Surface Convection and the Distribution of Temperature near a Heated Surface

Abstract

LAST summer we took some temperature measurements under the steady conditions prevailing at the epoch of diurnal maximum temperature above an asphalted road where inferior mirage could be seen on any clear day. The temperature variation with height above a hot surface was shortly afterwards measured also in the laboratory. The lapse-rates were of the order of 20°–30° C. per cm. in the first centimetre, and of the order of 1°–2° C. per cm. at higher levels near a heated surface. The observations showed that there was (1) a ‘skin layer’ within the first centimetre, and (2) a ‘surface layer’ extending up to about 20 cm. above the hot surface. The variation of temperature above these layers is practically negligible compared to the much larger variations below.