THE DYNAMICS OF THE RAMDAS LAYER

A little more than sixty years ago, the late L. A. Ramdas discovered a curious atmospheric phenomenon which had not been satisfactorily expl ained till recently. The phenomenon is the observation of a temperatur e minimum some 20-50 cm above bare soil on calm, clear nights. The fir st reports of these observations were treated with much scepticism, as the prevailing view was that the nocturnal temperature minimum always occurs at ground. In the present address the history of work on the l ifted temperature minimum is traced and a new explanation is offered. It is emphasized that in this as well as many other phenomena, it is i mportant to account for surfaces that are not perfectly black radiativ ely, i.e. those whose emissivity is not unity.