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Effects of surface waves on air-sea momentum and energy fluxes and ocean response to hurricanes. Yalin Fan and Isaac Ginis GSO, University of Rhode Island. Outline. Modeling of air-sea fluxes in hurricanes Energy and momentum flux budget across air-sea interface Uniform wind Hurricanes - PowerPoint PPT Presentation
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Yalin Fan and Isaac GinisYalin Fan and Isaac Ginis
GSO, University of Rhode IslandGSO, University of Rhode Island
Effects of surface waves on air-Effects of surface waves on air-sea momentum and energy fluxes sea momentum and energy fluxes and ocean response to hurricanes and ocean response to hurricanes
1.1. Modeling of air-sea fluxes in hurricanes Modeling of air-sea fluxes in hurricanes
2.2. Energy and momentum flux budget Energy and momentum flux budget across air-sea interfaceacross air-sea interface
– Uniform wind Uniform wind
– Hurricanes Hurricanes
3.3. Wind-wave-current interaction in Wind-wave-current interaction in hurricanes hurricanes
4.4. Case study: Hurricane Ivan (2004) Case study: Hurricane Ivan (2004)
OutlineOutline
Effect of surface gravity waves on air-sea fluxes
1. Modeling of air-sea fluxes in hurricanes
c
c
c c
Ocean Currents
EFair = EFc + (EFgrowth + EFdivergence)
divergencegrowthcair
Horizontal wave propagation
(EFdivergence , )divergenceWave growth
( EFgrowth, )growth
c=air - w EFc = EFair - EFw
Momentum & energy flux
air=f((θ,k),(θ,k))
EFair=f((θ,k),(θ,k))
Air-sea flux calculations in numerical models & in this study
1. Modeling of air-sea fluxes in hurricanes1. 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 ResponseU, T, …
c
U
Atmospheric observations(wind speed, Uw )
Traditional parameterization Momentum flux ( )
Energy flux (EFair = 0)wwdairair UUC
Ocean Model
air , EFair
Coupled Wind WaveBoundary Layer Model
(Moon et al. 2004)
Wind Field
2. Energy and momentum flux budget across air-sea interface2. Energy and momentum flux budget across air-sea interface
WAVEWATCH III
Analytical spectrum model
(Hara & Belcher 2002)
Downward Energyand Momentum
Flux Budget Model
EFt
EEFEF
MFt
M
airc
airc
Wave Boundary Layer Model
Hara & Belcher (2004)
Momentum & energy flux calculations in this study
Wave Information:Wave spectra (), Hs, L,peak freq, Direction, …
growth spatial variation
M – total momentumE – total energyMF – total momentum fluxEF – total energy flux
Momentum &energy flux
air=f((θ,k),(θ,k))
EFair=f((θ,k),(θ,k))
Uniform wind experiments: Model domains
Fetch limited (space variation) experiment
Duration limited (time variation) experiment
2. Energy and momentum flux budget across air-sea interface2. Energy and momentum flux budget across air-sea interface
Steady and homogenous wind: 10, 20, 30, 40, 50 m/s
Steady and homogenous wind: 10, 20, 30, 40, 50 m/s
30o
TimeDependent
FetchDependent
Uniform Wind experiments: Momentum and energy fluxes
2. Energy and momentum flux budget across air-sea interface2. Energy and momentum flux budget across air-sea interface
|c| / |air| x 100%
|c| / |air| x 100%
EFc / EFair x 100%
EFc / EFair x 100%
= cp/u* = cp/u*
= cp/u* = cp/u*
Wind Field (m/s)
Longitude
Win
d s
pee
d (
m/s
)
0m/sTSP = 5m/s 10m/s
Lat
itu
de
Hurricane experiments
2. Energy and momentum flux budget across air-sea interface2. Energy and momentum flux budget across air-sea interface
TSP: Hurricane translation speed
10
20
3
0
40
0 9 18
Input parameters:Input parameters:Maximum wind speed (MWS)Radius of MWS (RMW)Central & environmental sea-level pressure
