Western boundary circulation driven by an alongshore wind: with application to the Somali Current system

1986 ◽  
Vol 33 (3) ◽  
pp. 205
Keyword(s):  
Current System ◽  
Western Boundary ◽  
Somali Current ◽  
Alongshore Wind

scholarly journals The INALT family – a set of high-resolution nests for the Agulhas Current system within global NEMO ocean/sea-ice configurations

2019 ◽  
Vol 12 (7) ◽  
pp. 3329-3355 ◽  
Author(s):  
Franziska U. Schwarzkopf ◽  
Arne Biastoch ◽  
Claus W. Böning ◽  
Jérôme Chanut ◽  
Jonathan V. Durgadoo ◽  
...  
Keyword(s):  
High Resolution ◽  
Boundary Conditions ◽  
Current System ◽  
Western Boundary Current ◽  
Global Ocean ◽  
Western Boundary ◽  
Boundary Current ◽  
The South ◽  
Agulhas Current ◽  
Mesoscale Dynamics

Abstract. The Agulhas Current, the western boundary current of the South Indian Ocean, has been shown to play an important role in the connectivity between the Indian and Atlantic oceans. The greater Agulhas Current system is highly dominated by mesoscale dynamics. To investigate their influence on the regional and global circulations, a family of high-resolution ocean general circulation model configurations based on the NEMO code has been developed. Horizontal resolution refinement is achieved by embedding “nests” covering the South Atlantic and the western Indian oceans at 1/10∘ (INALT10) and 1/20∘ (INALT20) within global hosts with coarser resolutions. Nests and hosts are connected through two-way interaction, allowing the nests not only to receive boundary conditions from their respective host but also to feed back the impact of regional dynamics onto the global ocean. A double-nested configuration at 1/60∘ resolution (INALT60) has been developed to gain insights into submesoscale processes within the Agulhas Current system. Large-scale measures such as the Drake Passage transport and the strength of the Atlantic meridional overturning circulation are rather robust among the different configurations, indicating the important role of the hosts in providing a consistent embedment of the regionally refined grids into the global circulation. The dynamics of the Agulhas Current system strongly depend on the representation of mesoscale processes. Both the southward-flowing Agulhas Current and the northward-flowing Agulhas Undercurrent increase in strength with increasing resolution towards more realistic values, which suggests the importance of improving mesoscale dynamics as well as bathymetric slopes along this narrow western boundary current regime. The exploration of numerical choices such as lateral boundary conditions and details of the implementation of surface wind stress forcing demonstrates the range of solutions within any given configuration.

scholarly journals Weak Thermocline Mixing in the North Pacific Low-Latitude Western Boundary Current System

2017 ◽  
Vol 44 (20) ◽  
pp. 10,530-10,539 ◽  
Author(s):  
Zhiyu Liu ◽  
Qiang Lian ◽  
Fangtao Zhang ◽  
Lei Wang ◽  
Mingming Li ◽  
...  
Keyword(s):  
North Pacific ◽  
Current System ◽  
Western Boundary Current ◽  
Western Boundary ◽  
Boundary Current ◽  
Low Latitude ◽  
The North ◽  
The North Pacific

Directional Extreme Current Profiles Based on Complex Empirical Orthogonal Functions (C-EOF) for Offshore Design

2009 ◽  
Author(s):  
Jose Antonio Moreira Lima ◽  
Eric Oliveira Ribeiro ◽  
Wellington Ceccopieri ◽  
Guisela Grossmann Matheson
Keyword(s):  
Goodness Of Fit ◽  
Structural Reliability ◽  
Current System ◽  
Correlation Coefficients ◽  
Current Data ◽  
Empirical Orthogonal Functions ◽  
Western Boundary ◽  
Boundary Current ◽  
Orthogonal Functions ◽  
Brazil Current

