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Effects of Ambient Velocity Shear on Nonlinear Internal Wave Associated Mixing at the Columbia River Plume Front

Description: 
Large-amplitude nonlinear internal waves (NLIWs) are frequently observed propagating away from Columbia River tidal plume fronts. They are generated because of the deceleration of the frontal bulge. During the River Influences on Shelf Ecosystems project cruises, the velocity, density structure and acoustic backscatter of the plume fronts and frontal NLIWs were observed using a towed vehicle, vessel-mounted instrumentation, and a vessel X band radar. These observations indicate that in the presence of strong ambient velocity shear, the NLIWs with maximum amplitudes occur well below the density interface and at a depth deeper than in the absence of shear. This deepening of the NLIW shear is associated with intensified vertical mixing below the interface. This is consistent with a dynamic analysis of NLIWs under the influence of sheared ambient flow, obtained from a high-order KdV model. There are two mechanisms responsible for the vertical turbulent mixing intensification. The nonlinear interaction between ambient shear and the NLIWs increases total velocity shear and causes the gradient Richardson number Rig to decrease below a critical value in certain depth ranges. Also, because of the presence of the ambient shear, the maximum NLIW velocity shear occurs at a depth below the density interface where there is less stratification.
Record Format: 
application/pdf
Record Date: 
2008-06-01T07:00:00Z
Publisher: 
PDXScholar
Subject: 
Plumes (Fluid dynamics)
Columbia River (Or. and Wash.) -- Hydrodynamics
Internal waves
Civil and Environmental Engineering
Type: 
text
Raw Url: 
https://pdxscholar.library.pdx.edu/do/oai/?metadataPrefix=&verb=GetRecord&identifier=oai:pdxscholar.library.pdx.edu:cengin_fac-1028
Source: 
Civil and Environmental Engineering Faculty Publications and Presentations
Repository Record Id: 
oai:pdxscholar.library.pdx.edu:cengin_fac-1028
SetSpec: 
publication:communities
publication:mcecs
publication:cengin_fac
publication:cengin
Record Title: 
Effects of Ambient Velocity Shear on Nonlinear Internal Wave Associated Mixing at the Columbia River Plume Front
Identifier: 
https://pdxscholar.library.pdx.edu/cengin_fac/29
https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1028&context=cengin_fac
Author: 
Pan, Jiayi
Jay, David A.
Database: 
Resource OE Format: 
randomness