scholarly journals Feature Comparison of Two Mesoscale Eddy Datasets Based on Satellite Altimeter Data

2021 ◽  
Vol 14 (1) ◽  
pp. 116
Author(s):  
Zhiwei You ◽  
Lingxiao Liu ◽  
Brandon J. Bethel ◽  
Changming Dong
Keyword(s):  
Kuroshio Extension ◽  
Mesoscale Eddy ◽  
Region Of Interest ◽  
Global Ocean ◽  
Altimeter Data ◽  
Northwest Pacific ◽  
Coastal Current ◽  
Advantages And Disadvantages ◽  
Skewed Normal Distribution ◽  
Satellite Altimeter Data

Although a variety of ocean mesoscale eddy datasets are available for researchers to study eddy properties throughout the global ocean, subtle differences in how these datasets are produced often lead to large differences between one another. This study compares the Global Ocean Mesoscale Eddy Atmospheric-Oceanic-Biological interaction Observational Dataset (GOMEAD) with the well-recognized Mesoscale Eddy Trajectory Atlas in four regions with strong eddy activity: the Northwest Pacific Subtropical Front (SF), Kuroshio Extension (KE), South China Sea (SCS), and California Coastal Current (CC), and assesses the relative advantages and disadvantages of each. It was identified that while there is a slight difference in the total number of eddies detected in each dataset, the frequency distribution of eddy radii presents a right-skewed normal distribution, tending towards larger radii eddies, and there are more short- than long-lived eddies. Interestingly, the total number of GOMEAD eddies is 8% smaller than in the META dataset and this is most likely caused by the GOMEAD dataset’s underestimation of total eddy numbers and lifespans due to their presence near islands, and the tendency to eliminate eddies from its database if their radii are too small to be adequately detected. By contrast, the META dataset, due to tracking jumps in detecting eddies, may misidentify two eddies as a single eddy, reducing total number of eddies detected. Additionally, because the META dataset is reliant on satellite observations of sea surface level anomalies (SLAs), when SLAs are weak, the META dataset struggles to detect eddies. The GOMEAD dataset, by contrast, is reliant on applying vector geometry to detect and track eddies, and thus, is largely insulated from this problem. Thus, although both datasets are excellent in detecting and characterizing eddies, users should use the GOMEAD dataset when the region of interest is far from islands or when SLAs are weak but use the META dataset if the region of interest is populated by islands, or if SLAs are intense.

scholarly journals Random movement of mesoscale eddies in the global ocean

2020 ◽  
Author(s):  
Xiaoming Zhai ◽  
Qinbiao Ni ◽  
Guihua Wang ◽  
David Marshall
Keyword(s):  
Isotropic Turbulence ◽  
Mesoscale Eddy ◽  
Lateral Diffusion ◽  
Mesoscale Eddies ◽  
Global Ocean ◽  
Altimeter Data ◽  
High Latitudes ◽  
Turbulence Regime ◽  
Low Latitudes ◽  
Baroclinic Rossby Wave

<p>In this study we track and analyze eddy movement in the global ocean using 20 years of altimeter data and show that, in addition to the well-known westward propagation and slight polarity-based meridional deflections, mesoscale eddies also move randomly in all directions at all latitudes as a result of eddy-eddy interaction. The speed of this random eddy movement decreases with latitude and equals the baroclinic Rossby wave speed at about 25° of latitude. The tracked eddies are on average isotropic at mid and high latitudes, but become noticeably more elongated in the zonal direction at low latitudes. Our analyses suggest a critical latitude of approximately 25° that separates the global ocean into a low-latitude anisotropic wavelike regime and a high-latitude isotropic turbulence regime. One important consequence of random eddy movement is that it results in lateral diffusion of eddy energy. The associated eddy energy diffusivity, estimated using two different methods, is found to be a function of latitude. The zonal-mean eddy energy diffusivity varies from over 1500 m<sup>2</sup> s<sup>-1</sup> at low latitudes to around 500 m<sup>2</sup> s<sup>-1</sup> at high latitudes, but significantly larger values are found in the eddy energy hotspots at all latitudes, in excess of 5000 m<sup>2</sup> s<sup>-1</sup>. Results from this study have important implications for recently-developed energetically-consistent mesoscale eddy parameterization schemes which require solving the eddy energy budget.  </p>