This paper presents a methodology to estimate deep water design current profiles using Complex Empirical Orthogonal Function (C-EOF) and a structural reliability response based model. The advantage of C-EOF is the capability of directly obtaining directional extreme current profiles. It is estimated that most of the variability of the southeast Brazil current system can be explained by the first two EOF modes. The first mode associated with the southwestward Brazil Current (BC) and the second mode with the northeastward Intermediate Western Boundary Current (IWBC). Thus, only two series of C-EOF amplitudes can be used in the response based technique to estimate the 100-y extreme current values. The methodology can also be used with more EOF modes if required to properly represent the current data. The probabilistic cumulative functions are based on extreme value distributions such as Gumbel or Weibull, and Lognormal for conditional distributions. The evaluation of estimated distribution parameters are carried out using Kolmogorov-Smirnov goodness-of-fit hypothesis tests and correlation coefficients for each directional sector.

scholarly journals Sea Surface Temperature and Wind Stress Curl Variability near a Cape

2012 ◽  
Vol 42 (11) ◽  
pp. 2073-2087 ◽  
Author(s):  
Renato M. Castelao
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Wind Stress ◽  
Current System ◽  
Empirical Orthogonal Functions ◽  
Sea Surface ◽  
Western Boundary ◽  
Surface Cooling ◽  
Wind Stress Curl ◽  
California Current System

Abstract The coupling between sea surface temperature (SST), SST gradients, and wind stress curl variability near a cape off Brazil is investigated using satellite observations and several different SST high-resolution analyses. The cape is characterized by strong SST fronts year-round, associated with upwelling and advection of warm water offshore in a western boundary current. Observations reveal a strong coupling between crosswind SST gradients and wind stress curl variability, with the predominantly negative crosswind gradients leading to negative, upwelling favorable wind stress curl anomalies. The spatial correlation between empirical orthogonal functions (EOF) of those variables is ~0.6, while the correlation between the EOF amplitude time series of the wind stress curl and crosswind SST gradients is larger than 0.7. The coupling occurs during summer and winter and is strongly modulated by variations in the wind stress directional steadiness. The intensity of the coupling is weaker than around capes on the California Current system, presumably because of higher variability in wind direction off Brazil. During periods of high wind stress directional steadiness off Cape Frio, the coupling is intensified by up to 40%–75%. Wind stress curl is also correlated with SST itself, especially in the vicinity of the cape, although not as strongly as with crosswind SST gradients. The analyses suggest that the observed wind stress curl anomalies can lead to surface cooling of as much as 1°C. If the enhanced upwelling leads to further strengthening of the upwelling front, negative wind stress curl anomalies may be intensified in a positive feedback mechanism.

scholarly journals Multiple Equilibria and Hysteresis of Two Unequal-Transport Western Boundary Currents Colliding at a Gap

2014 ◽  
Vol 44 (7) ◽  
pp. 1873-1885 ◽  
Author(s):  
Zheng Wang ◽  
Dongliang Yuan
Keyword(s):  
Multiple Equilibria ◽  
Current System ◽  
Ocean Model ◽  
Multiple Equilibrium ◽  
Western Boundary ◽  
Western Basin ◽  
Western Boundary Currents ◽  
Boundary Currents ◽  
Surface Drifters ◽  
Eddy Shedding

Abstract The nonlinear collision of two western boundary currents (WBCs) of Munk thickness LM colliding near a gap of width 2a is studied using a 1.5-layer, reduced-gravity, quasigeostrophic ocean model. The work is a continuation of our recent study on nonlinear collision of two equal-strength WBCs at a wide gap. It is found that, for narrow gaps, a < 5.7LM, and both of the WBCs fail to penetrate into the western basin due to the restriction of friction; for intermediate size gaps, 5.7LM ≤ a < 9.6LM, and multiple equilibrium states exist for the colliding WBCs: the penetrating state, the choking state, and the eddy-shedding state. The current system transits between them through a hysteresis procedure, with transitions at different Reynolds numbers from those in the equal-transport case. The stronger WBC tends to intrude more deeply into the western basin than the weaker WBC; for wide gaps, a > 9.6LM, and only penetrating and eddy-shedding states exist. No choking state is identified for either WBC. It is found that the critical gap width for the disappearance of the choking state decreases with the asymmetry of the WBC system. The theory is used to explain some of the circulation features at the entrance of the Indonesian Throughflow in the western Pacific Ocean recently observed with satellite-tracked surface drifters.

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