Seasonal variation of eddy kinetic energy of the North Pacific Subtropical Countercurrent simulated by an eddy‐resolving OGCM

Noh, Yign; Yim, Bo Young; You, Sung Hyup; Yoon, Jong Hwan; Qiu, Bo

doi:10.1029/2006gl029130

Cited by 25 publications

(22 citation statements)

References 21 publications

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“…Also, the large increase in EKE in the FWD experiment, after the change to WRF forcing, is not seen in assimilation experiments, as EKE values maintain a range of 200-300 (cm/s) 2 over the domain and 400-700 (cm/s) 2 in lee during this time period. The EKE levels from assimilation experiments agree well with estimates from eddy-resolving ocean general circulation models [Noh et al, 2007].…”

Section: Impact Of Assimilation On Low-frequency Dynamicssupporting

confidence: 73%

Analysis of four‐dimensional variational state estimation of the Hawaiian waters

Matthews¹,

Powell²,

Janeković³

2012

J. Geophys. Res.

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[1] In this study, we evaluate results from an incremental strong constraint four-dimensional variational data assimilation (IS4D-Var) experiment applied to the circulation around the Hawaiian Islands using the Regional Ocean Modeling System (ROMS). Assimilated observations include (1) satellite-derived high-resolution swath radiometer sea surface temperatures (SST) and along-track altimetric sea surface heights (SSH) and (2) in situ temperature and salinity profiles from Argo floats, autonomous Seagliders, and shipboard conductivity-temperature-depth. Two assimilation configurations are compared: adjusting initial conditions versus adjusting both initial conditions along with atmospheric forcing. In the latter case, we compare two separate forcing products. For all experiments, we investigate how the assimilation alters the tidal, inertial, and mesoscale variability. Significant improvements in the observation-model fit are found for SST and salinity regardless of assimilation configuration or atmospheric forcing; however, significant change to the subsurface temperature is made when adjusting only initial conditions. Baroclinic tides are altered during the assimilation because of changes in the density field in regions of strong internal tide generation. Spurious inertial oscillations are found in assimilation circulations that are associated with the IS4D-Var increment when using either SST or SSH observations; however, this increase in the inertial energy had minimal effect on the mesoscale variability.

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Section: Impact Of Assimilation On Low-frequency Dynamicssupporting

confidence: 73%

Analysis of four‐dimensional variational state estimation of the Hawaiian waters

Matthews¹,

Powell²,

Janeković³

2012

J. Geophys. Res.

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“…The fact that this second enhanced eddy variability band is associated with the North Pacific Subtropical Countercurrent (STCC) has been noted by several recent studies (e.g., Qiu 1999;Roemmich and Gilson 2001;Kobashi and Kawamura 2002;Noh et al 2007). Figure 2 shows the typical latitude-depth section of time-mean temperature and zonal geostrophic velocity in the western North Pacific Ocean.…”

Section: Introductionmentioning

confidence: 86%

Interannual Variability of the North Pacific Subtropical Countercurrent and Its Associated Mesoscale Eddy Field

Qiu

Chen

2010

Journal of Physical Oceanography

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197

158

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Interannual changes in the mesoscale eddy field along the Subtropical Countercurrent (STCC) band of 188-258N in the western North Pacific Ocean are investigated with 16 yr of satellite altimeter data. Enhanced eddy activities were observed in 1996-98 and 2003-08, whereas the eddy activities were below average in 1993-95 and 1999-2002. Analysis of repeat hydrographic data along 1378E reveals that the vertical shear between the surface eastward-flowing STCC and the subsurface westward-flowing North Equatorial Current (NEC) was larger in the eddy-rich years than in the eddy-weak years. By adopting a 2½-layer reduced-gravity model, it is shown that the increased eddy kinetic energy level in 1996-98 and 2003-08 is because of enhanced baroclinic instability resulting from the larger vertical shear in the STCC-NEC's background flow. The cause for the STCC-NEC's interannually varying vertical shear can be sought in the forcing by surface Ekman temperature gradient convergence within the STCC band. Rather than El Niñ o-Southern Oscillation signals as previously hypothesized, interannual changes in this Ekman forcing field, and hence the STCC-NEC's vertical shear, are more related to the negative western Pacific index signals.

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“…Although the NEC is very stable, the vertically sheared NEC‐STCC is baroclinically unstable, this process being more important than its interaction with the Subtropical Front in terms of eddy field generation and seasonal modulation [ Qiu , 1999]. Consequently, its variability generates the second highest eddy kinetic energy regions of the north Pacific [see Qiu , 1999; Noh et al , 2007]. However, the latter studies did not analyze the narrow multiple mean circulation bands of the STCC demonstrated by Hasunuma and Yoshida [1978], who found three separated eastward flows near 19°N, 23°N, and 28°N west of 140°E.…”

Section: North Pacific Ocean Circulationmentioning

confidence: 99%

Mean mesoscale global ocean currents from geodetic pre‐GOCE MDTs with a synthesis of the North Pacific circulation

Vianna¹,

Menezes²

2010

J. Geophys. Res.

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[1] A new milestone in satellite geodesy is about to be completed with the expected availability of the high-resolution data from the already in-orbit Global Ocean Circulation Explorer (GOCE) satellite. There are still some open questions related to capability of recovering mean mesoscale (50 km plus) geostrophic circulation (MGC) patterns from observational Gravity Recovery and Climate Experiment (GRACE)-based geodetic Mean Dynamic Topography (MDTs), which we examine here in detail. A new set of global geodetic MDTs with high grid resolutions was computed (0.1°and 0.25°) based on the newest EGM08 and GRACE GGM02 geoid models. The high resolution coupled to good mesoscale feature discrimination was derived using efficient filtering procedure based on singular spectrum analysis. The new solutions were contrasted with five important MDTs, including the hybrid and the geodetic MDTs, through empirical orthogonal functions analysis, which permit the determination of the mutual correlation among the MDTs, and establishment of error bounds. The methodology made viable a detailed and robust analysis of the North Pacific Ocean circulation based on these MGCs including comparisons with known results from other studies. We prove the superiority of the geodetic EGM08 (as opposed to hybrid) MDT models by obtaining less noisy and more intense and slender western boundary currents and their recirculations, the bifurcations at the Shatsky Rise, and the known mean eddies in the low-latitude shear region (NEC-NECC).Citation: Vianna, M. L., and V. V. Menezes (2010), Mean mesoscale global ocean currents from geodetic pre-GOCE MDTs with a

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Seasonal variation of eddy kinetic energy of the North Pacific Subtropical Countercurrent simulated by an eddy‐resolving OGCM

Cited by 25 publications

References 21 publications

Analysis of four‐dimensional variational state estimation of the Hawaiian waters

Analysis of four‐dimensional variational state estimation of the Hawaiian waters

Interannual Variability of the North Pacific Subtropical Countercurrent and Its Associated Mesoscale Eddy Field

Mean mesoscale global ocean currents from geodetic pre‐GOCE MDTs with a synthesis of the North Pacific circulation

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