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Andy Moore, Emanuele DiLorenzo, Hernan Arango, Craig Lewis, Zack Powell,

Adjoint Sensitivity Analysis of the California Current Circulation and Ecosystem using the Regional Ocean Modeling System (ROMS). Andy Moore, Emanuele DiLorenzo, Hernan Arango, Craig Lewis, Zack Powell, Arthur Miller, Bruce Cornuelle. Outline. The ROMS system The California Current

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Andy Moore, Emanuele DiLorenzo, Hernan Arango, Craig Lewis, Zack Powell,

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  1. Adjoint Sensitivity Analysis of the California Current Circulation and Ecosystem using the Regional Ocean Modeling System (ROMS) Andy Moore, Emanuele DiLorenzo, Hernan Arango, Craig Lewis, Zack Powell, Arthur Miller, Bruce Cornuelle

  2. Outline • The ROMS system • The California Current • Model configuration • Physical indices that characterize flow • Examples of sensitivities and variations • Summary

  3. The Regional Ocean Modeling System (ROMS) • Hydrostatic, Boussinesq, primitive eqn • Free surface • Terrain following coordinates • Generalized, orthogonal, curvilinear coordinates in horizontal • Open boundaries • Nesting capabilities • All parallel applications

  4. ROMS Versions • Nonlinear • Perturbation tangent linear • Finite-amplitude tangent linear • Adjoint of tangent linear myroms.org

  5. Pseudospectra Eigenmodes & Singular Value Decomposition (ARPACK-based) • Eigenmodes of • Eigenmodes of • Singular vectors: • Forcing singular vectors: • Stochastic optimals: • Hankel singular vectors:

  6. 4-Dimensional Variational Data Assimilation (4DVAR) • Strong constraint, incremental, 4DVAR - Intra-Americas Sea (myroms.org/ias) • Weak constraint, representer-based, 4DVAR

  7. Explorer of the Seas (Royal Caribbean CL)

  8. 4-Dimensional Variational Data Assimilation (4DVAR) • Strong constraint, incremental, 4DVAR - Intra-Americas Sea (myroms.org/ias) • Weak constraint, representer-based, 4DVAR

  9. Adjoint Sensitivity Analysis:Application to the California Current System

  10. High The California Current (CC) • CC circulation and biology controlled by upwelling, instability, topography • and bathymetry. • Sensitivity analysis can be used to unravel this complex system and • test hypotheses.

  11. The ROMS SCB Domain Outer domain: 20km res, 20 levels. Inner domain: 20km res, 20 levels. Derives boundary conditions from the outer domain. 20km resolution; forced by NCEP climatological winds and surface fluxes 50 years outer, 10 years inner, last 5 years considered here..

  12. JKE JSST Seasonal Circulation Index Regions April Mean SST

  13. Indices “Eady Index” An index of potential for baroclinic instability

  14. Signatures visible in time evolving adjoint fields What Physical Processes are likely to Influence J? Turbulence/ wave breaking Advection Long Rossby Waves Instability Q, P-E+R Short Rossby Waves Advection Coastally Trapped Waves & Tides

  15. Adjoint Sensitivity Analysis Forcing Adjoint ROMS

  16. Sensitivities of JSST to surface forcing

  17. Summary of Sensitivities Spring Summer Autumn Winter T T v v

  18. Summary and Conclusions • The CC coastal SST, KE and baroclinic instability exhibit pronounced seasonal variations in sensitivity to surface forcing. • Sensitivities vary by a factor ~2-4 throughout the year, but some years variations are larger (~5-10). • CC typically most sensitive during the Summer-Fall transition. • Signatures of instability processes are apparent in many of the calculations. • Significant implications for data assimilation and predictability.

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