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Effect of shade on temperature


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Posted
  • Location: Penrith Cumbria
  • Weather Preferences: Cold, snowy winters and warm sunny summers
  • Location: Penrith Cumbria

I have my Nexus Temperature Sensor shielded in a home made screen which works very well even on a sunny summers today, however, this time of year the screen is only in the sun until midday when it goes into shade created by my house situated 15 meters away.

Does this 'unnatural' shade affect the screen temperature? The screen creates it's own shade of course but does having the screen itself in the shade lower temperatures further?

My readings are close to a nearby MetO station on most days but I do worry about this shaded effect.

Andy

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Posted
  • Location: Derbyshire Peak District. 290 mts a.s.l.
  • Weather Preferences: Anything extreme
  • Location: Derbyshire Peak District. 290 mts a.s.l.

I don't think you have anything to worry about. Under the vast majority of atmospheric conditions any 'error' created by the artificial shade from your house would be less than the inherent 'errors' created by  even a Met' Office spec' screen and if your readings are generally quite close to those from the nearest Met' Office site your home made screen must be doing a reasonable job. 

 

The conditions most likely to give false readings are calm, clear days in summer with strong sunshine when even Stevenson Screens have been shown to result in readings up to 1.5c too high ( compared to an aspirated thermistor in free air in the shade) due to absorbtion of solar radiation by the screen itself.  Under these conditions the artificial shade created by your house might actually mitigate the  anomalously high readings which would be created by your screen, resulting in a reading closer to the 'real' temperature than would otherwise have been the case.

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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset

You've answered your own question in some respects. The sensor should be in the shade anyway - it's the temperature of the air that is measured. The air won't be cooler at the back of the house (in the shade) than at the front (in the sun) only the "feel" would be different. :)

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Posted
  • Location: Penrith Cumbria
  • Weather Preferences: Cold, snowy winters and warm sunny summers
  • Location: Penrith Cumbria

Thanks guys that's good to know.

 

Its often said when setting up a weather station that the station should be twice as far from a building as the building is high.

 

This is probably to prevent heating of the instruments during hot whether in summer.

 

Pre Stevenson screen days it was standard practice to place the thermometer on a north facing wall!

 

Andy

Edited by Penrith Snow
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