Calculations of Cumulus Vertical Draft Velocities in Hurricanes from Aircraft Observations

Abstract

Abstract In cumulus convective atmospheres the most significant length scale of vertical motion is of cumulus draft size—of horizontal lengths two to four orders of magnitude less than the synoptic scale and of magnitude one to three orders greater. This draft motion on scales between the gust and synoptic motion has been least investigated. The purpose of this paper is to propose a new method of calculating draft velocities from aircraft and present results of calculations with this method in hurricanes. An aircraft Doppler radio navigation instrument which is capable of measuring horizontal wind variations to a space resolution of a fraction of a nautical mile can be employed with other instruments to measure an aircraft's pitch angle changes. From this determination, along with other standard aircraft measurements such as radar and pressure altitude, power setting, etc., it is possible to make determinations of average vertical air motion to space resolutions of 0.4 to 0.7 nautical miles. Calculations ...