Predictability and error growth dynamics of the Kuroshio Extension state transition process in an eddy-resolving regional ocean model

2020 ◽  
Vol 153 ◽  
pp. 101659
Author(s):  
Yu Geng ◽  
Qiang Wang ◽  
Mu Mu ◽  
Kun Zhang
Keyword(s):  
State Transition ◽  
Kuroshio Extension ◽  
Growth Dynamics ◽  
Transition Process ◽  
Ocean Model ◽  
Error Growth ◽  
Regional Ocean Model ◽  
The Kuroshio

scholarly journals Effects of Eddy Vorticity Forcing on the Mean State of the Kuroshio Extension

2015 ◽  
Vol 45 (5) ◽  
pp. 1356-1375 ◽  
Author(s):  
Andrew S. Delman ◽  
Julie L. McClean ◽  
Janet Sprintall ◽  
Lynne D. Talley ◽  
Elena Yulaeva ◽  
...  
Keyword(s):  
Reference Frames ◽  
Model Simulation ◽  
Kuroshio Extension ◽  
Relative Vorticity ◽  
Ocean Model ◽  
Instability Criterion ◽  
Mean Flow ◽  
Vorticity Budget ◽  
The Mean ◽  
The Kuroshio

AbstractEddy–mean flow interactions along the Kuroshio Extension (KE) jet are investigated using a vorticity budget of a high-resolution ocean model simulation, averaged over a 13-yr period. The simulation explicitly resolves mesoscale eddies in the KE and is forced with air–sea fluxes representing the years 1995–2007. A mean-eddy decomposition in a jet-following coordinate system removes the variability of the jet path from the eddy components of velocity; thus, eddy kinetic energy in the jet reference frame is substantially lower than in geographic coordinates and exhibits a cross-jet asymmetry that is consistent with the baroclinic instability criterion of the long-term mean field. The vorticity budget is computed in both geographic (i.e., Eulerian) and jet reference frames; the jet frame budget reveals several patterns of eddy forcing that are largely attributed to varicose modes of variability. Eddies tend to diffuse the relative vorticity minima/maxima that flank the jet, removing momentum from the fast-moving jet core and reinforcing the quasi-permanent meridional meanders in the mean jet. A pattern associated with the vertical stretching of relative vorticity in eddies indicates a deceleration (acceleration) of the jet coincident with northward (southward) quasi-permanent meanders. Eddy relative vorticity advection outside of the eastward jet core is balanced mostly by vertical stretching of the mean flow, which through baroclinic adjustment helps to drive the flanking recirculation gyres. The jet frame vorticity budget presents a well-defined picture of eddy activity, illustrating along-jet variations in eddy–mean flow interaction that may have implications for the jet’s dynamics and cross-frontal tracer fluxes.

A Comparison of Mesoscale Eddy Heat Fluxes from Observations and a High-Resolution Ocean Model Simulation of the Kuroshio Extension

2013 ◽  
Vol 43 (12) ◽  
pp. 2563-2570 ◽  
Author(s):  
Stuart P. Bishop ◽  
Frank O. Bryan
Keyword(s):  
High Resolution ◽  
Model Simulation ◽  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Ocean Model ◽  
Heat Fluxes ◽  
Dynamical Mechanism ◽  
Eddy Heat Flux ◽  
Conversion Rates ◽  
The Kuroshio

Abstract For the first time estimates of divergent eddy heat flux (DEHF) from a high-resolution (0.1°) simulation of the Parallel Ocean Program (POP) are compared with estimates made during the Kuroshio Extension System Study (KESS). The results from POP are in good agreement with KESS observations. POP captures the lateral and vertical structure of mean-to-eddy energy conversion rates, which range from 2 to 10 cm2 s−3. The dynamical mechanism of vertical coupling between the deep and upper ocean is the process responsible for DEHFs in POP and is in accordance with baroclinic instability observed in the Gulf Stream and Kuroshio Extension. Meridional eddy heat transport values are ~14% larger in POP at its maximum value. This is likely due to the more zonal path configuration in POP. The results from this study suggest that HR POP is a useful tool for estimating eddy statistics in the Kuroshio Extension region, and thereby provide guidance in the formulation and testing of eddy mixing parameterization schemes.

scholarly journals Effects of Singular-Vector-Type Initial Errors on the Short-Range Prediction of Kuroshio Extension Transition Processes

2017 ◽  
Vol 30 (15) ◽  
pp. 5961-5983 ◽  
Author(s):  
Qiang Wang ◽  
Youmin Tang ◽  
Stefano Pierini ◽  
Mu Mu
Keyword(s):  
Short Range ◽  
Singular Vector ◽  
Energy State ◽  
Kuroshio Extension ◽  
High Energy ◽  
Low Energy ◽  
Error Growth ◽  
Initial Error ◽  
Initial Errors ◽  
The Kuroshio

