1. Yalin Fan and Isaac Ginis GSO, University of Rhode Island Effects of surface waves on air- sea momentum and energy fluxes and ocean response to hurricanes

2. 1.Modeling of air-sea fluxes in hurricanes 2.Energy and momentum flux budget across air-sea interface –Uniform wind –Hurricanes 3.Wind-wave-current interaction in hurricanes 4.Case study: Hurricane Ivan (2004) Outline

3.  Effect of surface gravity waves on air-sea fluxes 1. Modeling of air-sea fluxes in hurricanes c c cc Ocean Currents EF air = EF c + (EF growth + EF divergence ) Horizontal wave propagation (EF divergence, ) Wave growth ( EF growth, )

4.  c =  air -  w EF c = EF air - EF w Momentum & energy flux  air =f(  (θ,k),  (θ,k)) EF air =f(  (θ,k),  (θ,k))  Air-sea flux calculations in numerical models & in this study 1. Modeling of air-sea fluxes in hurricanes Wave information  (θ,k), Hs, L, T, … Downward Energy and Momentum Flux Budget Model Princeton Ocean Model (POM) Ocean Response U, T, … U Atmospheric observations (wind speed, U w ) Traditional parameterization Momentum flux ( ) Energy flux (EF air = 0) Ocean Model, EF air Coupled Wind Wave Boundary Layer Model (Moon et al. 2004) Wind Field

5. 2. Energy and momentum flux budget across air-sea interface WAVEWATCH III Analytical spectrum model (Hara & Belcher 2002) Downward Energy and Momentum Flux Budget Model Wave Boundary Layer Model Hara & Belcher (2004) Momentum & energy flux calculations in this study Wave Information: Wave spectra (  ), Hs, L, peak freq, Direction, … growthspatial variation M – total momentum E – total energy MF – total momentum flux EF – total energy flux Momentum &energy flux  air =f(  (θ,k),  (θ,k)) EF air =f(  (θ,k),  (θ,k))

6.  Uniform wind experiments: Model domains Fetch limited (space variation) experiment Duration limited (time variation) experiment 2. Energy and momentum flux budget across air-sea interface Steady and homogenous wind: 10, 20, 30, 40, 50 m/s 30 o

7. Time Dependent Fetch Dependent  Uniform Wind experiments: Momentum and energy fluxes 2. Energy and momentum flux budget across air-sea interface |  c | / |  air | x 100% EF c / EF air x 100% = c p /u *

8. Wind Field (m/s) Longitude Wind speed (m/s) 0m/s TSP = 5m/s 10m/s Latitude  Hurricane experiments 2. Energy and momentum flux budget across air-sea interface TSP: Hurricane translation speed 10 20 30 40 0 9 18 Input parameters: Maximum wind speed (MWS) Radius of MWS (RMW) Central & environmental sea-level pressure Holland Hurricane Wind Model

9. 0m/s TSP = 5m/s 10m/s TSP 0m/s TSP 5m/s  Hurricane experiments 2. Energy and momentum flux budget across air-sea interface Hs (m) TSP 10m/s C g (m/s) Group Velocity Wave Field

10.  Hurricane experiments: Stationary Case (TSP = 0 m/s) 2. Energy and momentum flux budget across air-sea interface |  c | / |  air | x 100% EF c / EF air x 100% RMW Wind Speed Profile Angle between wind & wave (  )

11. TSP = 5 m/sTSP = 10 m/s (N/m 2 ) (%)  Hurricane experiments: Moving cases (TCP = 5 m/s and 10 m/s) Longitude Latitude 2. Energy and momentum flux budget across air-sea interface |  c | / |  air | x 100% |  air -  c |

12. EF air – EF c EF c /EF air x100%  Hurricane experiments: Moving cases (TCP = 5 m/s and 10 m/s) 2. Energy and momentum flux budget across air-sea interface Longitude Latitude TSP = 5 m/sTSP = 10 m/s EF c /EF air x100% EF air – EF c

13. 3. Wind-wave-current interaction in hurricanes Control ( one-way interaction, fluxes from air ) Exp. A ( one-way interaction, fluxes into currents ) Exp. B ( two-way interaction, partial ) Exp. D ( fully coupled ) Exp. C ( two-way interaction, partial ) Momentum & energy flux  air =f(  (θ,k),  (θ,k)) EF air =f(  (θ,k),  (θ,k))

14.  Ocean response in Control Experiment 3. Wind-wave-current interaction in hurricanes  air Currents W at 90 m

15.  Ocean response in Control Experiment 3. Wind-wave-current interaction in hurricanes ab Initial T profile Sea Surface Temperature anomaly Temperature, TKE profile RMW2RMW TKE T T

16. 3. Wind-wave-current interaction in hurricanes  Momentum Flux ratio  c in A /  air in Control  air in B /  air in Control  air in C /  air in Control  c in D /  air in Control (%)

17.  Differences in the Sea Surface Temperature cooling 3. Wind-wave-current interaction in hurricanes Longitude A – Control B – Control C – ControlD – Control

18.  Impact of wind-wave-current interaction on the wave fields 3. Wind-wave-current interaction in hurricanes Control & AExp. B Exp. CExp. D RMW

19. 4. Case study: Hurricane Ivan (2004)  Ivan track and reconnaissance flight tracks Flight tracks/Scanning Radar Altimeter measurements NASA/Goddard spacing flight center & NOAA/HRD Exp. A: WAVEWATCH III wave model (operational model) Exp. B: Coupled wind-wave model Exp. C: Coupled wind-wave-current model

20. 3000 m 50 m 2400 m 4. Case study: Hurricane Ivan (2004)  Scanning Radar Altimeter (SRA) measurements

21. 4. Case study: Hurricane Ivan (2004)  Hurricane research division (HRD) wind

22. 4. Case study: Hurricane Ivan (2004)  Wind swath and sea surface temperature

23.  Significant Wave Height Swaths Experiment A Experiment B Experiment C Longitude 4. Case study: Hurricane Ivan (2004)

24.  Surface wave field & flight track September 9 18:00 UTC

25. Dominant Wave Length Significant Wave Height Wave Direction 4. Case study: Hurricane Ivan (2004)  Wave parameter comparisons between model and SRA data Left-rear Right-rear SRA SRA data number Vertical velocity

26. Main Conclusions Uniform Wind Study: For momentum flux calculations at the air-sea interface, the effect of time variation of the wave field is small but the effect of spatial variation is important. Both effects, however, are important for energy flux calculations. The energy flux into currents depends on both wave age and friction velocity, and is roughly proportional to the 3.5th power of the friction velocity, rather than the 3rd power previously suggested by the literature.

27. Main Conclusions Hurricane Study: The surface wave effects on the air-sea fluxes are most significant in the rear-right quadrant of the hurricane and consequently reduce the magnitude of subsurface currents and sea surface temperature cooling to the right of the storm track. Wave-current interaction reduces the momentum flux into currents mainly due to the reduction of wind speed input into the wave model relative to the ocean currents. The improved momentum flux parameterization, together with wave-current interaction is shown to improve forecast of significant wave height and wave energy in Hurricane Ivan.

28. Thank You