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 1950-1995 (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 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

bbbbcbbc

bbcbbbbbcb Fpw

zKEw

zpV

z

VwVVVVgwKEV

t

KE

0

Baroclinic Conversion Term ( )bbgw

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

END

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