Objective Analysis of Aircraft Data in Tropical Cyclones

Abstract

A method for objective analysis of aircraft observations in tropical cyclones has been developed. Quasi-horizontal fields of motion, temperatures, mixing ratios, and D-values are analyzed using a modified version of the method of successive corrections. The weighting functions are specified so that the high degree of circular symmetry characteristic of tropical cyclones is incorporated in the analyses. The analyses are performed on a 25 by 25 Cartesian grid of 5 n mi spacing which is centered on the storm. A special feature is the analysis of vertical motions as determined from aircraft flight characteristics. Three Atlantic storms are analyzed in detail: Hurricanes Inez (1966), Debbie (1969), and Ginger (1971). The analyses show the significant larger-scale features and major asymmetries of these storms. Both Inez and Debbie, which were well organized hurricanes, display characteristic vertical motion patterns in which a ring of strong ascent is found immediately surrounding the eye, with marked descent just outside of the annulus of strong ascent. Maximum ascent and descent rates were each indicated to be a few meters per second in these storms. Ginger was a marginal hurricane with poorly organized eye structure and relatively weak and disorganized patterns of vertical motion.