• Carr, L. E., 1989: Barotropic vortex adjustment to asymmetric forcing with application to tropical cyclone motion. Ph.D. dissertation, Naval Postgraduate School, 143 pp. [Available from Dept. of Meteorology, Naval Postgraduate School, Monterey, CA 93940.].

  • ——, and R. T. Williams, 1989: Barotropic vortex stability to perturbations from axisymmetry. J. Atmos. Sci.,46, 3177–3196.

  • ——, and R. L. Elsberry, 1990: Observational evidence for predictions of tropical cyclone propagation relative to environmental steering. J. Atmos. Sci.,47, 542–546.

  • DeMaria, M., 1985: Tropical cyclone motion in a nondivergent barotropic model. Mon. Wea. Rev.,113, 1199–1209.

  • Elsberry, R. L., 1987: Tropical cyclone motion. A Global View of Tropical Cyclone Motions, R. L. Elsberry, W. M. Frank, G. J. Holland, J. D. Jarrell, and R. L. Southern, Eds., Office of Naval Research, 185 pp.

  • Fiorino, M., and R. L. Elsberry, 1989: Some aspects of vortex structure related to tropical cyclone motion. J. Atmos. Sci.,46, 975–990.

  • Holland, G. J., 1984: Tropical cyclone motion: A comparison of theory and observations. J. Atmos. Sci.,41, 68–75.

  • Li, X., and B. Wang, 1994: Barotropic dynamics of the beta gyres and beta drift. J. Atmos. Sci.,51, 746–756.

  • ——, and ——, 1996: Acceleration of hurricane beta drift by the shear train rate of environmental flows. J. Atmos. Sci.,53, 327–334.

  • Smith, R. K., 1991: An analytic theory of tropical-cyclone motion in a barotropic shear flow. Quart. J. Roy. Meteor. Soc.,117, 685–714.

  • ——, X. Li, and B. Wang, 1997: A hurricane beta drift law including meridional shear. Tellus, in press.

  • Ulrich, W., and R. K. Smith, 1991: A numerical study of tropical cyclone motion using a barotropic model. II: Motion in spatially-varying large-scale flows. Quart. J. Roy. Meteor. Soc.,117, 107–124.

  • Wang, B., and X. Li, 1992: The beta drift of three-dimensional vortices: A numerical study. Mon. Wea. Rev.,120, 579–593.

  • ——, and ——, 1995: Propagation of a tropical cyclone in meridional-varying zonal flow: An energetics analysis. J. Atmos. Sci.,52, 1421–1433.

  • Williams, R. T., and J. C.-L. Chan, 1994: Numerical studies of the beta effect in tropical cyclone motion. Part II: Zonal mean flows. J. Atmos. Sci.,51, 1065–1076.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 128 128 7
PDF Downloads 29 29 5

Direction of Hurricane Beta Drift in Horizontally Sheared Flows

View More View Less
  • 1 Department of Meteorology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii
© Get Permissions
Restricted access

Abstract

The impacts of linear environmental shears on beta drift direction are assessed through numerical experiments with a single-layer, primitive equation model. It is found that cyclonic (anticyclonic) shears turn the beta drift more westward (northward) in the Northern Hemisphere. In addition, the longitudinal shear of meridional flows (∂V/∂x) is much more effective than the meridional shear of zonal flows (∂U/∂y) in deflection of the beta drift.

A theoretical model, the beta gyre dynamic system, describing evolution of the beta gyre amplitude and phase angle is advanced to interpret the numerical model results. In this model, the nonlinear energy transfer from the beta gyres to the primary vortex and higher asymmetric modes was partially parameterized by linear damping. The semi-empirical theory predicts that 1) beta drift direction is independent of the planetary vorticity gradient; 2) in a quiescent environment, the drift angle is primarily determined by the outer azimuthal flows of the vortex; and 3) in a sheared environmental flow, the deflection of beta drift induced by environmental shears depends mainly on the longitudinal shear of meridional flows. The authors show that the environmental shear changes beta drift angle by advection of beta gyre vorticity and planetary vorticity, which affects beta gyre orientation.

* Current affiliation: Laboratory for Atmosphere, NASA/Goddard Space Flight Center, Greenbelt, Maryland.

Corresponding author address: Dr. Bin Wang, Department of Meteorology, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822.

Email: bwang@soest.hawaii.edu

Abstract

The impacts of linear environmental shears on beta drift direction are assessed through numerical experiments with a single-layer, primitive equation model. It is found that cyclonic (anticyclonic) shears turn the beta drift more westward (northward) in the Northern Hemisphere. In addition, the longitudinal shear of meridional flows (∂V/∂x) is much more effective than the meridional shear of zonal flows (∂U/∂y) in deflection of the beta drift.

A theoretical model, the beta gyre dynamic system, describing evolution of the beta gyre amplitude and phase angle is advanced to interpret the numerical model results. In this model, the nonlinear energy transfer from the beta gyres to the primary vortex and higher asymmetric modes was partially parameterized by linear damping. The semi-empirical theory predicts that 1) beta drift direction is independent of the planetary vorticity gradient; 2) in a quiescent environment, the drift angle is primarily determined by the outer azimuthal flows of the vortex; and 3) in a sheared environmental flow, the deflection of beta drift induced by environmental shears depends mainly on the longitudinal shear of meridional flows. The authors show that the environmental shear changes beta drift angle by advection of beta gyre vorticity and planetary vorticity, which affects beta gyre orientation.

* Current affiliation: Laboratory for Atmosphere, NASA/Goddard Space Flight Center, Greenbelt, Maryland.

Corresponding author address: Dr. Bin Wang, Department of Meteorology, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822.

Email: bwang@soest.hawaii.edu

Save