Influence of warm eddies on sound propagation in the Gulf of Mexico*

Abstract

An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to determine the spatio–temporal evolution of a strong warm eddy separated from the Mexico current. Then, the influence of this strong warm eddy on sound propagation during its lifespan are comprehensively analyzed with the parabolic equation and explained by using the normal mode and ray theories. Additionally, the influence of mesoscale eddies on the redistribution of total depth-integrated energy among the normal modes in the deep water is also discussed. The variation of arrival angle is investigated to explain the spreading acoustic energy caused by eddies. Overall, the results show that warm eddies can change the propagation paths and cause the convergence zone to broaden and approach the sound source. Moreover, the warm eddy can disperse sound energy and cause the total depth-integrated energy to incline to a lower normal mode. Throughout the whole of these three periods (eddy generating, eddy maturing, and eddy terminating), the fluctuation in the transmission loss is up to 30 dB (depending on the relative location of eddy center to the source).

Electrochemical pH sensing characteristics of nitrogen‐doped zinc oxide nanostructures using a screen‐printed platform**

“…The generation of the surface species can be explained by the mechanism below. ZnO is intrinsically an n‐type semiconducting material, that when doped with nitrogen, is found to generate more p‐type charge carriers [29, 31, 49]. The native defects in ZnO include both donor like and acceptor like defects.…”

“…The native defects in ZnO include both donor like and acceptor like defects. Among these oxygen vacancies (V O ), zinc interstitials (Zn i ) and Zn O (antisites) are considered donor‐like defects making ZnO n‐type, whereas zinc vacancies (Zn V ), oxygen interstitials (O i ), and O Zn (antisites) are considered acceptor like defects making ZnO p‐type [49]. However, in both Zn‐rich and O‐rich environments, acceptor‐like defects are compensated by the lower formation energies of donor‐like defects.…”

Effects of mesoscale eddies on the spatial coherence of a middle range sound field in deep water

“…[10] With the development of theoretical acoustic models and underwa-ter acoustic experiments in deep water, many features have been interpreted theoretically and validated with in situ acoustic data and synchronous hydrographic data. [11,12] It has been found that mesoscale eddies can change the normal modes or the propagation path of acoustic rays. Meanwhile, the impacts of mesoscale eddies on long-range acoustic deflection, pulse width and arrival patterns have also been studied using highresolution ocean reanalysis data or ocean models, [13,14] indicating that the eddies make the arrival patterns of sound fields complex so that it is hard to resolve individual arrivals.…”

Mesoscale eddies and their dispersive environmental impacts in the Persian Gulf

“…[12] As warm or cold water transferred by mesoscale eddies can change the temperature and distribution of salinity, they can even significantly change the profile structure of sound speed, so they also affect the propagation of sound underwater. [13] Temperature, salinity, and pressure gradients generated by mesoscale eddies can also change the structure of the sound speed in the ocean. [13] When eddies exchange water slantwise across a front, they perform in an advective manner, result in the creation of baroclinic instability, and make tracers to move convectively.…”

“…[13] Temperature, salinity, and pressure gradients generated by mesoscale eddies can also change the structure of the sound speed in the ocean. [13] When eddies exchange water slantwise across a front, they perform in an advective manner, result in the creation of baroclinic instability, and make tracers to move convectively. [12] Physical conditions can be locally changed by the dynamics of eddies, as a result, reactive tracers such as phytoplankton can be directly or indirectly affected.…”