A bit late in the day but I was struck over the last few days with the way in which the frost lingered all day on the steeper parts of my north facing hillside despite dawn to dusk sunshine. House and transverse walls all had a permanent frost shadow which was only to be expected but so did some of the steeper open ground that would at least have been getting some sunshine, albeit at an extreme incidence angle.
Not sure if you are asking a question? but here goes.
This is not surprising, if you think about it, a flat surface set at right angles to the sun will receive the maximum amount of energy and the same surface turned through 90deg will present it's edge to the sun and theoretically will receive no energy. The flat surface set at angles between the two examples above, follow Lambert's cosine law which states that "The radiation received on a flat surface decreases as the angle between the surface and the perpendicular decreases." Therefore the energy received by a flat surface will be the energy received at 90deg multiplied by the cosine of the angle. E(90deg) x cos(angle) = E
Sorry it's a bit garbled, memory not good (Old age and good wine :-)
Regards Don
The message from "Donwill" contains these words:
Actually I wasn't, just making an observation on the disadvantages of living on the north side of a hill.
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