scholarly journals An undercurrent off the east coast of Sri Lanka

Ocean Science ◽  
2017 ◽  
Vol 13 (6) ◽  
pp. 1035-1044 ◽  
Author(s):  
Arachaporn Anutaliya ◽  
Uwe Send ◽  
Julie L. McClean ◽  
Janet Sprintall ◽  
Luc Rainville ◽  
...  
Keyword(s):  
Sri Lanka ◽  
Bay Of Bengal ◽  
General Circulation ◽  
East Coast ◽  
Subsurface Layer ◽  
Circulation Model ◽  
Surface Current ◽  
General Circulation Models ◽  
Salt Transport ◽  
Ocean General Circulation

Abstract. The existence of a seasonally varying undercurrent along 8° N off the east coast of Sri Lanka is inferred from shipboard hydrography, Argo floats, glider measurements, and two ocean general circulation model simulations. Together, they reveal an undercurrent below 100–200 m flowing in the opposite direction to the surface current, which is most pronounced during boreal spring and summer and switches direction between these two seasons. The volume transport of the undercurrent (200–1000 m layer) can be more than 10 Sv in either direction, exceeding the transport of 1–6 Sv carried by the surface current (0–200 m layer). The undercurrent transports relatively fresher water southward during spring, while it advects more saline water northward along the east coast of Sri Lanka during summer. Although the undercurrent is potentially a pathway of salt exchange between the Arabian Sea and the Bay of Bengal, the observations and the ocean general circulation models suggest that the salinity contrast between seasons and between the boundary current and interior is less than 0.09 in the subsurface layer, suggesting a small salt transport by the undercurrent of less than 4 % of the salinity deficit in the Bay of Bengal.

scholarly journals An Undercurrent off the East Coast of Sri Lanka

2017 ◽  
Author(s):  
Arachaporn Anutaliya ◽  
Uwe Send ◽  
Julie L. McClean ◽  
Janet Sprintall ◽  
Luc Rainville ◽  
...  
Keyword(s):  
Sri Lanka ◽  
General Circulation ◽  
East Coast ◽  
Saline Water ◽  
Circulation Model ◽  
Surface Current ◽  
Ocean General Circulation Model ◽  
Maximum Speed ◽  
Surface Circulation ◽  
Temperature Depth

Abstract. The existence of a seasonally varying undercurrent along 8° N off the east coast of Sri Lanka is inferred from Conductivity-Temperature-Depth profiles, Argo floats, glider measurements, and Ocean General Circulation Model outputs. Together, they reveal an undercurrent below 200 m that is approximately 140 km wide and can reach a maximum speed of 45 cm s−1 that hitherto has not been observed. The undercurrent, flowing in the opposite direction to the surface current, is most pronounced during boreal spring and summer and switches direction between these two seasons. The undercurrent transports relatively fresh water southward during spring, while it advects more saline water northward along the east coast of Sri Lanka during summer. This suggests a pathway, independent of the surface circulation, whereby freshwater is removed and saline water is injected into the Bay of Bengal.

Event detection and visualization of ocean eddies simulated by ocean general circulation model

2019 ◽  
Vol 10 (03) ◽  
pp. 1950018
Author(s):  
Daisuke Matsuoka ◽  
Fumiaki Araki ◽  
Hideharu Sasaki
Keyword(s):  
High Resolution ◽  
General Circulation ◽  
Numerical Study ◽  
Circulation Model ◽  
General Circulation Models ◽  
Ocean Currents ◽  
Time Step ◽  
Data Set ◽  
Ocean Eddies ◽  
Ocean General Circulation

Numerical study of ocean eddies has been carried out by using high-resolution ocean general circulation models. In order to understand ocean eddies from the large volume data produced by simulations, visualizing only eddy distribution at each time step is insufficient; time-variations in eddy events and phenomena must also be considered. However, existing methods cannot precisely find and track eddy events such as amalgamation and bifurcation. In this study, we propose an original approach for eddy detection, tracking, and event visualization based on an eddy classification system. The proposed method detects streams and currents as well as eddies, and it classifies discovered eddies into several categories using the additional stream and current information. By tracking how the classified eddies vary over time, detecting events such as eddy amalgamation and bifurcation as well as the interaction between eddies and ocean currents becomes achievable. We adopt the proposed method for two ocean areas in which strong ocean currents exist as case studies. We visualize the detected eddies and events in a time series of images, allowing us to acquire an intuitive understanding of a region of interest concealed in a high-resolution data set. Furthermore, our proposed method succeeded in clarifying the occurrence place and seasonality of each type of eddy event.

scholarly journals The atmosphere-ocean general circulation model EMAC-MPIOM

2011 ◽  
Vol 4 (1) ◽  
pp. 457-495 ◽  
Author(s):  
A. Pozzer ◽  
P. Jöckel ◽  
B. Kern ◽  
H. Haak
Keyword(s):  
General Circulation Model ◽  
Atmospheric Chemistry ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
General Circulation Models ◽  
Ocean General Circulation Model ◽  
Coupling Method ◽  
Model Systems ◽  
Ocean General Circulation

Abstract. The ECHAM/MESSy Atmospheric Chemistry (EMAC) model is coupled to the ocean general circulation model MPIOM using the Modular Earth Submodel Sytem (MESSy) interface. MPIOM is operated as a MESSy submodel, thus the need of an external coupler is avoided. The coupling method is tested for different model configurations, proving to be very flexible in terms of parallel decomposition and very well load balanced. The run time performance analysis and the simulation results are compared to those of the COSMOS (Community earth System MOdelS) climate model, using the same configurations for the atmosphere and the ocean in both model systems. It is shown that our coupling method is, for the tested conditions, approximately 10% more efficient compared to the coupling based on the OASIS (Ocean Atmosphere Sea Ice Soil, version 3) coupler. The standard (CMIP3) climate model simulations performed with EMAC-MPIOM show that the results are comparable to those of other Atmosphere-Ocean General Circulation models.

