Seasonal variability of subthermocline eddy kinetic energy east of the Philippines

AbstractSeasonal modulation of subthermocline Eddy Kinetic Energy (EKE) east of the Philippines and its associated dynamics are studied, using mooring measurements and outputs from an eddy-resolving ocean general circulation model for the period from 2000 to 2017. Significantly high EKE appears below the thermocline in the latitude band between 5°N and 14°N east of the Philippines. Separated by 10°N, the EKE in the northern and southern parts of the region shows nearly opposite seasonal cycles, with its magnitude reaching maximum in early spring and minimum in summer in the northern part and reaching maximum in summer and minimum in winter in the southern part of the region. Further investigation indicates that both baroclinic and barotropic instabilities are essential in generating the subthermocline eddies, but the seasonal variation of subthermocline EKE is mainly caused by the seasonal modulation of barotropic instability. The seasonal modulation of barotropic instability in the northern and southern part of the region is associated with the seasonal evolution of North Equatorial Undercurrent and Halmahera Eddy, respectively.

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Energy of Midlatitude Transient Eddies in Idealized Simulations of Changed Climates

Journal of Climate ◽

10.1175/2008jcli2099.1 ◽

2008 ◽

Vol 21 (22) ◽

pp. 5797-5806 ◽

Cited By ~ 72

Author(s):

Paul A. O’Gorman ◽

Tapio Schneider

Keyword(s):

Kinetic Energy ◽

Potential Energy ◽

Radiative Forcing ◽

General Circulation ◽

Thermal Structure ◽

Circulation Model ◽

Static Stability ◽

Eddy Kinetic Energy ◽

Available Potential Energy ◽

Wide Range

Abstract As the climate changes, changes in static stability, meridional temperature gradients, and availability of moisture for latent heat release may exert competing effects on the energy of midlatitude transient eddies. This paper examines how the eddy kinetic energy in midlatitude baroclinic zones responds to changes in radiative forcing in simulations with an idealized moist general circulation model. In a series of simulations in which the optical thickness of the longwave absorber is varied over a wide range, the eddy kinetic energy has a maximum for a climate with mean temperature similar to that of present-day earth, with significantly smaller values both for warmer and for colder climates. In a series of simulations in which the meridional insolation gradient is varied, the eddy kinetic energy increases monotonically with insolation gradient. In both series of simulations, the eddy kinetic energy scales approximately linearly with the dry mean available potential energy averaged over the baroclinic zones. Changes in eddy kinetic energy can therefore be related to the changes in the atmospheric thermal structure that affect the mean available potential energy.

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Recent Changes in the Pacific Subtropical Cells Inferred from an Eddy-Resolving Ocean Circulation Model*

Journal of Physical Oceanography ◽

10.1175/jpo3051.1 ◽

2007 ◽

Vol 37 (5) ◽

pp. 1340-1356 ◽

Cited By ~ 17

Author(s):

Wei Cheng ◽

Michael J. McPhaden ◽

Dongxiao Zhang ◽

E. Joseph Metzger

Keyword(s):

Ocean Circulation ◽

General Circulation ◽

Control Volume ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Volume Transport ◽

Western Boundary ◽

Equatorial Undercurrent ◽

Model Driven ◽

The Pacific

Abstract In this study the subtropical cells (STC) in the Pacific Ocean are analyzed using an eddy-resolving ocean general circulation model driven by atmospheric forcing for the years 1992–2003. In particular, the authors seek to identify decadal changes in the STCs in the model and to compare them with observations in order to understand the consequences of such changes for the equatorial ocean heat and mass budgets. The simulation shows a trend toward increasing pycnocline volume transport at 9°N and 9°S across the basin from 1992 to 2003. This increase [4.9 ± 1.0 Sv (Sv ≡ 106 m3 s−1)] is in qualitative agreement with observations and is attributed primarily to changes in the interior ocean transport, which are partially compensated by opposing western boundary transports. The subtropical meridional volume transport convergence anomalies in the model pycnocline are found to be consistent with anomalous volume transports in both the observed and modeled Equatorial Undercurrent, as well as with the magnitude of simulated anomalous upwelling transport at the base of the mixed layer in the eastern Pacific. As a result of the increased circulation intensity, heat transport divergence through the lateral boundaries of the tropical control volume (defined as the region between 9°N and 9°S, and from the surface to σθ = 25.3 isopycnal) increases, leading to a cooling of the tropical upper ocean despite the fact that net surface heat flux into the control volume has increased in the same time. As such, these results suggest that wind-driven changes in ocean transports associated with the subtropical cells play a central role in regulating tropical Pacific climate variability on decadal time scales.

