The Effect of Vertical Wind Shear on Tropical Cyclone Movement
Abstract
A 3-dimensional primitive equation model based upon Ooyama's 3-layer incompressible fluid model is used to investigate tropical cyclone motion. The governing equations are solved on a doubly periodic midlatitude beta-plane using a spectral method with Fourier basis functions. Numerical f-plane simulations are run which successively include a nearly linear horizontal barotropic basic current, surface drag, and cumulus convection. Simulations are then run, under identical conditions, with increasingly greater magnitudes of westerly vertical wind shear. All simulations are repeated using a variable Coriolis parameter to incorporate the beta-effect. Relative vorticity advection had the most dominant effect on tropical cyclone motion followed by the beta-effect. Inclusion of surface drag and cumulus convection also had significant effects. Surface drag retarded vortex speed and resulted in a rightward deviation of the vortex relative to the direction of the basic current. Cumulus convection also resulted in vortex deviations to the right of the tract towards the regions of diabatic heating associated with areas of maximum boundary layer convergence. The primary effect of unidirectional vertical wind shear on cyclone movement, evident in all shear simulations, results in an initial deviation of the simulated cyclone towards the right of the direction of the wind shear vector. A secondary effect, observed in some cases, from vertical vortex tilt due to the differential motion between the upper and lower layer vortices caused by vertically varying winds. Theses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1988
- Accession Number
- ADA197218
Entities
People
- Kim M. Talbert
Organizations
- Air Force Institute of Technology