Holland Hurricane Wind Model
0m/sTSP = 5m/s 10m/s
TSP0m/s
TSP5m/s
Hurricane experiments
2. Energy and momentum flux budget across air-sea interface2. Energy and momentum flux budget across air-sea interface
Hs
(m)
Hs
(m)
Hs
(m)TSP
10m/s
Cg (
m/s
)C
g (m
/s)
Group Velocity
Wave Field
Hurricane experiments: Stationary Case (TSP = 0 m/s)
2. Energy and momentum flux budget across air-sea interface2. Energy and momentum flux budget across air-sea interface
|c| / |air| x 100% EFc / EFair x 100%RMW RMW
RMW RMW
Wind Speed Profile Angle between wind & wave ()
TSP = 5 m/s TSP = 10 m/s(N/m2) (N/m2)
(%) (%)
Hurricane experiments: Moving cases (TCP = 5 m/s and 10 m/s)
Longitude Longitude
Longitude Longitude
Lat
itu
de
Lat
itu
de
Lat
itu
de
Lat
itu
de
2. Energy and momentum flux budget across air-sea interface2. Energy and momentum flux budget across air-sea interface
|c| / |air| x 100% |c| / |air| x 100%
|air - c| |air - c|
EFair – EFc
EFc/EFairx100%
Hurricane experiments: Moving cases (TCP = 5 m/s and 10 m/s)
2. Energy and momentum flux budget across air-sea interface2. Energy and momentum flux budget across air-sea interface
Longitude Longitude
Longitude Longitude
Lat
itu
de
Lat
itu
de
Lat
itu
de
Lat
itu
de
TSP = 5 m/s TSP = 10 m/s
EFc/EFairx100%
EFair – EFc
air
c
3. Wind-wave-current interaction in hurricanes3. 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))
EFair=f((θ,k),(θ,k))
c
Ocean response in Control Experiment
3. Wind-wave-current interaction in hurricanes
air CurrentsW at 90 m
Ocean response in Control Experiment
3. Wind-wave-current interaction in hurricanes3. Wind-wave-current interaction in hurricanes
a b
Initial Tprofile
Sea Surface Temperature anomalyTemperature, TKE profile
RMW 2RMW
TKET TKE
T
3. Wind-wave-current interaction in hurricanes3. 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 (%
)
(%)
(%)
(%)
Differences in the Sea Surface Temperature cooling
3. Wind-wave-current interaction in hurricanes3. Wind-wave-current interaction in hurricanes
Longitude
Longitude Longitude
Longitude
A – Control B – Control
C – Control D – Control
Impact of wind-wave-current interaction on the wave fields
3. Wind-wave-current interaction in hurricanes3. Wind-wave-current interaction in hurricanes
Control & A Exp. B
Exp. C Exp. D
RMW
4. Case study: Hurricane Ivan (2004)4. Case study: Hurricane Ivan (2004) Ivan track and reconnaissance flight tracks
Flight tracks/Scanning Radar Altimeter measurementsNASA/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
3000 m
50 m
2400 m
4. Case study: Hurricane Ivan (2004)4. Case study: Hurricane Ivan (2004)Scanning Radar Altimeter (SRA) measurements
4. Case study: Hurricane Ivan (2004)4. Case study: Hurricane Ivan (2004) Hurricane research division (HRD) wind
4. Case study: Hurricane Ivan (2004)4. Case study: Hurricane Ivan (2004) Wind swath and sea surface temperature
Significant Wave Height SwathsExperiment A
Experiment B
Experiment C
Longitude
4. Case study: Hurricane Ivan (2004)4. Case study: Hurricane Ivan (2004)
4. Case study: Hurricane Ivan (2004)4. Case study: Hurricane Ivan (2004) Surface wave field & flight track
September 9 18:00 UTC
Dominant Wave Length Significant Wave Height
Wave Direction
4. Case study: Hurricane Ivan (2004)4. Case study: Hurricane Ivan (2004)
Wave parameter comparisons between model and SRA data
Left-rear Right-rear
SRA
SRA data number
SRA data number SRA data number
Vertical velocity
Main ConclusionsMain 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.
Main ConclusionsMain 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.
Thank You