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Downstream Self-Destruction of Storm Tracks

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-10-05002.1 ◽

2011 ◽

Vol 68 (10) ◽

pp. 2459-2464 ◽

Cited By ~ 22

Author(s):

Yohai Kaspi ◽

Tapio Schneider

Keyword(s):

Kinetic Energy ◽

Rotation Rate ◽

General Circulation ◽

Energy Transport ◽

Circulation Model ◽

Eddy Kinetic Energy ◽

Storm Tracks ◽

Planetary Rotation ◽

The Pacific ◽

Longitudinal Length

Abstract The Northern Hemisphere storm tracks have maximum intensity over the Pacific and Atlantic basins; their intensity is reduced over the continents downstream. Here, simulations with an idealized aquaplanet general circulation model are used to demonstrate that even without continents, storm tracks have a self-determined longitudinal length scale. Their length is controlled primarily by the planetary rotation rate and is similar to that of Earth’s storm tracks for Earth’s rotation rate. Downstream, storm tracks self-destruct: the downstream eddy kinetic energy is lower than it would be without the zonal asymmetries that cause localized storm tracks. Likely involved in the downstream self-destruction of storm tracks are the energy fluxes associated with them. The zonal asymmetries that cause localized storm tracks enhance the energy transport through the generation of stationary eddies, and this leads to a reduced baroclinicity that persists far downstream of the eddy kinetic energy maxima.

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Coupled Climate Simulation by Constraining Ocean Fields in a Coupled Model with Ocean Data

Journal of Climate ◽

10.1175/2009jcli2814.1 ◽

2009 ◽

Vol 22 (20) ◽

pp. 5541-5557 ◽

Cited By ~ 28

Author(s):

Yosuke Fujii ◽

Toshiyuki Nakaegawa ◽

Satoshi Matsumoto ◽

Tamaki Yasuda ◽

Goro Yamanaka ◽

...

Keyword(s):

Data Assimilation ◽

General Circulation ◽

Coupled Model ◽

Circulation Model ◽

Ocean General Circulation Model ◽

The Philippines ◽

Ocean Model ◽

Climate Simulation ◽

Philippine Sea ◽

Estimation System

Abstract The authors developed a system for simulating climate variation by constraining the ocean component of a coupled atmosphere–ocean general circulation model (CGCM) through ocean data assimilation and conducted a climate simulation [Multivariate Ocean Variational Estimation System–Coupled Version Reanalysis (MOVE-C RA)]. The monthly variation of sea surface temperature (SST) is reasonably recovered in MOVE-C RA. Furthermore, MOVE-C RA has improved precipitation fields over the Atmospheric Model Intercomparison Project (AMIP) run (a simulation of the atmosphere model forced by observed daily SST) and the CGCM free simulation run. In particular, precipitation in the Philippine Sea in summer is improved over the AMIP run. This improvement is assumed to stem from the reproduction of the interaction between SST and precipitation, indicated by the lag of the precipitation change behind SST. Enhanced (suppressed) convection tends to induce an SST drop (rise) because of cloud cover and ocean mixing in the real world. A lack of this interaction in the AMIP run leads to overestimating the precipitation in the Bay of Bengal in summer. Because it is recovered in MOVE-C RA, the overestimate is suppressed. This intensifies the zonal Walker circulation and the monsoon trough, resulting in enhanced convection in the Philippine Sea. The spurious positive correlation between SST and precipitation around the Philippines in the AMIP run in summer is also removed in MOVE-C RA. These improvements demonstrate the effectiveness of simulating ocean interior processes with the ocean model and data assimilation for reproducing the climate variability.

