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I have see this morning this curious garden where one part was covered with frost while the other was frost free. enter image description here

Question 1: What are the factor that play a role in this configuration?

My guess is radiation from the building and the wind (the frost free part being more protected from the wind by the building) but then I wonder : Will there still be these two zones after a night without any wind? (Question 2)

The left house is heated, the middle one isn't but it's inhabited, the shed is closed but not insulated and without heating source inside. There isn't any other surrounding structures that could create shade.

The open side of the garden is facing south.

I observed the frost after sunrise, but before the sun rays were reaching the garden.

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I would say the most relevant factor involved would be Radiative cooling, with ground areas closer to the buildings not losing as much heat energy as the buildings act to reflect some of the radiation back keeping those areas frost free, while open exposed areas lose more energy and experience frost.

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  • $\begingroup$ Thanks @Siv! Your answer seems to imply that onlythe reflect of the heat from earth on the building back to earth has an effect whereas the link in wikipedia also implies that the temperature of the paper (which is at 300K in their example) also plays a role. So does the temperature of the walls of the building also play a role in radiative cooling? $\endgroup$ – MagTun Jan 16 '16 at 17:44
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    $\begingroup$ @Arone I don't think the paper has enough thermal mass to make much difference. The temperature of the walls will also make a difference to the pattern you observed, though this would be another variable in the formation of the frost, and would be unrelated to the effects of radiative cooling, which I suspect is the main component to the frost pattern you observed, and would relate to some of the other comments to your original question. $\endgroup$ – Siv Jan 16 '16 at 20:05

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