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1 JANUARY 1998 19A F A N A S Y E V A N D P E L T I E R 1998 American Meteorological Society
 

Summary: 1 JANUARY 1998 19A F A N A S Y E V A N D P E L T I E R
1998 American Meteorological Society
The Three-Dimensionalization of Stratified Flow over Two-Dimensional Topography
YA. D. AFANASYEV AND W. R. PELTIER
Department of Physics, University of Toronto, Toronto, Ontario, Canada
(Manuscript received 22 November 1996, in final form 15 April 1997)
ABSTRACT
The authors present a series of new analyses of the problem of stratified flow over a localized two-dimensional
obstacle, focusing upon the detailed dynamical characteristics of the flows that develop when the Froude number
is such that the forced internal waves ``break'' above their topographic source. Results demonstrate that when
the flow is restricted to evolve in two space dimensions, then the intensity of the Kelvin­Helmholtz-like (K­
H) perturbations that form in the downstream shear layer that separates the accelerated low-level jet in the lee
of the obstacle and the overlying region of decelerated flow increases dramatically with the governing parameter
NU/g (U and N are, respectively, the velocity and buoyancy frequency characteristic of the upstream incident
flow, while g is the gravitational acceleration). This nondimensional parameter represents the ratio of the ac-
celeration that a fluid particle feels in the wave to the gravitational acceleration and measures the importance
of non-Boussinesq effects. A marked change in the global characteristics of the flow is shown to occur with
increasing NU/g, characteristics that include the speed of downstream propagation of the so-called chinook front,
the drag exerted by the flow on the obstacle, and the intensity of the K­H instability induced pulsations of the
surface velocity field. When the flow is allowed to access the third spatial dimension, the authors demonstrate

  

Source: Afanassiev, Iakov - Department of Physics and Physical Oceanography, Memorial University of Newfoundland

 

Collections: Geosciences