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Barotropic Impacts of Surface Friction on Eddy Kinetic Energy and Momentum Fluxes: An Alternative to the Barotropic Governor

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-11-0243.1 ◽

2012 ◽

Vol 69 (10) ◽

pp. 3028-3039 ◽

Cited By ~ 4

Author(s):

Elizabeth A. Barnes ◽

Chaim I. Garfinkel

Keyword(s):

Kinetic Energy ◽

Momentum Flux ◽

General Circulation ◽

Circulation Model ◽

Surface Friction ◽

Eddy Kinetic Energy ◽

Surface Drag ◽

Momentum Fluxes ◽

Upper Level ◽

Energy And Momentum

Abstract As the surface drag is increased in a comprehensive general circulation model (GCM), the upper-level zonal winds decrease and eddy momentum flux convergence into the jet core increases. Globally averaged eddy kinetic energy decreases, a response that is inconsistent with the conventional barotropic governor mechanism whereby decreased barotropic shears encourage baroclinic wave growth. As the conventional barotropic governor appears insufficient to explain the entire response in the comprehensive GCM, the nondivergent barotropic model on the sphere is used to demonstrate an additional mechanism for the effect of surface drag on eddy momentum fluxes and eddy kinetic energy. Analysis of the pseudomomentum budget shows that increased drag modifies the background meridional vorticity gradient, which allows for enhanced eddy momentum flux convergence and decreased eddy kinetic energy in the presence of a constant eddy source. This additional feedback may explain the changes in eddy momentum fluxes observed in the comprehensive GCM and was likely present in previous work on the barotropic governor.

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Performance evaluation for an ocean general circulation model: vectorization andmultitasking

Proceedings of the 2nd international conference on Supercomputing - ICS '88 ◽

10.1145/55364.55393 ◽

1988 ◽

Cited By ~ 1

Author(s):

P. Andrich ◽

G. Madec

Keyword(s):

Performance Evaluation ◽

General Circulation Model ◽

General Circulation ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Ocean General Circulation

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The South China Sea Throughflow Retrieved from Climatological Data*

Journal of Physical Oceanography ◽

10.1175/2008jpo3955.1 ◽

2009 ◽

Vol 39 (3) ◽

pp. 753-767 ◽

Cited By ~ 40

Author(s):

Max Yaremchuk ◽

Julian McCreary ◽

Zuojun Yu ◽

Ryo Furue

Keyword(s):

South China Sea ◽

General Circulation Model ◽

South China ◽

General Circulation ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Luzon Strait ◽

The South China Sea ◽

China Sea ◽

Ocean General Circulation

Abstract The salinity distribution in the South China Sea (SCS) has a pronounced subsurface maximum from 150–220 m throughout the year. This feature can only be maintained by the existence of a mean flow through the SCS, consisting of a net inflow of salty North Pacific tropical water through the Luzon Strait and outflow through the Mindoro, Karimata, and Taiwan Straits. Using an inverse modeling approach, the authors show that the magnitude and space–time variations of the SCS thermohaline structure, particularly for the salinity maximum, allow a quantitative estimate of the SCS throughflow and its distribution among the three outflow straits. Results from the inversion are compared with available observations and output from a 50-yr simulation of a highly resolved ocean general circulation model. The annual-mean Luzon Strait transport is found to be 2.4 ± 0.6 Sv (Sv ≡ 106 m3 s−1). This inflow is balanced by the outflows from the Karimata (0.3 ± 0.5 Sv), Mindoro (1.5 ± 0.4), and Taiwan (0.6 ± 0.5 Sv) Straits. Results of the inversion suggest that the Karimata transport tends to be overestimated in numerical models. The Mindoro Strait provides the only passage from the SCS deeper than 100 m, and half of the SCS throughflow (1.2 ± 0.3 Sv) exits the basin below 100 m in the Mindoro Strait, a result that is consistent with a climatological run of a 0.1° global ocean general circulation model.

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