The Transient Gravity Wave Critical Layer.

1984 ◽  
Author(s):  
T. J. Dunkerton
Keyword(s):  
Gravity Wave ◽  
Critical Layer

A theoretical model analysis of the sudden narrow temperature-layer formation observed in the ALOHA-93 Campaign

2002 ◽  
Vol 80 (12) ◽  
pp. 1543-1558 ◽  
Author(s):  
H Hur ◽  
T Y Huang ◽  
Z Zhao ◽  
P Karunanayaka ◽  
T F Tuan
Keyword(s):  
Energy Dissipation ◽  
Gravity Wave ◽  
Temperature Rise ◽  
Critical Level ◽  
Inversion Layer ◽  
Phase Speed ◽  
Temperature Inversion ◽  
Critical Layer ◽  
Mean Flow ◽  
Wind Profiles

The behavior of temperature and wind profiles observed on 21 October 1993 in the ALOHA-93 Campaign is theoretically and numerically analyzed. A sudden temperature rise took place in a very narrow vertical region (3–4 km) at about 87 km. Simultaneously observed radar wind profiles and mesospheric airglow wave structures that show a horizontal phase speed of 35 m/s and a period of about half an hour strongly suggest that a critical level may occur in the proximity of that altitude and that the energy dissipation due to the interaction of the gravity wave with the critical level causes the temperature rise. The numerical model used is a solution to the gravity wave – mean-flow interaction in the critical layer, including a simple cooling mechanism and a wave-energy dissipation simulated by the "optical model" technique. The solutions for the temperature variations so obtained show good agreement with the observed temperature profiles at different times, providing a quantitative explanation for the temperature inversion layer as a phenomenon of gravity wave – critical layer interaction. PACS Nos.: 91.10V, 94.10D

Laboratory Observations of Gravity Wave, Critical Layer Flows Using Single and Double Wave Forcing

1994 ◽  
Vol 47 (6S) ◽  
pp. S113-S117
Author(s):  
Donald P. Delisi ◽  
Timothy J. Dunkerton
Keyword(s):  
Gravity Wave ◽  
Wave Breaking ◽  
Critical Level ◽  
Phase Speed ◽  
Vertical Shear ◽  
Critical Layer ◽  
Small Scale ◽  
Mean Flow ◽  
Wave Forcing ◽  
Internal Mixing

Laboratory measurements of gravity wave, critical layer flows are presented. The measurements are obtained in a salt-stratified annular tank, with a vertical shear profile. Internal gravity waves are generated at the floor of the tank and propagate vertically upward into the fluid. At a depth where the phase speed of the wave equals the mean flow speed, defined as a critical level, the waves break down, under the right forcing conditions, generating small scale turbulence. Two cases are presented. In the first case, the wave forcing is a single, monochromatic wave. In this case, the early wave breaking is characterized as Kelvin-Helmholtz breaking at depths below the critical level. Later wave breaking is characterized by weak overturning in the upper part of the tank and regular, internal mixing regions in the lower part of the tank. In the second case, the wave forcing is two monochromatic waves, each propagating with a different phase speed. In this case, the early wave breaking is again Kelvin-Helmholtz in nature, but later wave breaking is characterized by sustained overturning in the upper part of the tank with internal mixing regions in the lower part of the tank. Mean velocity profiles are obtained both before and during the experiments.

scholarly journals A Physical Interpretation of the Wind-Wave Instability as Interacting Waves

2017 ◽  
Vol 47 (6) ◽  
pp. 1441-1455 ◽  
Author(s):  
J. R. Carpenter ◽  
A. Guha ◽  
E. Heifetz
Keyword(s):  
Gravity Wave ◽  
Physical Interpretation ◽  
Wind Wave ◽  
Wave Interaction ◽  
Flow Speed ◽  
Shear Instability ◽  
Critical Layer ◽  
Surface Gravity ◽  
Wave Instability ◽  
Surface Gravity Wave

AbstractOne mechanism for the growth of ocean surface waves by wind is through a shear instability that was first described by Miles in 1957. A physical interpretation of this wind-wave instability is provided in terms of the interaction of the surface gravity wave with perturbations of vorticity within the critical layer—a near-singularity in the airflow where the background flow speed matches that of the surface gravity wave. This physical interpretation relies on the fact that the vertical velocity field is slowly varying across the critical layer, whereas both the displacement and vorticity fields vary rapidly. Realizing this allows for the construction of a physically intuitive description of the critical layer vorticity perturbations that may be approximated by a simple vortex sheet model, the essence of the wind-wave instability can then be captured through the interaction of the critical layer vorticity with the surface gravity wave. This simple model is then extended to account for vorticity perturbations in the airflow profile outside of the critical layer and is found to lead to an exact description of the linear stability problem that is also computationally efficient. The interpretation allows, in general, for the incorporation of sheared critical layers into the “wave interaction theory” that is commonly used to provide a physical description and rationalization of results in the stability of stratified shear flows.

Evidence of Saturation in a Gravity-Wave Critical Layer

1992 ◽  
Vol 49 (24) ◽  
pp. 2560-2563
Author(s):  
Timothy J. Dunkerton ◽  
Robert E. Robins
Keyword(s):  
Gravity Wave ◽  
Critical Layer

Laboratory Observations of Gravity Wave Critical-Layer Flows

1989 ◽  
pp. 445-461
Author(s):  
Donald P. Delisi ◽  
Timothy J. Dunkerton
Keyword(s):  
Gravity Wave ◽  
Critical Layer

Nonlinear critical-layer evolution of a forced gravity wave packet

2003 ◽  
Vol 493 ◽  
pp. 151-179 ◽  
Author(s):  
L. J. CAMPBELL ◽  
S. A. MASLOWE
Keyword(s):  
Wave Packet ◽  
Gravity Wave ◽  
Critical Layer
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