Shuyi S. ChenJoseph Tenerelli, Wei Zhao, Mark Donelan
Rosenstiel School of Marine and Atmospheric ScienceUniversity of Miami
Coupled Atmosphere-Wave-Ocean Parameterizations for High-Winds
Sponsored by the Office of Naval Research
AMS 13th Conf on Interactions of the Sea and Atmos., Portland, 9-13 August 2004
ATMOS. MODEL
(MM5/COAMPS/WRF)
OCEAN MODEL
(HYCOM or 3DUOM)
WAVE MODEL
(WAVEWATCH III or WAM)
Roughness length
Wind-induced stress
Surface fluxes and stress
SST
SSH
& c
urre
nt v
eloc
ityW
ave-
Indu
ced
stre
ss
Coupled Atmosphere-Wave-Ocean Modeling System for Hurricane Predictions
LESSea
Spray
Param. of spectral tail and drag coefficient
Param. of wave
dissipation
Source function?Drop size distribution?Effects on turbulence?
How do these affect exchange coefficients of enthalphy? What is the ratio of CK and CD?
LKB (1979)
What is the ratio of CK and CD?
• MM5 (PSU/NCAR)(vortex-following nests with 45, 15, 5, and 1.67 km grid spacing, NCEP analysis and AVHRR or TMI/AMSR-E SST)
• WAVEWATCH III (NOAA/EMC)
(1/12o, 25 frequency bands, 48 directional frequency bands)
• HYCOM (UMiami/NRL)(1/12o, 22 vertical levels with 4-6 in the ocean mixed layer)
• 3DUOM (Price’s 3-D Upper Ocean Circulation Models)
Coupled Modeling System
• Model initialized on 00 UTC 11 Sep 1999 using the AVN analysis fields and the AVHRR Pathfinder SST
• 30 vertical levels, lowest half-sigma level about 12 m above the surface
• Four levels of nests, with grid spacing of 45, 15, 5, and 1.6 km, all but the coarsest mesh moving with the hurricane
• Modified surface flux parameterization based on Garratt (1992) and Pagowski and Moore (2000)
MM5 Configuration
WAVEWATCH III Configuration
• 4-D Spectrum Model [(x, y), (k, • 1/6 degree grid spacing
• 25 frequency bands (logarithmically spaced from 0.04-0.4 Hz)
• 48 directional frequency bands (evenly spaced by 7.5o)
Hybrid Coordinate Ocean Model (HYCOM)
• one-way nested Western Atlantic-Gulf of Mexico-Caribbean Sea regional domain (with data assimilation of SSH prior to hurricane simulations)
• 1/12 degree grid spacing• 22 Vertical layer, 4-6 layers in mixed layer with the
1st layer at 3 meter • MM5 atmospheric forcing, 8 September – 17
October 2002 (Hurricanes Isidore and Lili)
WW3Observed
Open Ocean (Northeast)
WW3Observed
Landfall (Southwest)
• Roughness Length (non-directional)
= tw zo
zo - wave-age dependent
• Stress Vector (directional)
Mx = - x
My = - y
x , y - components of stress from integral of
momentum input to the wave spectrum.
Coupled MM5-WAVEWATCH III
V
Wind-Wave Coupling
Spectra Tail Parameterization:
X-component of stress from integral of momentum input to the spectrum:
Growth rate of each component from measurement of pressure-slope correlation Spectrum of long waves from WAVEWATCH III; spectrum of short waves from fit to tail given below. is adjusted to fit the highest modeled wavenumbers.
is the spreading function for the short waves.
kdkdkkFg xw
ax ),(
0
1)(
cos.1
)(
cos28.0 )/()/(
kC
U
kC
U kk
w
a
))((sec),( 25khkkF
9.0/;)/(cos
2.11
UCUC
Figure 4. Vorticity contours obtained via Digital Particle Image Velocimetry (DPIV) in the air flow over wind driven waves [Reul, 1998]. Both wave and air flow are from left to right. (Top) waves of gentle slope – non-separated flow. (Bottom) waves of steep slope – separated flow.
Z(cm)
0 10 20 30 40 x (cm)
0
0
6
6
Drag coefficient in high-wind conditions (Donelan et al. 2004)
Hurricane Floyd (1999)
• Emanuel (1995) found that Ck/Cd > 1 for intensifying storms.• CBLAST observed Ck/Cd < 1 (C. Fairall).
Uncoupled Ck/Cd Coupled Ck/Cd
Before Bonnie
After Bonnie... .
..
...
Net Heat Flux
Uncoupled
Coupled Ocean
Coupled Wave-Ocean
Temperature Profiles
Open Ocean Gulf Stream
Hurricanes Isidore and Lili (2002) in tandem
Hurricane Lili (2002)
SST BeforeIsidore
HYCOM
Satellite
HYCOM
Satellite
SST Cooling After Isidore
HYCOM
Satellite
SST Cooling After Lili
Loop CurrentGulf Common Water
Isidore Lili Isidore Lili
CBLAST-Hurricane Coupled Atmosphere-Wave-Ocean Modeling
Atmosphere-Ocean coupling improves tropical cyclone intensity forecasts, especially at very high resolution when eyewalls are explicitly resolved.
Wind-Wave coupling contributes to storm asymmetry that very significantly from storm-to-storm.
Simple 3DUOM+Satellite SST works well over the open ocean. However, full ocean model, e.g. HYCOM, is needed for the coastal regions and over the Gulf Stream and warm eddies.
Conclusions