The effects of optimal initial error on the short-range prediction of transition processes between the Kuroshio Extension (KE) bimodalities are analyzed using a reduced-gravity shallow-water model and the singular vector (SV) approach. Emphasis is placed on the spatial structures, growing processes, and effects of the SVs. The results show that the large values of the SVs are mainly located in the first crest region of the KE (around 35°N, 144°E) and in the Kuroshio large meander (KLM) region south of Japan (around 32°N, 139.5°E). The fast growths of the SVs have important impacts on the prediction of transition of the KE bimodality. The initial error with +SV pattern (with positive anomalies in the first crest region of the KE and negative anomalies in the KLM region) tends to strengthen the KE and shift it toward the high-energy state, while the error with −SV pattern is prone to weaken the KE and shift it toward the low-energy state. In addition, the SV-type initial errors grow more quickly in the transition phase of the KE from the high-energy to the low-energy state than in the opposite transition phase. A perturbation energy analysis illustrates that different physical processes are responsible for the error growth in the KE region for different transition phases of the KE; barotropic instability plays a dominant role in the error growth in the low-to-high (LH) energy phase, while the error evolution in the high-to-low (HL) energy phase is mainly caused by advection processes.

scholarly journals The Predictability Limit of Ocean Mesoscale Eddy Tracks in the Kuroshio Extension Region

2021 ◽  
Vol 8 ◽  
Author(s):  
Yao Meng ◽  
Hailong Liu ◽  
Ruiqiang Ding ◽  
Pengfei Lin ◽  
Mengrong Ding ◽  
...  
Keyword(s):  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Growth Dynamics ◽  
Northern Region ◽  
Eastern Region ◽  
Limit Values ◽  
Surface Ocean ◽  
Large Size ◽  
High Predictability ◽  
The Kuroshio

In this study, the nonlinear local Lyapunov exponent and nonlinear error growth dynamics are employed to estimate the predictability limit of oceanic mesoscale eddy (OME) tracks quantitatively using three datasets. The results show that the mean predictability limit of OME tracks is about 53 days for cyclonic eddy (CE) and 52 days for anticyclonic eddy (AE) in the Kuroshio Extension (KE). The predictability limit varies spatially. The predictability limit of OME tracks is higher for the eastern region (about 62.5 days) than that for the western part (about 46 days). The CEs (AEs) predictability limit is relatively high in the southern (northern) region. Additionally, the lifetime, amplitude, and radius of OME are closely related to the predictability limit. The long-lived, large-amplitude, and large-sized OMEs tend to be more predictable. The eastern region often generates long-lived and large-size OMEs, thereby obtaining a higher predictability limit of OME tracks. Furthermore, the relationship between the predictability limit and the smoothness of the OME tracks was investigated using a metric to describe the track’s complexation. Usually, OMEs with high predictability limit values often show extender and smoother trajectories. The effects of the surface ocean circulations and the surface winds are also investigated. The strong and energetic currents lead to a short limitation in the west region.

scholarly journals Response of the Kuroshio Extension to Rossby Waves Associated with the 1970s Climate Regime Shift in a High-Resolution Ocean Model*

2005 ◽  
Vol 18 (15) ◽  
pp. 2979-2995 ◽  
Author(s):  
Bunmei Taguchi ◽  
Shang-Ping Xie ◽  
Humio Mitsudera ◽  
Atsushi Kubokawa
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Regime Shift ◽  
Rossby Waves ◽  
Kuroshio Extension ◽  
Ocean Model ◽  
Western Boundary ◽  
Climate Regime ◽  
Climate Regime Shift ◽  
The Kuroshio

Abstract The response of the Kuroshio Extension (KE) to large-scale Rossby waves remotely excited by wind stress changes associated with the 1970s climate regime shift is studied using a high-resolution regional ocean model. Two ensemble simulations are conducted: The control run uses monthly climatological forcing while, in the second ensemble, anomalous forcing is imposed at the model eastern boundary around 165°E derived from a hindcast of decadal changes in subsurface temperature and salinity using a coarser-resolution model of the Pacific basin. Near the KE, ocean adjustment deviates strongly from the linear Rossby wave dynamics. Most notably, the eastward acceleration of the KE is much narrower in meridional extent than that associated with the incoming Rossby waves imposed on the eastern boundary. This KE acceleration is associated with an enhanced potential vorticity (PV) gradient across the front that is consistent with the inertial western boundary layer theory: the arrival of the Rossby waves at the western boundary causes the eastward current to accelerate, leading to enhanced advection of low (high) PV water of subtropical (subarctic) origin along the western boundary layer. The meridional dipole of PV anomalies results in a pair of anomalous recirculations with a narrow eastward jet in between. A three-layer quasigeostrophic model is used to demonstrate this inertial adjustment mechanism. Finally, transient eddy activity increases significantly and the eddy momentum transport acts to strengthen the mean flow response. The result that ocean physical response to broad-scale atmospheric forcing is large near the KE front has important implications for fisheries research.

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