Island Arc Turbulent Eddy Regional Exchange
Abstract
We propose to quantitatively study processes and predictability in the mesoscale and sub-mesoscale eddy field in the region between the Luzon and Marianas Island Arcs in the northwestern Pacific by implementing a hierarchy of nested data-assimilative models (state estimates) targeting multiple space- and time-scales. We will use the MIT general circulation model and its adjoint-based four-dime nsional variational assimilation (MITgcm-4DVAR) system. An outer parent model with a horizontal resolution of 1/12o (9 km) and 50 ve rtical levels covering the northwestern Pacific Ocean will be implemented to estimate/predict the large-scale regional circulation b y initializing using HYCOM/NCODA global analysis and adjusting initial conditions, boundary conditions and atmospheric forcings to m atch the data over one to three months.We will nest data-assimilative models into the large-scale model with increased resolution fo r horizontal grid scales down to 1/96o (1.2 km), and perhaps below, depending on the physics and on the observations available, and will be using shorter correlation lengths for the control adjustment and shorter assimilation windows. In addition to observations f rom global ocean observing system, we will assimilate the experimental data and produce reanalysis before, during, and after the fie ldwork. We will compute adjoint sensitivities of key circulation features to both local and remote ocean-atmospheric forcing. Specif ic science questions to be addressed:What are the characteristics of the three-dimensional structure of meso/sub-mesoscale eddies i n the proposed study region? Understanding the unique dynamic and thermodynamic properties of the eddies will quantify eddy net heat and mass transport. How do the model sub-grid scale parametrizations affect the sub-mesoscale energy cascade? Using different sub- grid scale parametrizations in high-resolution models will help to examine the mesoscale/sub-mesoscale energy cascade.What are the temporal and spatial scales of the sub-mesoscale cascade in the proposed study region? The spatial-temporal scales of the processes define the assimilation period and predictability times. Understanding the model errors/limitations: Model errors due to unresolved physics and parameterizations will cause representational error and limit the assimilation time. A key research goal is for an opti mal choice of assimilation window that produces skillful analysis and forecasts.We will be updating our existing 1/6o model for the northwestern Pacific (developed for the OKMC and FLEAT ONR DRIs) to 1/120 and will be nesting high-resolution submodels into 1/120 m odel. Using this 1/6o model, we performed state estimation/prediction experiments and produced skillful hindcasts and forecasts, dem onstrating the capabilities of the MITgcm-4DVAR system for the proposed study region. Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2021
- Source ID
- N000142112726
Entities
People
- Ganesh Gopalakrishnan
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego