Parametric Model for Eddies‐Induced Sound Speed Anomaly in Five Active Mesoscale Eddy Regions

Abstract

Mesoscale eddies are ubiquitous in the world's oceans. They are rotated with a 10-100 km length scale. The relatively isolated water mass trapped with mesoscale eddies can propagate a long distance while maintaining the source thermohaline characteristics. Thus, there are significant differences in the thermohaline structures between the inside and outside eddies, which have profound effects on underwater acoustic propagation.The earliest studies on the impact of eddies on sound propagation were conducted by Vastano and Owens (1973) and Weinberg and Zabalgogeazcoa (1977) based on hydrological field data measured from a cyclonic Gulf Stream (GS) ring detected in 1967. Vastano and Owens (1973) first observed the significant acoustic field perturbation caused by the cyclonic ring in the relatively uniform acoustic environment of the Sargasso Sea and found a strong dispersion phenomenon of the ray path in the area where the sound channel depth changed with the ray computations. In the following year, Gemmill studied the eddy's effects on the convergence mode of sound propagation and revealed that the cold eddy destroys the cyclic distribution of the convergence zones and refracts the sound rays into the deep sound channel. Subsequently, the eddy effects on ray travel time, which reflects the sound arrival structure, were studied with a range-dependent model presented by Weinberg and Zabalgogeazcoa (1977). Although the above studies are valuable, the corresponding sensitivity investigations of sound propagation on the eddy property variation cannot be conducted because of the rarity of eddy field data. To address this problem, Henrick et al. (1977) established a parametric eddy model qualitatively validated by GS ring observation data. Through the model, the effects of eddy intensity, geometric size and peak rotation speed on sound transmission are studied. Due to the good performance of such a model in describing eddy sound

Reconstruction of the Sound Speed Profile in Typical Sea Areas Based on the Single Empirical Orthogonal Function Regression Method

“…SSTA × SSTA I (mon) + p (2) SSTA (10) where p (1) and p (2) are calculated by the least squares method (LSM) method, and the coefficients p SSTA in ms −1 • C −1 denote the sensitivity of reconstruction error to SLA I and SSTA I , respectively. A bigger p (1) means a higher sensitivity.…”

“…For the in situ observation method, observational instruments, such as Argo buoys, expendable conductivity temperature depth (XCTD) [7], expendable bathythermograph (XBT) [8], and sound velocity profile (SVP) [9], are applied to obtain the hydrological parameters such as T, S, and pressure. Although this method can obtain the highest-accuracy SSP, conducting in situ experiments is difficult because they are resource-and time-consuming endeavors and are performed only by a small number of communities [10][11][12].…”

Mesoscale Eddy Effects on Vertical Correlation of Sound Field and Array Gain Performance

“…Various oceanic processes can disturb the sound speed profile (SSP), which is crucial in understanding the spatial correlation characteristics of the sound field with such spatiotemporal variations and their implications on the array gain [13]. With the development of satellite remote sensing technology, it is known that mesoscale eddies, pervasive in the ocean, significantly contribute to the kinetic energy of currents [14]. These eddies influence the distribution of temperature, salinity, density, and flow, thereby altering the structural features of SSP and subsequently impacting sound propagation [15,16].…”

Observation of a mesoscale warm eddy impacts acoustic propagation in the slope of the South China Sea

“…In the global oceans, mesoscale eddies are ubiquitous (Chelton et al, 2011). They are usually accompanied by temperature and salinity anomalies, and thus distort the sound speed profile (SSP) (Jian et al, 2009;Chen et al, 2022). Due to the significant abnormal sound fields, the impacts of mesoscale eddies on the acoustic properties gained considerable research attention.…”

“…Thus, based on the composite research, which combines Argo floats and satellite altimetry, the 3D structures of mesoscale eddies and their impacts on the acoustic characteristics are derived. Chen et al (2022) established a region-dependent parametric model for eddyinduced sound speed anomaly structure based on abundant Argo profiles. The parametric model can fast reconstruct the underwater sound speed field only using the satellite altimetry data.…”