1. 1 Progress Towards Developing a Coupled Atmosphere-Wave-Ocean Framework for Research and Operational Hurricane Models Isaac Ginis B. Thomas, R. Yablonsky, T. Hara University of Rhode Island J.-W. Bao, C. Fairall, L. Bianco NOAA/ESRL Interdepartmental Hurricane Conference, 2011, Miami, FL

2. Wind-Wave-Current Interaction Image courtesy of Fabrice Veron

3. Hurricane model: air-sea fluxes depend on sea state (Moon et al., 2007) and sea spray (Bao et al, 2011) and include surface current Wave model is forced by sea state dependent wind forcing and includes surface current (Fan et al. 2009) Ocean model is forced by wind stress that is modified by growing or decaying wave fields (Fan et al. 2010) Coupled Atmosphere-Wave-Ocean Framework Red - atmospheric parameters, Green – wave parameters, Blue - ocean parameters

4. 4 Effect of Wave Coupling on Wind Stress Surface RoughnessDrag Coefficient Sea state dependence is parameterized based on Moon, Ginis & Hara (2007)

5. Wind, Waves and Drag Coefficient in the Experimental GFDL Coupled Hurricane-Wave-Ocean Model Wind at 35 m Drag Coeff. at 35 m Wave phase speed Significant Wave height

6. Wind and Current Vectors Near the Hurricane Center Wind/current ratio is not in a proper scale - wind speed vector at a specific height - wind speed vector at the surface (= ocean current vector)

7. Effect of Ocean Current on Wind Stress U * vs. Wind Speed at 35 m

8. Case Study: Hurricane Earl Initial Time: 00 UTC, 30 August, 2010 Effect of Ocean Current on Hurricane Intensity

9. Effect of Waves on Momentum Budget and Flux into Ocean Wind stress Wave Momentum flux Momentum flux into ocean

10. Momentum Flux Reduction due to Wave Coupling Relative reduction of the momentum flux to ocean depends on wind stress, which is not well constrained at high winds. Uncertainty of drag coefficient Upper bound: extrapolation of bulk parameterization Blue: Moon et al. (2007) estimates from coupled wind-wave model Lower bound: observations by Powell et al. (2007) Upper bound of wind stress Moon et al.(2007) estimate of wind stress 8% reduction Lower bound of wind Stress 15% reduction Fan et al. (2010)

11. Effect of Wave Momentum Budget on Hurricane Intensity Case Study: Hurricane Earl Initial Time: 00 UTC, 30 August, 2010

12. Sensitivity experiments with experimentation GFDL hurricane-wave-ocean model: 1.Without effect of current and wave momentum budget 2. With effect of current, without effect of waves 3.With effect of current, with effect of waves 4.Without effect of current, with effect waves Case Study: Hurricane Earl Initial Time: 00 UTC, 30 August, 2010

13. Spume production – water droplets are ripped from wave crests by the wind when surface wind exceeds about 7 ms -1. Droplets range from ~40  m to ~1mm in diameter. Parameterization of Sea Spray Effect

14. NOAA/ESRL Sea Spray Parameterization (Fairall et al. 2009, Bao et al. 2011) Input parameters

15. Effect of Sea Spray on Momentum Flux

16. Sea Spray Effect on Drag Coefficient

17. Wave model component - WAVEWATCH III WAVEWATCH III can accurately reproduce observed hurricane surface wave fields if: - Wind forcing is reduced at very high wind speeds. - Ocean current is explicitly included in the simulation. WW3 significant wave height field (color) at Sept. 15 2:00 UTC. The thick gray line is the flight track. Significant wave height comparison between SRA measurements (during this flight) and WW3 results from experiments A, B (with modified wind stress) and C (with modified wind stress and including ocean currents). Comparison between modeled and measured significant wave heights from all flights. Fan et al. (2009)

18. Extending WW3 to Finite/Shallow Water. * Previous version of WAVEWATCH III (v2.2.2) did not work well for water depth less than 30m (grey area below) New version of WAVEWATCH III (v3.1.4) includes improved physics in shallower water. * We are validating the WAVEWATCH III (v3.1.4) results in shallower water against observations (Scanning Radar Altimeter) in collaboration with Ed Walsh.

19. Hurricane Ivan (2004) significant wave height predictions WW3 2.22WW3 3.14 Difference Extending the model to finite/shallow water

20. SRA aircraft track on 3 Oct 2002 during the landfall of Hurricane Lili (from Ed Walsh) Future Evaluation of WW3 in Shallow Waters using SRA Measurements

21. Summary and Future Work Explicit representation of wind-wave-current interaction and sea spray indicate potential important effects on the air-sea momentum fluxes in hurricane conditions. Some components of the developed coupled atmosphere-wave-ocean interaction framework will be implemented into the HWRF and COAMPS-TC models for testing and evaluation in 2011.