On the Scales of Motion and Internal Stress Characteristics of the Hurricane

Abstract

In cumulus convective atmospheres where important energy and momentum interactions are occurring on the cumulus cloud scale (width 1 to 3 nautical miles) dynamical processes may be significantly different than middle latitude baroclinically driven circulations. This is the case especially in the intense cumulus-convective atmosphere of the hurricane. The purpose of this study is to present recent observational information of the cloud-scale and meso-scale wind fluctuations in the hurricane and to discuss their possible significance with regard to understanding the dynamics of the cumulus convective atmosphere. Detailed investigation is made of the wind observations collected during the 1958 season by the National Hurricane Research Project (NHRP) B-50 aircraft from 28 radial penetrations in hurricanes at levels between 830 and 560 mb. Horizontal wind velocities are measured with the aid of an AN/APN-82 radio navigation instrument utilizing Doppler frequency shift. These measurements, together with the author's (Gray, 1965) previous calculation of vertical air velocity along these same radial legs, give the complete three-dimensional cylindrical wind representation to a space resolution of approximately one-half nautical mile. From the characteristic width of the component fluctuations, space smoothing along the radial legs is performed. With certain approximations this allows determination of the three component space-smoothed (mean) and eddy winds. Computations of the turbulent Reynolds stress from these cloud-scale wind fluctuations are made. Observational evidence of the correlation of cloud-scale horizontal and vertical wind components is presented. Other aspects of the hurricane circulation are discussed.