The Effects of Shear Flow on Propagation of Rossby Waves in the Equatorial Oceans

Zheng, Quanan; Yan, Xiao-Hai; Ho, Chung-Ru; Tai, Chang‐Kou

doi:10.1175/1520-0485(1994)024<1680:teosfo>2.0.co;2

Cited by 20 publications

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“…The slower westward phase speeds in the presence of equatorially asymmetric background shear had previously been documented from eigensolutions for an idealized mean ECS by Chang and Philander (1989) and Zheng et al (1994). The effects of the background shear on the latitudinal structure of the eigenfunctions were not considered in these earlier studies.…”

mentioning

confidence: 95%

The Effects of Wind Forcing and Background Mean Currents on the Latitudinal Structure of Equatorial Rossby Waves

Perez

Chelton

Miller

2005

Journal of Physical Oceanography

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The latitudinal structure of annual equatorial Rossby waves in the tropical Pacific Ocean based on sea surface height (SSH) and thermocline depth observations is equatorially asymmetric, which differs from the structure of the linear waves of classical theory that are often presumed to dominate the variability. The nature of this asymmetry is such that the northern SSH maximum (along 5.5°N) is roughly 2 times that of the southern maximum (along 6.5°S). In addition, the observed westward phase speeds are roughly 0.5 times the predicted speed of 90 cm s Ϫ1 and are also asymmetric with the northern phase speeds, about 25% faster than the southern phase speeds. One hypothesized mechanism for the observed annual equatorial Rossby wave amplitude asymmetry is modification of the meridional structure by the asymmetric meridional shears associated with the equatorial current system. Another hypothesis is the asymmetry of the annually varying wind forcing, which is stronger north of the equator. A reduced-gravity, nonlinear, ␤-plane model with rectangular basin geometry forced by idealized Quick Scatterometer (QuikSCAT) wind stress is used to test these two mechanisms. The model with an asymmetric background mean current system perturbed with symmetric annually varying winds consistently produces asymmetric Rossby waves with a northern maximum (4.7°N) that is 1.6 times the southern maximum (5.2°S) and westward phase speeds of approximately 53 Ϯ 13 cm s Ϫ1 along both latitudes. Simulations with a symmetric background mean current system perturbed by asymmetric annually varying winds fail to produce the observed Rossby wave structure unless the perturbation winds become strong enough for nonlinear interactions to produce asymmetry in the background mean current system. The observed latitudinal asymmetry of the phase speed is found to be critically dependent on the inclusion of realistic coastline boundaries.

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confidence: 95%

The Effects of Wind Forcing and Background Mean Currents on the Latitudinal Structure of Equatorial Rossby Waves

Perez

Chelton

Miller

2005

Journal of Physical Oceanography

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“…The maximum SLA generated by the cyclonic eddy is about 0.1 m and does not show up clearly in the ADT map (Figure c). As pointed out by Zheng et al (), this eddy may be generated from the shear waves of the Kuroshio (Yuan & Zheng, ; Zheng & Yuan, ). The VADCP‐measured currents at 13‐m depth are toward the right (left) side of the currents at 29 m depth in Transect A (B), while the currents at 13‐ and 29‐m depths are basically toward the same direction in Transect C. The VADCP‐measured currents at 29‐m depth are more or less tangent to the ADT isoclines, indicating that the eddy has little effect on the currents at 29‐m depth.…”

Section: Resultsmentioning

confidence: 93%

Effect of a Mesoscale Eddy on Surface Turbulence at the Kuroshio Front in the East China Sea

et al. 2019

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Field observations were conducted along three west‐east transects in the East China Sea Kuroshio Front in July 2017. The microstructure observations results show that the surface turbulence kinetic energy (TKE) dissipation rates in the northern and southern transects are about 2 orders larger than those in the middle transect. The sea surface temperature, mixed layer depth, and the submesoscale motions (with horizontal scales smaller than 30 km) also suggest the surface turbulences are more active in the northern and southern transects. The current velocity data and sea level anomaly show that the middle transect was located at the northern edge of a cyclonic eddy. The eddy‐generated cross‐front geostrophic current was observed to flow toward the opposite direction of the cross‐front Ekman transport and believed to counteract the Ekman buoyancy flux (EBF)‐induced turbulence enhancement. The TKE dissipation rates can be well scaled by a scaling considering the EBF and the wind in the northern and southern transects but wind scaling only in the middle transect, suggesting the EBF does not contribute to the surface turbulence in the middle transect. An improved empirical scaling considering the cross‐front geostrophic current is defined and can scale the TKE dissipation rates better, indicating an eddy plays a key role in surface turbulent mixing in the East China Sea Kuroshio front.

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“…It is exactly in this sense that IFD provides an alternative framework. Some of the previous reports include analysis on the data from various channels, e.g., the laboratory data from mechanically generated waves, 30 whose frequency will down shift as they propagate and thus exhibit non-stationary feature; 9,38,53 field data of waves collected by the National Oceanic and Atmospheric Administration (NOAA); 33 satellite altimetry data for large scale ocean circulation studies; 48,56,84,85 the non-stationary earthquake data; 1,27,49 and laboratory wind data. 32 In all the previous studies, the EMD has been compared with Fourier and other methods to illustrate the associated Hilbert spectral analysis.…”

Section: Applicationsmentioning

confidence: 99%

Iterative Filtering Decomposition Based on Local Spectral Evolution Kernel

2011

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The synthesizing information, achieving understanding, and deriving insight from increasingly massive, time-varying, noisy and possibly conflicting data sets are some of most challenging tasks in the present information age. Traditional technologies, such as Fourier transform and wavelet multi-resolution analysis, are inadequate to handle all of the above-mentioned tasks. The empirical model decomposition (EMD) has emerged as a new powerful tool for resolving many challenging problems in data processing and analysis. Recently, an iterative filtering decomposition (IFD) has been introduced to address the stability and efficiency problems of the EMD. Another data analysis technique is the local spectral evolution kernel (LSEK), which provides a near prefect low pass filter with desirable time-frequency localizations. The present work utilizes the LSEK to further stabilize the IFD, and offers an efficient, flexible and robust scheme for information extraction, complexity reduction, and signal and image understanding. The performance of the present LSEK based IFD is intensively validated over a wide range of data processing tasks, including mode decomposition, analysis of time-varying data, information extraction from nonlinear dynamic systems, etc. The utility, robustness and usefulness of the proposed LESK based IFD are demonstrated via a large number of applications, such as the analysis of stock market data, the decomposition of ocean wave magnitudes, the understanding of physiologic signals and information recovery from noisy images. The performance of the proposed method is compared with that of existing methods in the literature. Our results indicate that the LSEK based IFD improves both the efficiency and the stability of conventional EMD algorithms.

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The Effects of Shear Flow on Propagation of Rossby Waves in the Equatorial Oceans

Cited by 20 publications

References 0 publications

The Effects of Wind Forcing and Background Mean Currents on the Latitudinal Structure of Equatorial Rossby Waves

The Effects of Wind Forcing and Background Mean Currents on the Latitudinal Structure of Equatorial Rossby Waves

Effect of a Mesoscale Eddy on Surface Turbulence at the Kuroshio Front in the East China Sea

Iterative Filtering Decomposition Based on Local Spectral Evolution Kernel

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