scholarly journals Optimal 3D Time-Energy Trajectory Planning for AUVs using Ocean General Circulation Models

2020 ◽  
Author(s):  
Sultan Albarakati ◽  
Ricardo Lima ◽  
thomas Theussl ◽  
Ibrahim Hoteit ◽  
Omar Knio
Keyword(s):  
Trajectory Planning ◽  
General Circulation ◽  
Autonomous Underwater Vehicles ◽  
Circulation Model ◽  
General Circulation Models ◽  
Optimal Time ◽  
Time Problem ◽  
Ocean General Circulation ◽  
Time And Energy ◽  
Planning Problems

<p>We develop a new approach for solving optimal time and energy-trajectory planning problems for Autonomous Underwater Vehicles (AUVs) in transient, 3D ocean currents. Realistic forecasts using an Ocean General Circulation Model (OGCM) are used for this purpose. The approach is based on decomposing the problem into a minimal time problem, followed by minimal energy subproblems. In both cases, a Non-Linear Programming (NLP) formulation is adopted. The methodology is first tested in idealized, steady, 2D settings, to verify the effectiveness of the method in addressing the multi-objective optimization problem. The scheme is then demonstrated for time-energy trajectory planning problems in the Gulf of Aden. In particular, the numerical experiments illustrate the capability of generating Pareto optimal solutions in a broad range of mission durations. In addition, the analysis also highlights how the methodology effectively exploits both the vertical structure of the current field, as well as its unsteadiness, namely, to minimize travel time and energy consumption.</p>

scholarly journals Impact of Climate Drift on Twenty-First-Century Projection in a Coupled Atmospheric–Ocean General Circulation Model

2013 ◽  
Vol 70 (10) ◽  
pp. 3321-3327 ◽  
Author(s):  
Mao-Chang Liang ◽  
Li-Ching Lin ◽  
Ka-Kit Tung ◽  
Yuk L. Yung ◽  
Shan Sun
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
General Circulation Models ◽  
Forced Response ◽  
First Century ◽  
Intergovernmental Panel ◽  
Climate Drift ◽  
Ocean General Circulation ◽  
Twenty First Century ◽  
The Impact

Abstract Reducing climate drift in coupled atmosphere–ocean general circulation models (AOGCMs) usually requires 1000–2000 years of spinup, which has not been practical for every modeling group to do. For the purpose of evaluating the impact of climate drift, the authors have performed a multimillennium-long control run of the Goddard Institute for Space Studies model (GISS-EH) AOGCM and produced different twentieth-century historical simulations and subsequent twenty-first-century projections by branching off the control run at various stages of equilibration. The control run for this model is considered at quasi equilibration after a 1200-yr spinup from a cold start. The simulations that branched off different points after 1200 years are robust, in the sense that their ensemble means all produce the same future projection of warming, both in the global mean and in spatial detail. These robust projections differ from the one that was originally submitted to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), which branched off a not-yet-equilibrated control run. The authors test various common postprocessing schemes in removing climate drift caused by a not-yet-equilibrated ocean initial state and find them to be ineffective, judging by the fact that they differ from each other and from the robust results that branched off an equilibrated control. The authors' results suggest that robust twenty-first-century projections of the forced response can be achieved by running climate simulations from an equilibrated ocean state, because memory of the different initial ocean state is lost in about 40 years if the forced run is started from a quasi-equilibrated state.

Visualization Strategies for Optimal 3D Time-Energy Trajectory Planning for AUVs using Ocean General Circulation Models

2020 ◽  
Author(s):  
Thomas Theussl ◽  
Sultan Albarakati ◽  
Ricardo Lima ◽  
Ibrahim Hoteit ◽  
Omar Knio
Keyword(s):  
Trajectory Planning ◽  
General Circulation ◽  
Autonomous Underwater Vehicles ◽  
Circulation Model ◽  
General Circulation Models ◽  
Ocean General Circulation Model ◽  
Optimal Time ◽  
Ocean General Circulation ◽  
Dependent Flow ◽  
Time And Energy

<p>In this presentation, we discuss visualization strategies for optimal time and energy trajectory planning problems for Autonomous Underwater Vehicles (AUVs) in transient 3D ocean currents. Realistic forecasts using an Ocean General Circulation Model (OGCM) are used to define time and energy optimal AUV trajectory problems in 2D and 3D. The visualization goal is to explore and explain the trajectory the AUV follows, especially how it exploits both the vertical structure of the current field as well as its unsteadiness to minimize travel time and energy consumption. We present our choice of visualization tools for this purpose and discuss shortcomings and possible improvements, especially for challenging scenarios involving 3D time-dependent flow and realistic bathymetry.</p>

Numerical Simulation of Bay of Bengal Circulation Features from Ocean General Circulation Model

2009 ◽  
Vol 32 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Saheb Paul ◽  
Arun Chakraborty ◽  
P. C. Pandey ◽  
Sujit Basu ◽  
S. K. Satsangi ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
General Circulation Model ◽  
Bay Of Bengal ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Ocean General Circulation

scholarly journals The South China Sea Throughflow Retrieved from Climatological Data*

2009 ◽  
Vol 39 (3) ◽  
pp. 753-767 ◽  
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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