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Originally Posted by mntlblok
Was surprised to find some little patches of frost on the lawn early this morning. Did a bit of googling and was even more surprised to learn that, with the right set of conditions, ground temperature can be as much as 10 degrees cooler than the temperature five or so feet above the ground - the height at which temps are reported. What Causes Frost?. |
The description of radiational cooling in the link is not strictly accurate. It is not radiation into the air or atmosphere. Radiational cooling is radiation (black body radiation) not getting reflected back down. So it escapes the earth's atmosphere as radiation. Cloud cover, or an overhanging tree, prevent or reduce this. The tree will even be radiating toward the ground, which is why you often have frost on a lawn except under trees.
"Clouds in a Glass of Beer: Simple Experiments in Atmospheric Physics" is a nice little book that explains this, as well as other interesting things like why mountains in the distant look more grayish or blue. It is sort of a college text in atmospheric physics for art majors, so it is pretty approachable.