WW3 Standup Meeting Minutes

COSIMA Waves
1

Date: 29 January 2026
Attendees: @ezhilsabareesh8, @NoahDay, @sofarrell, @alberto
Chair & Minutes: @ezhilsabareesh8

1. ERA5 Forcing & Standalone WW3

  • ERA5 used as primary wind input for standalone WW3.
  • PR1 propagation scheme may be contributing to wave behaviour issues.
  • Use ERA5 neutral wind speed, which corrects for atmospheric instabilities.
  • Corrected ECMWF ERA5 dataset expected Q2 2026.

2. Wave–Current Interaction

  • Currents influence wave energy balance and redistribute energy across frequency bands.
  • Mean wave period biases may be caused by Doppler shifting from currents.
  • MOM6 current representation quality requires assessment.
  • Standalone WW3 should be tested with and without current forcing (e.g., ACCESS‑OM2 currents).

3. Excessive Low‑Frequency Dissipation

  • Too much dissipation observed in low‑frequency bands, likely from strong refraction in swell regions.
  • ST6 parameters, tuned for uncoupled WW3, may require retuning for coupled model.

4. Unresolved Obstacles Impacting Wave Biases

  • Significant wave height (Hs) biases appear near small islands and unresolved bathymetric features.
  • Dissipation parameterisation for unresolved obstacles should be explored.

5. Directional Spectra Evaluation

Directional spectra comparisons to be conducted with:

  • WHACS dataset
    CSIRO Data Access Portal
  • Southern Ocean Time Series (SOTS) directional spectra
  • NDBC deep‑water buoys (offshore stations)

6. Wave–Ice Considerations

  • Consider inclusion of ERA5 sea‑ice concentration in standalone WW3.
  • Compare attenuation behaviour for solid vs broken ice regimes.

7. Mixing & MOM6 Diagnostics

Ezhil’s tests indicate that WW3 EFACTOR improves MLD performance in MOM6 over:

  • KPP (no waves)
  • ePBL

Add the following vertical mixing diagnostics to MCW KPP runs (with and without EFACTOR):

diff_cbt_t      # vertical heat diffusivity
diff_cbt_s      # vertical salt diffusivity
diff_cbt_back   # background tracer diffusivity
diff_cbt_tides  # tidal tracer diffusivity

8. Action Items

8.1 Wave Model Evaluation (Ezhil)

  • Run standalone WW3 (ERA5 winds) and compare with:
    • WHACS
    • SOTS directional spectra
    • NDBC offshore buoys
  • Analyse PR1 propagation scheme.
  • Test WW3 with/without currents.
  • Investigate low‑frequency dissipation & refraction.
  • Evaluate WW3 wind‑correction switches.
  • Develop parameterisation for unresolved obstacles.

8.2 Data & Forcing (Ezhil)

  • Use ERA5 neutral wind speeds.
  • Assess feasibility of ERA5 sea‑ice concentration.

8.3 Wave–Ice Coupling (Noah)

  • Compare broken vs solid ice attenuation regimes.
  • Validate model against ice‑affected directional spectra.
  • Compare attenuation with CICE wave forcing
  • Evaluate fast‑ice vs broken‑ice behaviour
  • Optimise breakup scheme