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