Status: this preprint was under review for the journal OS. A final paper is not foreseen.
Evidence of coastal trapped wave scattering using high-frequency
radar data in the Mid-Atlantic Bight
Kelsey Brunnerand Kamazima M. M. Lwiza
Abstract. Coastal trapped waves (CTWs) become scattered when they encounter irregular coastlines and bathymetry during propagation. Analytical and modeling studies have provided some information about the different types of shelf geometries that can induce scattering, but much of the CTW scattering process generally remains a large knowledge gap. Furthermore, CTW scattering has never before been directly identified with observations. High-frequency radar surface velocity data covering the Mid-Atlantic Bight (MAB) continental shelf provides unprecedented observations of CTWs within a region with a highly complex coastline and bathymetry. A combination of velocity vector maps from real vector empirical orthogonal function (R-EOF) analysis and phase maps from complex empirical orthogonal function (C-EOF) analysis allow the identification of CTW scattering by assuming each EOF mode corresponds to a CTW mode. Abrupt jumps in phase in association with magnitude amplification/reduction or directional rotation of velocity vectors are indications of scattering. Using these guidelines, Georges Bank, Hudson Shelf Valley, Delaware Bay mouth, Chesapeake Bay mouth, and the North Carolina shelf are identified as high scattering regions within the MAB. Furthermore, stratification is confirmed to increase scattering into progressively higher order modes through a cascading process by comparing winter and summer cases, which supports previous theoretical and numerical model predictions. The simple methodology used here can be applied to observations of CTWs on other coastlines around the world to identify additional scattering regions and help close the knowledge gap.
This preprint has been withdrawn.
How to cite. Brunner, K. and Lwiza, K. M. M.: Evidence of coastal trapped wave scattering using high-frequency
radar data in the Mid-Atlantic Bight, Ocean Sci. Discuss. [preprint], https://doi.org/10.5194/os-2020-46, 2020.
Received: 11 May 2020 – Discussion started: 02 Jul 2020
Coastal trapped waves (CTWs) are very long shallow water waves that propagate along the continental shelves of most major ocean basins. Their general properties are known but can be easily modified by changes in the coastline or other factors through a process known as scattering. Scattering is not well understood but can cause high surface velocities. For the first time, we directly observe CTW scattering using a simple mathematical technique that can be easily applied to other coastlines.
Coastal trapped waves (CTWs) are very long shallow water waves that propagate along the...