Ocean Instabilities Captured By Breeding On A Global Ocean Model Matthew Hoffman, Eugenia Kalnay, James Carton, and Shu-Chih Yang
Quick Overview of Breeding Developed by Toth and Kalnay (1993, 1997) to estimate the shape of growing errors in a non-linear atmospheric model The parameters can be tuned to isolate instabilities of different time scales Yang et al. (2005) used breeding on a coupled GCM to identify slow growing ENSO modes
Our Model GFDL Modular Ocean Model (MOM) Driven by monthly averaged winds from (same data set as used by Carton et al. in a 2000 reanalysis) Stretched grid in vertical and in latitude with highest resolution at the equator and in upper ocean
The Breeding Process A small, random perturbation is added to the initial state of the system Both the perturbed and unperturbed (control) conditions are integrated forward in time The control forecast is subtracted from the perturbed forecast, yielding the bred vector The bred vector is rescaled to it’s initial size and added to the control forecast as a new perturbation
10-Day Bred Vectors
Pacific TIWs at 3.5°N
30-Day Bred Vector 10-Day Bred Vector 30-Day Breeding vs. 10-Day Breeding
30-Day Bred Vector 10-Day Bred Vector
Bred Vector Kinetic Energy Advection of KE Baroclinic energy conversion Barotropic energy conversion
Baroclinic Conversion Term ( )
Vertically and Monthly Averaged Baroclinic Conversion
Vertically and Monthly Averaged Barotropic Conversion
Baroclinic at 3.375°N Barotropic at 0.65°N Vertical Profiles of Monthly Averaged Energy Terms
Breeding can isolate instabilities of different time scales in a full ocean model. The bred vector energy equations show location, shape, and sign of energy conversion. This has been shown to work in the Atlantic and Indian Ocean as well. We plan on performing a more complete analysis of mid-latitude instabilities. Conclusions and Future Work
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Initial Bred Vector
Tropical Instability Waves 10-day breeding time From January 1988 to December 1989 Equatorial Cold Tongue Background SST is shaded Bred Vectors are shown in contour