Satellite Altimeter Data Assimilation in the Occam Global Ocean Model

1999 ◽  
pp. 365-369
Author(s):  
Alan D. Fox ◽  
Keith Haines ◽  
Beverly A. de Cuevas ◽  
Andrew C. Coward
Keyword(s):  
Data Assimilation ◽  
Ocean Model ◽  
Global Ocean ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Satellite Altimeter Data

A new automatic oceanic mesoscale eddy detection method using satellite altimeter data based on density clustering

2019 ◽  
Vol 38 (5) ◽  
pp. 134-141 ◽  
Author(s):  
Jitao Li ◽  
Yongquan Liang ◽  
Jie Zhang ◽  
Jungang Yang ◽  
Pingjian Song ◽  
...  
Keyword(s):  
Detection Method ◽  
Mesoscale Eddy ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Density Clustering ◽  
Satellite Altimeter Data ◽  
Eddy Detection

scholarly journals Random Movement of Mesoscale Eddies in the Global Ocean

2020 ◽  
Vol 50 (8) ◽  
pp. 2341-2357 ◽  
Author(s):  
Qinbiao Ni ◽  
Xiaoming Zhai ◽  
Guihua Wang ◽  
David P. Marshall
Keyword(s):  
Isotropic Turbulence ◽  
Mesoscale Eddy ◽  
Lateral Diffusion ◽  
Mesoscale Eddies ◽  
Global Ocean ◽  
Altimeter Data ◽  
High Latitudes ◽  
Turbulence Regime ◽  
Low Latitudes ◽  
Baroclinic Rossby Wave

AbstractIn this study we track and analyze eddy movement in the global ocean using 20 years of altimeter data and show that, in addition to the well-known westward propagation and slight polarity-based meridional deflections, mesoscale eddies also move randomly in all directions at all latitudes as a result of eddy–eddy interaction. The speed of this random eddy movement decreases with latitude and equals the baroclinic Rossby wave speed at about 25° of latitude. The tracked eddies are on average isotropic at mid- and high latitudes, but become noticeably more elongated in the zonal direction at low latitudes. Our analyses suggest a critical latitude of approximately 25° that separates the global ocean into a low-latitude anisotropic wavelike regime and a high-latitude isotropic turbulence regime. One important consequence of random eddy movement is that it results in lateral diffusion of eddy energy. The associated eddy energy diffusivity, estimated using two different methods, is found to be a function of latitude. The zonal-mean eddy energy diffusivity varies from over 1500 m2 s−1 at low latitudes to around 500 m2 s−1 at high latitudes, but significantly larger values are found in the eddy energy hotspots at all latitudes, in excess of 5000 m2 s−1. Results from this study have important implications for recently developed energetically consistent mesoscale eddy parameterization schemes which require solving the eddy energy budget.

On Quadratic Bottom Drag, Geostrophic Turbulence, and Oceanic Mesoscale Eddies

2008 ◽  
Vol 38 (1) ◽  
pp. 84-103 ◽  
Author(s):  
Brian K. Arbic ◽  
Robert B. Scott
Keyword(s):  
Mesoscale Eddy ◽  
Wave Drag ◽  
Ocean Model ◽  
Strength Parameter ◽  
Altimeter Data ◽  
Mean Flow ◽  
Quadratic Drag ◽  
Linear Drag ◽  
Geostrophic Turbulence ◽  
Satellite Altimeter Data

