A diurnal variation of temperature at constant levels in the lower atmosphere was observed at all stations in the Los Angeles basin area. The amplitude of the variation increases with height. This variation has been studied as a diurnal oscillation in the height of isentropic surfaces. The rise and fall of isentropic surfaces may indicate an appreciable diurnal change of vertical motion, but in the higher levels, are at least partly explained by errors in measurement of temperatures by radiosondes. In levels below 4,000 feet msl vertical motion of the right order of magnitude could be caused by the diurnal accumulation and depletion of air as a result of the sea-breeze regime.

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* Present address: c/o Pineapple Research Institute, Honolulu, Hawaii. This article is based on work of the authors while at the AAF Weather Research Station, UCLA, 1945.

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