Localized multiscale energy and vorticity analysis

Liang, X. San; Robinson, Allan R.

doi:10.1016/j.dynatmoce.2004.12.004

Cited by 62 publications

(59 citation statements)

References 11 publications

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“…For detail theory and derivation of MS-EVA, please refer to Liang and Robinson (2005a) included in this appendix. In the MS-EVA, processes are represented on scale windows.…”

Section: A Brief Description Of Ms-eva Methodsmentioning

confidence: 99%

“…For theory and detailed derivation of MS-EVA, please refer to Liang and Robinson (2005a) and LR05. A brief description of MS-EVA in a symbolic form and the definition of all terms in the equations are included in the appendix.…”

Section: B Analysis With Ms-eva For Case IVmentioning

confidence: 99%

“…Through exploring pattern generation and energy transfers, transports, and conversions, the intricate relationships between events on varying scales and locations in phase space and physical space can be sorted out. The basic idea for this has been delineated and the formulation developed, by Liang and Robinson (2005a), and an avenue to application is established in LR05. The latter study also established a generalization of the concept of stability on a localized basis, which allows one to build an easy-to-use criterion for the identification of baroclinic and barotropic instability processes utilizing actual or modeled ocean and atmosphere datasets.…”

Section: B Analysis With Ms-eva For Case IVmentioning

confidence: 99%

“…This method was used for analyzing the energetics of the Florida Current (Brooks and Niiler 1977) and Gulf Stream after it has passed Cape Hatteras (Rossby 1987). The second method is based on a Multiscale Energy and Vorticity Analysis (MS-EVA) (Liang andRobinson 2005a, 2005b, manuscript submitted to Dyn. Atmos.…”

Section: Diagnostics Of Energy Conversionmentioning

confidence: 99%

“…The multiscale energy and vorticity analysis is a new methodology for the investigation of multiscale interactive oceanic processes that are intermittent in space and time (Liang and Robinson 2005a;LR05). Through exploring pattern generation and energy transfers, transports, and conversions, the intricate relationships between events on varying scales and locations in phase space and physical space can be sorted out.…”

Section: B Analysis With Ms-eva For Case IVmentioning

confidence: 99%

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Effect of Bathymetric Curvature on Gulf Stream Instability in the Vicinity of the Charleston Bump

Xie

Liu

Pietrafesa

2007

Journal of Physical Oceanography

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The effect of the isobathic curvature on the development and evolution of Gulf Stream frontal waves (meanders and eddies) in the vicinity of the Charleston Bump (a topographic rise on the upper slope off Charleston, South Carolina; referred to as CB hereinafter) is studied using the Hybrid-Coordinate Ocean Model (HYCOM). Baroclinic and barotropic energy transfers from the Gulf Stream to its meanders and eddies that appear as cold and warm anomalies are computed for four different cases. In case I, the curvature of the isobaths is artificially reduced and the CB is removed from the bathymetry. In this simulation, the simulated Gulf Stream meanders were barely noticeable in the study region. Energy transfer from the Gulf Stream to meanders and eddies was negligible. In case II, the curvature of the isobaths was the same as in case I, but a bump of the scale of the CB was added to the bathymetry. In this simulation, Gulf Stream meanders were amplified while passing over the CB. In case III, the CB was removed from the bathymetry as in case I, but the curvature of the isobaths was similar to the actual bathymetry, which was larger than that of cases I and II. In this simulation, large meanders were simulated, but the development of these meanders was not confined to the region of the CB. The total baroclinic and barotropic energy transfer rate in this case was an order of magnitude greater than in case II, suggesting that isobathic curvature was able to generate Gulf Stream meanders and eddies even without the presence of the CB. In case IV, actual bathymetry data, which contain both the CB and the isobathic curvature, were used. In this case, large-amplitude Gulf Stream meanders were simulated and there was also a tendency for the amplification of the meanders to be anchored downstream of the CB, consistent with observations. The results from this study suggest that the formation of the "Charleston Trough," a Gulf Stream meander that appears as a low pressure or depressed water surface region downstream of the bump, is the result of the combined effect of the CB and the isobathic curvature in the region. The isobathic curvature plays a major role in enhancing the baroclinic and barotropic energy transfer rates, whereas the bump provided a localized mechanism to maximize the energy transfer rate downstream of the CB.

