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Author Topic: Temp anomaly  (Read 1562 times)

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Bashy

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Temp anomaly
« on: September 02, 2016, 07:06:33 AM »
There is a Vue station a couple of miles away from me, that is mounted high up for the wind, i keep asking myself, whos temp data
would be more accurate when the sun is out, the Vue's or mine that's only mounted at about  4ft in a 2x fan assisted shield.

Is there any difference in temp from say 1m to say 9m, if not, then why does the met have a standard height? I believe there is a difference, i.e.
radiated heat from the ground dissipates the higher you go, i believe the met Stevenson screens are about 4ft high'ish? so around body height?
so they would get more radiated heat from the ground than say a Vue mounted at 8 or 9m

I have a point here honest, my temp sensor reads about 1C higher later in the day when the sun is out than the Vue station and the Metar at
Lakenheath, i aint sure how the Metar station is situated but i bet its higher than the standard. The vue is about 2miles as the crown flies and
the Metar is prob about 4 miles, so we aint exactly next door, but, its my station that WU removes from the map cause its over the average in
my area

My sensor is calibrated to a sensor Mick sent me and he calibrated that to one of his that he knows is accurate, i also believe that my shield is working
very well, its very well insulated and the 2 fans are drawing a constant airflow over the sensor. The only issue could be from that lack of airflow in my
garden, 6ft high fencing all round and a bungalow, not a tiny garden though. There is some eddying, i can see it with my e-cig clouds, but i would have
thought that the 2x 4k rpm fans would, oh and i have also made a point of letting the grass grown longer around the sensor area, there is a vast
difference in radiating heat from short grass about 1 inch compared to say 3 inches, when its shorter the grass and ground heats up more than when its longer, i believe the grass part is in the met standard too somewhere..

Am i trying to be too hard, after all its only a personal station?

Offline 4wd

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Re: Temp anomaly
« Reply #1 on: September 02, 2016, 07:38:00 AM »
In a well mixed airflow e.g. open site and breezy day it won't be that different.
On still, cold nights the higher location could be significantly warmer and might catch more breeze.
A sheltered plot like most gardens is designed to be warmer for the plants or sitting outside.

In short the problems are complex and probably all but insurmountable unless you have a large open area.
Even the official sites are often compromised to some extent.
As your records build up the comparisons *at that location* are the important thing,

Bashy

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Re: Temp anomaly
« Reply #2 on: September 02, 2016, 10:43:33 AM »
Yeah I can understand that, so, would you say the Vue has the better position to be more accurate then?  I do strive to get the sensors as accurate as I can but as ya say, sometimes ya can only do so much....

Offline NorCal Dan

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Re: Temp anomaly
« Reply #3 on: September 02, 2016, 10:14:36 PM »
The VP2 is the better choice since the anemometer can be mounted up high while leaving the rain bucket and temp sensor down low.  With the all-in-one nature of the Vue it's not possible.

Personally speaking, my station is not NIST calibrated, and honestly, the +/- values for all sensors are extremely wide.  We do the best we can, but let's face it, we are just hobby stations.  We share our data with the big boys...we puff our chests and pretend our data is "dead-nutz balls-on accurate"...but in the big scheme of things our data will never carry the same weight as the official stations.  Not that there's anything wrong with that...just trying to keep things real.

I applaud your efforts to get the best data possible...but in the end we all have to make allowances for not-so-perfect mounting locations for our sensors. 

 

cumulus