Improving the representation of internal wave processes in the Navy data assimilative forecasting system

PI: Eric Chassignet, Florida State University
Start Year: 2025 | Duration: 3  years
Partners: University of Michigan, Naval Research Laboratory

Project Abstract: 

The main objectives of this FSU-led proposal are to improve the accuracy of internal wave processes in the Navy data assimilative forecasting systems and to develop a 1/50 degree global HYCOM simulation with realistic and phase accurate internal waves as the first step towards an operational 1/50 degree global ocean model. The phase accuracy of the internal waves will be tested through comparison to wideswath (SWOT) and nadir altimetry, and the impacts of assimilating SWOT into HYCOM will be quantified. The 1/50 degree HYCOM simulations, global and Atlantic, will form the boundary condition for the regional simulations. There are several known issues with the current Navy ESPC forecasts that our group has been working on and this proposal aims to a) quantify the errors in the representation of internal tides and waves in the existing global 1/25 degree Navy system by taking advantage of the latest SWOT observational dataset and b) reduce these errors by improving the Navy system’s configuration, physics, and data assimilation. The latter will be achieved by systematically evaluating the impact of the bathymetry, bottom boundary layer, and horizontal/vertical resolution on the accuracy of internal tide/wave predictions and on the generation of high-frequency noise introduced by data assimilation. Our ultimate goal is to demonstrate the value-added of a kilometer-scale 1/50 degree global HYCOM simulation with realistic and phase accurate internal waves in generating boundary conditions for regional NCOM simulations and forecasts. The improvements in the HYCOM global modeling system will directly impact the US Navy’s ability to conduct regional modeling with boundary conditions that include remotely generated internal tides and waves. Both global HYCOM and the regional simulations driven by HYCOM internal wave boundary conditions will be tested with an array of in-situ observational assets. This proposal is a compendium of three collaborative proposals: (1) this  proposal “Improving the Representation of Internal Wave Processes in the Navy Data Assimilative Forecasting System”, (2) the USM-led proposal “Diagnosing and Validating Nonlinear Internal Wave Processes in Idealized, Regional, and Global Ocean Simulations” which aims to better understand the decay of the primary frequency internal tide due to wave-wave and wave-mean flow interactions and the generation of supertidal internal waves in global ocean, regional, and idealized model simulations, and  (3) the SIO-led proposal “A Distributed Network of Internal Wave Resolving Moored Arrays for Assessing Nonlinear Internal Wave Processes in Operational Forecast Models”, which focuses on the collection and analysis of in-situ data with full-water depth moorings and current- and pressure-sensor equipped inverted echo sounders (CPIESs) in regions with strong nonlinear internal wave generation and variable mesoscale.