Surface Cooling, Part V

If you go back and look at Surface Cooling, Part III, you will see that we have improved and abbreviated our explanation of the rapid cooling that occurs in the desert when the sun goes down. It was my father who pointed out a simple mechanism by which this cooling must occur. As we already noted, the sand will cool down quickly when the sun sets. As the day-time convection of air above the desert slows to a halt, it brings cool air down from above, and this air will not be warmed by hot sand as it was during the day. It remains cool, which causes the temperature to drop by ten or twenty degrees.