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nafets
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Weather station positioning

Post by nafets »

Hey guys, I've had my weather station (oregon) for a while now, but i have some issues with the positioning; i.e thermometer overheads, rain gauge under reads. The thermometer is planted on the house, facing north under a verandah. After reading on a few websites, apparently it shouldn't be underneath a metal roof as it acts as a shield to extreme heat and cold, allow air flow to the sensor and keep away from concrete surfaces as most of us know. But all those reasons are hard to avoid; if i move it out of the verandah, its exposed to the sun and rain....i dont know ahaha could someone please tell me where i could relocate it?

With the rain gauge, its sheltered a bit by trees and other obstructions. If i put it on the roof, will it affect readings also?
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daviescr
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Re: Weather station positioning

Post by daviescr »

Hey nafets,
I had the same issue with my old station, thermo/hygro was in the wrong spot and consistently read about 1.5-2c above, more on days >30c. I got a new wireless system early this year and placed the sensor in the most shady spot in the garden - actually never gets direct sunlight, and is well away from the influence of the house. So far found it to be much more accurate, especially when it's been real cold.

for my anemometer I have placed it up a 2 meter pole on the highest point of the roof.

The rain gauge was pretty accurate most of the time, so the new one is in the same spot, on the most northerly point and flattest part of the roof.

basically, keep the temp sensor away from sun and influence from other heat sources (like a house); rain gauge on as flat a surface and as open area as possible (no trees within at least 5 meters); and the anemometer as high as possible away from trees etc as well.

There are plenty of other considerations, but for me, these basics work :) good luck

Chris
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Re: Weather station positioning

Post by nafets »

Thanks for the reply chris,

I think the rain gauge should be easy to move onto the roof, its fairly sheltered ATM. But as you said, the thermo/hydro over reads by about 2c! Is yours exposed to rain? I can locate it into the garden, but i read that the humidity will over read then from transpiration...so hard! SOunds like a good idea though ;)
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apocalypse
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Re: Weather station positioning

Post by apocalypse »

The rain gauge should be fine on the roof, provided it's not obstructed by any trees, etc, to get the most accurate measurments. I've got two - one on the roof and the other on the ground - and they generally read the same.

You may need to build a stevenson screen for the thermometer, because once it is influenced by some form of radiation (whether it be in the shade even) it will read higher than the ambient temperature. Mine is partially exposed to the sun (it's contained inside a small screen) and will often read 6c + in summer, so it has to be well built.
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Re: Weather station positioning

Post by nafets »

The roof should be fine, no trees higher than it! Might be hard to make a stevenson screen, but ill look into it.
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Re: Weather station positioning

Post by Thunder »

Here's a little bit of reading regarding placement of weather instruments from the WMO- http://www.wmo.int/pages/prog/www/IMOP/ ... MetObs.pdf" onclick="window.open(this.href);return false;

I think it's almost impossible in suburbia to get an uncompromised placement, especially on my measly 400 squares! :( In the end I look at it as the instruments are taking readings at a microclimate level and then they are read as Mesoscale+ which makes mounting important but it depends how serious you are. I think this is the most true for the Thermo/Hygro which is easy to comp. over grass or near plants causes DP misreads due to transpiration, solar or thermal radiance over reading temps ect, it really turns into a nightmare quick... personally I run the most compromised setup, my anemometer is ok except it can't handle cloudy days in a row, my rain gauge suffers blocking on its western semi-circle and my thermo is probably the worst example... Mounted on a block rendered wall, under eave, facing north, over height(2m), gets direct sunlight at least twice a day including in the afternoon(worst-but depends on time of year),next to a twin head AC unit for the ducted whole house system and it was over grass but the grass has been replaced by river rock! :grin: The rock has added another +0.7C-0.9C to the temp comp. But it will be exponential come summer!

Solution...

Image

Image

DIY FARS(Fan Aspirated Radiation Sheild), the pipe with the fan carries the sensor, it sits inside the gill screen(pancake stack), the fan runs from the solar panel array pictured during the day(also charges the batteries) and runs from the batteries by night. If I mount it where solar comp is still a noticeable problem I can mitigate by wrapping the mounting pipe in silver duct tape- not gaffer tape but the actual shiny insulation looking stuff!
I work on it between "other" weather technical projects so going is slow, might be ready next year???

Good luck nafets!
You're only as happy as you choose to be....I choose to be miserable! :-)

Rainfall Townsville 2013
Jan-301.6(276.4) Feb-63.6(307.1)
YTD-365.2(1150.9)

Rainfall 2012
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