OC4331-Mesoscale Oceanography
Final Project Summary

Topic Area

LT Charles L Williams, USN

The history of Optimum Thermal Interpolation System (OTIS) started in 1975 with the Ocean Thermal Structure (OTS) analysis. This was a 3D tool for the Northern Hemisphere. Through many upgrades and improvements OTS evolved into OTIS 4.0. As of 1997 OTIS had regional 3D, global 3D and global high resolution sea surface temperature (SST) outputs. The drawback to OTIS was that it was a univariant model using Temperature relationships to derive all other variables. OTIS also created 3D outputs by layering 2D model outputs on top of each other to create a slice version that could then be interpolated to get a 3d output. Although this method had value, it always required a human input, commonly referred to as the “Bogus”, to ensure a realistic interpretation of currents and eddies.

A useful tool currently used throughout the fleet is the Modular Ocean Data Assimilation System (MODAS). MODAS is also a univariant model. This system is essentially a modular OTIS that is able to be used real-time for operational purposes.

The next generation in the evolution of OTIS is Navy Coupled Ocean Data Assimilation (NCODA). Although Navy Coupled Ocean Data Assimilation (NCODA) and Optimum Thermal Interpolation System (OTIS) are both derived from the Optimum Interpolation technique, NCODA incorporates several improvements over OTIS. The rest of this document will focus on the NCODA's improvements.

NCODA was funded as part of a study to improve COAMPS by further coupling it to the sea. It is not a univariant model and uses temperature, salinity, geopotential and currents as inputs. NCODA is the closest ocean modeling has come to resemble numerical weather prediction (NWP). Like NWP, NCODA uses primitive equations to create the model output. NCODA also has a data assimilation cycle that is similar to NWP, using satellites, XBT’s, buoys, and submarines as inputs. Since submarines operate similar to airplane, the best way to explain submarine inputs are to compare them to PIREPS from planes.

With the improved accuracy and precision of NCODA, the need for a “Bogus” has been eliminated. The only thing a “Bogus” is now used in quality control or postprocessing. Also with the use of primitive equations, 3D is no longer done by slices, but the same as NWP.

As NCODA improves, it is likely to be integrated into COAMPS as the Seas portion, replace the currently used MODAS, or become another model with specific outputs available from FNMOC.

The most important aspects of NCODA include:

1) NCODA is similar to NWP models:

• Incorporates Satellite data
• Uses the Primitive Equations for the Ocean
• Incorporates Submarine data (similar to PIREP’s in NWP)

2) NCODA is likely the next generation Ocean Model which could:

• Be incorporated into COAMPS as the sea portion of the model
• Replace MODAS as the model used by the operators
• Become a model similar to NOGAPS and COAMPS with specific outputs on FNMOC website

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Clancy,R. and W. Sadler, 1992: "The Fleet Numerical Oceanography Center Suite of Oceanographic Models and Products." Weather and Forecasting., Vol. 7, No. 2, 2289-2297.

Cummings, J.A., C. Szezechowski and M. Carnes, 1997: "Global and regional ocean thermal analysis systems" MTS Journal, Vol. 31 (1), 63-75.

Interview with James A. Cummings, at NRL Monterey, CA, November 2006.

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