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“…For detail theory and derivation of MS-EVA, please refer to Liang and Robinson (2005a) included in this appendix. In the MS-EVA, processes are represented on scale windows.…”

Section: A Brief Description Of Ms-eva Methodsmentioning

confidence: 99%

Section: B Analysis With Ms-eva For Case IVmentioning

confidence: 99%

Section: B Analysis With Ms-eva For Case IVmentioning

confidence: 99%

Section: Diagnostics Of Energy Conversionmentioning

confidence: 99%

Section: B Analysis With Ms-eva For Case IVmentioning

confidence: 99%

See 3 more Smart Citations

Effect of Bathymetric Curvature on Gulf Stream Instability in the Vicinity of the Charleston Bump

Xie

Liu

Pietrafesa

2007

Journal of Physical Oceanography

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Nonlinear multiscale interactions and internal dynamics underlying a typical eddy-shedding event at Luzon Strait

Zhao

Liang

Gan

2016

J. Geophys. Res. Oceans

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Eddy‐shedding is a highly nonlinear process that presents a major challenge in geophysical fluid dynamics. Using the newly developed localized multiscale energy and vorticity analysis (MS‐EVA), this study investigates an observed typical warm eddy‐shedding event as the Kuroshio passes the Luzon Strait, in order to gain insight into the underlying internal dynamics. Through multiscale window transform (MWT), it is found that the loop‐form Kuroshio intrusion into the South China Sea (SCS) is not a transient feature, but a quasi‐equilibrium state of the system. A mesoscale reconstruction reveals that the eddy does not have its origin at the intrusion path, but comes from the Northwest Pacific. It propagates westward, preceded by a cyclonic (cold) eddy, through the Kuroshio into the SCS. As the eddy pair runs across the main current, the cold one weakens and the warm one intensifies through a mixed instability. In its development, another cold eddy is generated to its southeast, which also experiences a mixed instability. It develops rapidly and cuts the warm eddy off the stream. Both the warm and cold eddies then propagate westward in the form of a Rossby wave (first baroclinic mode). As the eddies approach the Dongsha Islands, they experience another baroclinic instability, accompanied by a sudden accumulation of eddy available potential energy. This part of potential energy is converted to eddy kinetic energy through buoyancy conversion, and is afterward transferred back to the large‐scale field through inverse cascading, greatly reducing the intensity of the eddy and eventually leading to its demise.

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Absolute and convective instabilities and their roles in the forecasting of large frontal meanderings

Liang

Robinson

2013

J. Geophys. Res. Oceans

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[1] Frontal meanderings are generally difficult to predict. In this study, we demonstrate through an exercise with the Iceland-Faeroe Front (IFF) that satisfactory predictions may be achieved with the aid of hydrodynamic instability analysis. As discovered earlier on, underlying the IFF meandering is a convective instability in the western boundary region followed by an absolute instability in the interior; correspondingly the disturbance growth reveals a switch of pattern from spatial amplification to temporal amplification. To successfully forecast the meandering, the two instability processes must be faithfully reproduced. This sets stringent constraints for the tunable model parameters, e.g., boundary relaxation, temporal relaxation, eddy diffusivity, etc. By analyzing the instability dispersion properties, these parameters can be rather accurately set and their respective ranges of sensitivity estimated. It is shown that too much relaxation inhibits the front from varying; on the other hand, too little relaxation may have the model completely skip the spatial growth phase, leading to a meandering way more upstream along the front. Generally speaking, dissipation/diffusion tends to stabilize the simulation, but unrealistically large dissipation/diffusion could trigger a spurious absolute instability, and hence a premature meandering intrusion. The belief that taking in more data will improve the forecast does not need to be true; it depends on whether the model setup admits the two instabilities. This study may help relieve modelers from the laborious and tedious work of parameter tuning; it also provides us criteria to distinguish a physically relevant forecast from numerical artifacts.Citation: Liang, X. S., and A. R. Robinson (2013), Absolute and convective instabilities and their roles in the forecasting of large frontal meanderings,

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Localized multiscale energy and vorticity analysis

Cited by 62 publications

References 11 publications

Effect of Bathymetric Curvature on Gulf Stream Instability in the Vicinity of the Charleston Bump

Effect of Bathymetric Curvature on Gulf Stream Instability in the Vicinity of the Charleston Bump

Nonlinear multiscale interactions and internal dynamics underlying a typical eddy-shedding event at Luzon Strait

Absolute and convective instabilities and their roles in the forecasting of large frontal meanderings

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