A distributed network of internal wave resolving moored arrays for assessing nonlinear internal wave processes in operational forecast models

PI: Andrew Lucas, UC San Diego Scripps Institute of Oceanography
Start Year: 2025 | Duration: 3  years
Partners: Woods Hole Oceanographic Institution, University of Massachusetts; NASA Jet Propulsion Laboratory

Project Abstract: 

This proposal aims to quantify the decay of primary-frequency internal tides due to wave- wave and wave-mean flow interactions. We will use a combination of global, regional, and idealized model simulations, validated by in situ and satellite observations. Key observational data will be provided by full-depth moorings, CPIES, satellite swath altimetry (SWOT), and satellite synthetic aperture radar (NISAR).  While previous studies have focused on Parametric Subharmonic Instabilities (PSI), this work emphasizes the “superharmonic cascade,” where primary-frequency internal tides inter- act to generate higher harmonic (supertidal) waves. This process, particularly pronounced in the tropics, leads to solitary wave-train formation that impact Navy operations and underwater acoustics. Internal tides also decay via wave-mean-flow interactions and scattering in eddy-rich regions. It is unclear how accurately any of these nonlinear processes are represented in the regional and global ocean models that provide operational forecasts for the US Navy. Here, we propose to quantify the impacts and accuracy of nonlinear processes in existing and next-generation global and regional model simulations. To accomplish these goals, we will (1) conduct high-resolution measurements of nonlinear processes in internal-tide beams radiating from strong generation sites in tropical regions with and without strong mesoscale eddy activity, (2) contextualize these in situ observations globally with satellite remote sensing, and (3) perform high-resolution idealized, regional, and global simulations in synergy with the observations.  The overall program is comprised of three collaborative, but separately proposed, projects: 1. Scripps Institution of Oceanography led: In-situ data collection and analysis using moorings, CPIES, and satellites in regions of strong nonlinear internal wave activity globally (this proposal). 2. University of Southern Mississippi led: High-resolution modeling of internal-tide decay mechanisms in idealized, regional, and global simulations (Buijsman, lead PI). 3. Florida State University led: Evaluation and improvement of internal wave representation in the Navy’s data assimilative forecast system using SWOT observations (Chassignet, lead PI).  Our joint efforts will increase the fidelity of US Navy global HYCOM simulations and forecasts, enable HYCOM to assimilate SWOT data, and improve the ability of HYCOM to provide useful boundary conditions to regional simulations run by the US Navy. The project will also strengthen and deepen collaborations between the HYCOM team and ocean observationalists, as well as between Navy- and NASA-funded research.