Title: Numerical Simulations and Observations of Surface Wave Fields Under an Extreme Tropical Cyclone
1Numerical Simulations and Observations of Surface
Wave Fields Under an Extreme Tropical Cyclone
- Yalin Fan
- Isaac Ginis
- University of Rhode Island
Collaborators Tetsu Hara (URI), Wayne Wright
(NASA), Edward Walsh (NASA)
2Wind-Wave-Current Interaction in Tropical Cyclones
Wind
Wave information
Atmosphere
Current
Surface waves
Ocean
Current
Ocean currents
3Observations under hurricane Ivan
Envisat-1 ERS-2
4Experiments
Exp.
A
B
C
Exp. A WAVEWATCH III wave model (operational
model) Exp. B Coupled wind-wave model (accounts
for sea state) Exp. C Coupled wind-wave-current
model
WAVEWATCH III
Wave Bounary Layer Model
Princeton Ocean Model
Wind
Atmosphere
Wave information
Current
Surface waves
Ocean
Current
Ocean currents
5Wave Predictions
- Significant Wave Height Swaths
Exp. A
Exp B
Exp C
Exp A - Exp C
Exp. A WAVEWATCH III wave model (operational
model) Exp. B Coupled wind-wave model (accounts
for sea state) Exp. C Coupled wind-wave-current
model
6Wave Predictions
- Wave parameter comparisons between model and
SRA data
Vertical velocity
Sept. 9
Wave Direction
SRA
SRA data number
Dominant Wave Length
Significant Wave Height
SRA data number
SRA data number
7Wave Predictions
- Wave parameter comparisons between model and
SRA data
- Sept. 9 - Sept. 12 - Sept.
14-15
Exp. A
Exp. B
Exp. C
Model Hs (m)
SRA Hs (m)
SRA Hs (m) SRA Hs (m)
8Wave Predictions
- Comparison with Satellite measurements (Exp. C)
Sept. 15 200 UTC
Envisat-1 Sept. 15, 338 UTC
ERS-2 Sept. 15, 406 UTC
Sept. 15 400 UTC
Sept. 14 2200 UTC
SRA
9Wave Predictions
- Comparison with NDBC Buoy measurements
10Wave Predictions
- Current Effect on Wave Prediction
Wave Action Equation
N ?/? ------ wave action spectrum, Cg
------ group velocity vector, ------
wave number vector, k ------ wave number, ?
------ wave direction, s ------ a coordinate in
the wave direction, m ------ coordinate
perpendicular to s, F ------ forcing,
------ ocean current
Exp D
11Wave Predictions
- Reduction of significant wave height by current
Hs difference (Exp C -Exp D)
Wave Field
Sept. 9
Hs difference (Exp D -Exp B)
Current Field
Exp C Exp D
C - D
12Main Conclusions
- The original WAVEWATCH III drag parameterization
tends to overestimate the significant wave
height, and wave energy under very strong wind
forcing. - The improved stress parameterization, together
with including the wave-current interaction, is
shown to improve forecast of significant wave
height and wave energy. - 3. The hurricane induced ocean current tends to
reduce the significant wave height mainly because
it increases the advection speed of the wave
packet. The strong shear of the current field
widens the directional spreading of the wave
spectrum.
13Acknowledgement U.S. National Science
Foundation. U.S. Office of Naval Research
(CBLAST program). NASA - Physical Oceanography
Program NOAA - Hurricane Research Division
Thank You !