Abstract
Stability of a one-layer density-driven coastal current with a surface front whose potential vorticity is uniformly zero is examined, and it is shown that such a current can be unstable if the stability condition derived by Paldor (1983) is not satisfied,i.e., the current width,L, is larger than 2/3U/f, wheref is the Coriolis parameter andU is the current velocity at the front. This instability is caused by the coalescence of a frontal trapped and coastal trapped waves. The energetics of this instability and the effect of potential vorticity gradient are also discussed.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Cairns, R.A. (1979): The role of negative energy waves in some instabilities of parallel flows. J. Fluid Mech.,92, 1–14.
Eady, E.T. (1949): Long waves and cyclone waves. Tellus,1, 33–52.
Griffiths, R.W., P.D. Killworth and M.E. Stern (1982): Ageostrophic instability of ocean currents. J. Fluid Mech.,117, 343–377.
Killworth, P. D. (1983): Long-wave instability of an isolated front. Geophys. Astrophys. Fluid Dyn.,25, 235–258.
Killworth, P.D. and M.E. Stern (1982): Instabilities on density driven boundary currents and fronts. Geophys. Astrophys. Fluid Dyn.,22, 1–28.
Killworth, P.D., N. Paldor and M.E. Stern (1984): Wave propagation and growth on a surface front in a two-layer geostrophic current. J. Mar. Res.,42, 761–785.
Kubokawa, A. (1985): Instability of a geostrophic front and its energetics. Geophys. Astrophys. Fluid Dyn.,33, 223–257.
Kubokawa, A. and K. Hanawa (1984): A theory of semigeostrophic gravity waves and its application to the intrusion of a density current along a coast. Part 1. J. Oceanogr. Soc. Japan,40, 247–259.
Legeckis, R. (1978): A survey of worldwide sea surface temperature fronts detected by environmental satellites. J. Geophys. Res.,83, 4501–4522.
Mechoso, C.R. and D.M. Sinton (1983): On the energy analysis of two layer frontal model. J. Atmos. Sci.,40, 2069–2074.
Orlanski, I. (1968): Instability of frontal waves. J. Atmos. Sci.,25, 178–200.
Paldor, N. (1983): Stability and stable modes of coastal fronts. Geophys. Astrophys. Fluid Dyn.,27, 217–228.
Ramp, S.R., R.C. Beardsley and R. Legeckis (1983): An observation of frontal wave development on a shelf-slope/warm core ring front near the shelf break south of New-England. J. Phys. Oceanogr.,13, 907–912.
Stern, M.E. (1980): Geostrophic front, bore, breaking and blocking waves. J. Fluid Mech.,99, 687–703.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Kubokawa, A. Instability caused by the coalescence of two modes of a one-layer coastal current with a surface front. J Oceanogr 42, 373–380 (1986). https://doi.org/10.1007/BF02110432
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF02110432