Abstract Many investigators have idealized the oceanic mesoscale eddy field with numerical simulations of geostrophic turbulence forced by a horizontally homogeneous, baroclinically unstable mean flow. To date such studies have employed linear bottom Ekman friction (hereinafter, linear drag). This paper presents simulations of two-layer baroclinically unstable geostrophic turbulence damped by quadratic bottom drag, which is generally thought to be more realistic. The goals of the paper are 1) to describe the behavior of quadratically damped turbulence as drag strength changes, using previously reported behaviors of linearly damped turbulence as a point of comparison, and 2) to compare the eddy energies, baroclinicities, and horizontal scales in both quadratic and linear drag simulations with observations and to discuss the constraints these comparisons place on the form and strength of bottom drag in the ocean. In both quadratic and linear drag simulations, large barotropic eddies develop with weak damping, large equivalent barotropic eddies develop with strong damping, and the comparison in goal 2 above is closest when the nondimensional friction strength parameter is of order 1. Typical values of the quadratic drag coefficient (cd ∼ 0.0025) and of boundary layer depths (Hb ∼ 50 m) imply that the quadratic friction strength parameter cdLd/Hb, where Ld is the deformation radius, may indeed be of order 1 in the ocean. Model eddies are realistic over a wider range of friction strengths when drag is quadratic, because of a reduced sensitivity to friction strength in that case. The quadratic parameter is independent of the mean shear, in contrast to the linear parameter. Plots of eddy length scales, computed from satellite altimeter data, versus mean shear and versus rough estimates of the friction strength parameters suggest that both linear and quadratic bottom drag may be active in the ocean. Topographic wave drag contains terms that are linear in the bottom flow, thus providing some justification for the use of linear bottom drag in models.

A Feasibility Demonstration of Ocean Model Eddy-resolving Nowcast/Forecast Skill Using Satellite Altimeter Data

2000 ◽  
Author(s):  
Harley E. Hurlburt ◽  
Robert C. Rhodes ◽  
Charlie N. Barron ◽  
E. J. Metzger ◽  
Ole M. Smedstad
Keyword(s):  
Ocean Model ◽  
Forecast Skill ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Satellite Altimeter Data

scholarly journals Geochronology and Geochemical Properties of Mid-Pleistocene Sediments on the Caiwei Guyot in the Northwest Pacific Imply a Surface-to-Deep Linkage

2021 ◽  
Vol 9 (3) ◽  
pp. 253
Author(s):  
Liang Yi ◽  
Haifeng Wang ◽  
Xiguang Deng ◽  
Haifan Yuan ◽  
Dong Xu ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Western Pacific ◽  
Global Ocean ◽  
Northwest Pacific ◽  
Local Circulation ◽  
Research Attention ◽  
Ice Volume ◽  
Global Ice Volume ◽  
Geochemical Properties ◽  
The Western Pacific

Seamounts are ubiquitous topographic units in the global ocean, and their effects on local circulation have attracted great research attention in physical oceanography; however, fewer relevant efforts were made on geological timescales in previous studies. The Caiwei (Pako) Guyot in the Magellan Seamounts of the western Pacific is a typical seamount and oceanographic characteristics have been well documented. In this study, we investigate a sediment core by geochronological and geochemical studies to reveal a topography-induce surface-to-bottom linkage. The principal results are as follows: (1) Two magnetozones are recognized in core MABC–11, which can be correlated to the Brunhes and Matuyama chrons; (2) Elements Ca, Si, Cl, K, Mn, Ti, and Fe are seven elements with high intensities by geochemical scanning; (3) Ca intensity can be tuned to global ice volume to refine the age model on glacial-interglacial timescales; (4) The averaged sediment accumulation rate is ~0.73 mm/kyr, agreeing with the estimate of the excess 230Th data in the upper part. Based on these results, a proxy of element Mn is derived, whose variability can be correlated with changes in global ice volume and deep-water masses on glacial-interglacial timescales. This record is also characterized by an evident 23-kyr cycle, highlighting a direct influence of solar insolation on deep-sea sedimentary processes. Overall, sedimentary archives of the Caiwei Guyot not only record an intensified abyssal ventilation during interglaciations in the western Pacific, but also provide a unique window for investigating the topography-induced linkage between the upper and bottom ocean on orbital timescales.

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