Global Sea Surface Cyclogeostrophic Currents Derived From Satellite Altimetry Data

Cao, Yuhan; Stegner, Alexandre; Bethel, Brandon J.; Li, Chunyan; Dong, Jihai; Lü, Haibin; Yang, Jingsong

doi:10.1029/2022jc019357

Cited by 4 publications

(3 citation statements)

References 29 publications

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“…These differences might be due to the fact that NBC rings do not necessarily satisfy entirely the geostrophic equilibrium, considering that their mean Rossby number is 0.17. In some cases, cyclostrophy might be important enough as discussed by [68,69].…”

Section: Comparison Between In-situ and Satellite-derived Surface Geo...mentioning

confidence: 99%

Combining an Eddy Detection Algorithm with In-Situ Measurements to Study North Brazil Current Rings

et al. 2023

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North Brazil Current (NBC) rings are believed to play a key role in the Atlantic Ocean circulation and climate. Here, we use a new collection of high-resolution in-situ observations acquired during the EUREC4A-OA field experiment together with satellite altimetry to define, with unprecedented detail, the structure and evolution of these eddies. In-situ observations reveal a more complex structure than previously documented. In particular, we highlight a measurable impact of the Amazon outflow in creating a barrier layer over a large portion of the eddies. We show that this unprecedented data set allows us to estimate the accuracy of satellite altimetry gridded fields. The geostrophic velocities derived from satellite altimetry turn out to be considerably lower (up to 50% in amplitude) than the values measured by current meters. However, eddy properties as detected by TOEddies, a newly developed algorithm show to be relatively precise. For example, the eddy center and maximum azimuthal velocity contour fall within 25 ± 5 km and 16 ± 9 km, respectively, from the in-situ observed values. We apply TOEddies to 27 years of satellite altimetry to investigate the generic NBC rings behavior. We found a mean generation rate of 4.5 ± 1.1 rings per year, and a strong seasonal cycle in all eddy properties.

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Section: Comparison Between In-situ and Satellite-derived Surface Geo...mentioning

confidence: 99%

Combining an Eddy Detection Algorithm with In-Situ Measurements to Study North Brazil Current Rings

et al. 2023

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“…Figure 1f shows that the zonally averaged

{E}_{g}^{D}

agrees quite well with

{E}_{g}^{A}

, except at mid‐latitudes, where the background flows and eddies are strong (e.g., the Kuroshio, Gulf Stream, and Antarctic Circumpolar Current, hereafter ACC). The discrepancy could be partly explained by the cyclogeostrophy of strong eddies, for which the geostrophic estimates of EKE from AVISO might have relatively large errors (see, e.g., Cao et al., 2023). To summarize, the above results show that the present drifter data set can generally capture well the geostrophic velocity and EKE, especially inside the eddies ( R n < 1.5).…”

Section: Resultsmentioning

confidence: 99%

Energy Transfer Between Mesoscale Eddies and Near‐Inertial Waves From Surface Drifter Observations

Liu,

Chen,

et al. 2023

Geophysical Research Letters

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Hourly satellite‐tracked surface drifter data are utilized to study energy transfer from eddies to Near‐Inertial Waves (NIWs). Spatial velocity gradients are computed from two consecutive velocity estimates derived from the same drifter, providing variable spatial resolutions of O(1 km). The eddy‐to‐NIW energy transfer can be positive or negative, with the positive transfer (forward energy cascade) dominant. The global integrated energy transfer rate (ε) is 0.025 TW, with the anticyclonic eddy contribution dominant over the cyclonic eddy contribution. Given that the global near‐inertial wind work (W) is 0.2 TW, the eddy‐to‐NIW energy transfer efficiency (ε/W) is about 13%, which is one order of magnitude larger than that in low resolution simulations. This result may still underestimate the Eulerian energy transfer by a factor of 2. To our knowledge, this is the first time that this energy transfer is calculated from global drifter observations, providing a baseline for comparison in future studies.

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“…In addition, SSH is also one of the relevant elements of ocean surface currents which can reflect the movement of surface currents. The altimeters are also commonly used to estimate surface currents (Lagerloef et al, 1999;Bonjean and Lagerloef, 2002;Johnson et al, 2002;Cao et al, 2023b), so the forecasting effect is significantly enhanced by adding SSH.…”

Section: Analysis Of Multi-element Feature Fusionmentioning

confidence: 99%

ASTMEN: an adaptive spatiotemporal and multi-element fusion network for ocean surface currents forecasting

Li,

Wang,

Song

et al. 2023

Front. Mar. Sci.

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Accurate forecasting of ocean surface currents is crucial for the planning of marine activities, including fisheries, shipping, and pollution control. Previous studies have often neglected the consideration of spatiotemporal correlations and interdependencies among ocean elements, leading to suboptimal accuracy in medium to long-term forecasts, especially in regions characterized by intricate ocean currents. This paper proposes an adaptive spatiotemporal and multi-element fusion network for ocean surface currents forecasting (ASTMEN). Specifically, we use an improved Swin Transformer (Swin-T) to perform self-attention computation at any given moment, enabling the adaptive generation of multi-element time series with spatial dependencies. Then, we utilize a Long Short-Term Memory network (LSTM) to encode and decode these series in the dimensions of temporal and multi-element features, resulting in accurate forecasts of ocean surface currents. This study takes the Kuroshio region in the northwest Pacific Ocean as the study area with data from the ocean reanalysis dataset. The experimental results show that ASTMEN significantly outperforms the baseline model and the climate state method, and is the only model whose correlation coefficient is still higher than 0.8 at day 12. In the experiments during the summer, when the currents are most variable, ASTMEN provides better forecasts at the sea-land interface and at the junction of different currents, which has the potential to fill the gap of poor forecast performance of previous methods for complex current fields.

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Global Sea Surface Cyclogeostrophic Currents Derived From Satellite Altimetry Data

Abstract: Satellite altimeters are valuable tools for exploring and monitoring the state of the ocean. It is one of the most effective methods for global observations of ocean surface parameters such as sea surface height anomalies (SSHA) and sea surface currents (SSC) fields (

Cited by 4 publications

References 29 publications

Combining an Eddy Detection Algorithm with In-Situ Measurements to Study North Brazil Current Rings

Combining an Eddy Detection Algorithm with In-Situ Measurements to Study North Brazil Current Rings

Energy Transfer Between Mesoscale Eddies and Near‐Inertial Waves From Surface Drifter Observations

ASTMEN: an adaptive spatiotemporal and multi-element fusion network for ocean surface currents forecasting

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