ROXSI: ROcky shores eXperiments and SImulations
Abstract
The goal of ROXSI (ROcky shores eXperiments and SImulations) is to study the coastal ocean dynamical processes of rocky shores impor tant to Navy operations through combined in situ and remote sensing observations, and high-fidelity CFD and community models. About 75% of the worlds coastlines are rocky, limiting current Naval accessibility. By avoiding these rocky shores, the Navy is predicta ble. In contrast to well-studied sandy shores, rocky shores are inherently multiscale with complex three-dimensional (3D) geometries at scales of cm to 100s m. Multi-scale bottom variability has strong effects on wave processes, such as scattering, reflection, non linear energy transfers, and dissipation that are dramatically different than on sandy beaches. Rocky shores are exposed to large wa ves that strongly affect water-column turbulence and wave-driven inner shelf and surf zone currents (rip currents, undertow). The ap plicability of existing models developed for low-sloped, sandy beaches in predicting rocky shores wave propagation, circulation and turbulence is unknown, nor is what new physics must be included to make accurate predictions. As part of ROXSI, four central C rnia field experiments will occur from Big Sur to Santa Cruz spanning different canonical rocky shores types, based on bottom roughn ess from existing highresolution bathymetric surveys, shoreline type and complexity, wave climate, local knowledge, and logistics. T hese field sites are representative of rocky shores found worldwide. The proposed experiments use nested in situ arrays together wit h remote sensing to capture wave and circulation gradients and processes at different scales. The arrays will extend from 40-m water depth through the intertidal zone and span a few kilometers in the alongshore. The instrument arrays will be arranged along lines p arallel and perpendicular to shore to synchronously and asynchronously measure wave transformation and circulation patterns across s cales of 10 m - 1 km. For <10 m scale, a small-scale coherent array will be deployed around rocky obstacles to make detailed measure ments of processes that dissipate energy and alter wave properties. Ground- and UASbased lidar and optical remote sensing will measu re the time-evolving 2D wave field from the intertidal to offshore, capturing the transformation of nonlinear directionally-spread w aves propagating over complex rocky bathymetry, wave breaking and dissipation, and wave-induced currents via foam streaks. Vessel-ba sed observations and surface drifters will augment in situ moorings and ground-truth remote sensing measures. A suite of numerical m odel simulations will quantify fundamental water column processes, wave transformation and circulation dynamics on rocky shores. Hig E model simulations will determine the relative importance of wave scattering and dissipation due to bottom friction, and improve ex isting parameterizations in community wave models SWAN and WAVEWATCH III (WW3). Also, NHWAVE and COAWST (consisting of ROMS and SWAN /WW3) model simulations at a resolution of O(1-5 m) will be configured for the four field study sites to determine ideal instrument deployment design, and will be validated against observations from the inner-shelf to the intertidal zone. These comparisons will p rovide further improvements to parameterizations for wave scattering and dissipation due to bottom friction. Finally, high resolutio n SOMAR LES, at a resolution of O (0.01-2 m) and NHWAVE run at typical wave propagation scales will examine internal wave processes on rocky shores, and determine the applicability and limitations of hydrostatic community models such as ROMS.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 03, 2021
- Source ID
- N000142112786
Entities
People
- Falk Feddersen
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego