Katabatic winds and the prevention of frost damage

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Abstract
A new instrument for recording air movements of low velocity and air temperature fluctuations, and a portable anti‐radiation screen, suitable for a grass minimum thermometer, are described.Experiments are described showing that certain conditions must be fulfilled in making a just comparison between the air temperature in an orchard‐heated plantation and in an unheated plantation.Observations of air currents on hillsides on radiation nights are presented, which show that two winds exist, the “hilltop” wind and the katabatic wind. The effect of each on the other in certain localities is described. It is shown that the hilltop wind is able, on the higher part of a slope facing it, to push uphill the air in the first 10 ft. or so above the ground, and at a lower level to neutralise the force of the katabatic wind, producing a calm belt on the slope.Experiments designed to demonstrate the magnitude of air temperature differences caused by differences in the vegetative cover of the soil alone, by differences in altitude alone, and by a third unknown factor, are described.Evidence is presented showing that when a katabatic wind moves down a slope its temperature does not necessarily decrease.It is indicated how the new information may be applied to the problem of preventing frost damage to crops.

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