Accession Number : AD0258549

Title :   A STUDY OF THE PULSATING GROWTH OF CUMULUS CLOUDS

Corporate Author : AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS

Personal Author(s) : ANDERSON,CHARLES E.

Report Date : DEC 1960

Pagination or Media Count : 148

Abstract : The growth of five cumulus congestus clouds over the Santa Catalina Mountains near Tucson, Arizona, was subjected to detailed examination by means of photogrammetric and statistical analysis. These clouds were found to exhibit a pulsating form of cellular convection as they grew upward. Once maximum height was achieved, the circulation became a linearly-increasing function of time. The pulsations were found to be related to the buoyancy-restoring force of the statically stable air with frequencies near 10 minutes. Higher frequencies were found near one to two minutes which could not be definitely accounted for by conventional turbulence theory. An overall acceleration of the motion was shown to be caused by an underlying flow which responded to the mean state of the cloud column. A physical model is proposed for the circulation of a growing cumulus in which two cells are acting concurrently, yet independently, along the same vertical axis. The correct time behavior is shown to result from applying Bjerknes' circulation theorem, modified to include entrainment and mixing. (Author)

Descriptors :   *CONVECTION, *CUMULUS CLOUDS, AERIAL PHOTOGRAPHY, AIR, AIR MASS ANALYSIS, CLOUDS, GROWTH(PHYSIOLOGY), MAPPING, STATISTICAL ANALYSIS, TURBULENCE

Distribution Statement : APPROVED FOR PUBLIC RELEASE