An Investigation of a Gravity Wave during GALE: 6 February 1986
Abstract
A mesoscale inertia-gravity wave that propagated northeastward across the southeastern United States on 6 February 1986 is investigated. Barograph traces and surface pressure perturbations based on hourly observations were used to trace the wave to its origin in the northwest Gulf of Mexico. The analysis shows that the wave propagated in the direction of the mid- and upper- tropospheric flow for over 19 hours at a mean speed of 25 ms to the minus 1 power. The wave initially expanded as an arc, but the northern edge became bounded by a frontal system. Over the entire event, the half-period ranged from 25 minutes near its origin to 2 hours at the U.S. east coast. The half- wavelength is about 130 km with a crest to trough pressure range of less than 1. 0 up to 5.7 mb along the axis of propagation. Potential source mechanisms for the gravity wave were examined. These included orographic forcing; shear instability; geostrophic adjustment; density impulses and convection. Available evidence leads to the conclusion that intense and explosively growing convection provided the initial energy. After its initiation the gravity wave marked the sharp western edge of a convective line moving eastward along the Gulf Coast. The long-lived horizontal propagation of the gravity wave is shown to be the result of a ducting structure within the mean flow. This structure was revealed by Richardson number and critical level profiles at several sounding stations along the wave path. The duct is eventually disrupted by the frontal structure which marks the northern edge of the gravity wave. Keywords: Theses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1990
- Accession Number
- ADA227655
Entities
People
- Kenneth S. Smith
Organizations
- Air Force Institute of Technology