Improving air-sea flux parameterization in the GFDL/URI Coupled Hurricane-Wave-Ocean

Model for Transition to Operations

Isaac Ginis

Il Ju Moon, Tetsu Hara, Biju Thomas

University of Rhode Island

and

Morris Bender

NOAA/GFDL

Collaborations: H. Tolman (EMC/NCEP)E. Walsh (ETL/NOAA)S. Belcher (UR, UK)

Drag and Heat Exchange Coefficients vs Wind Drag and Heat Exchange Coefficients vs Wind Speed in the GFDL Operational ModelSpeed in the GFDL Operational Model

CdCd

ChCh

•Based on simple bulk Based on simple bulk parameterization. parameterization.

•States of growth of States of growth of wind waves relative to wind waves relative to local wind forcing is local wind forcing is neglected.neglected.

0185.0~.2*

0 constu

gz

• Near the peak : Near the peak : NCEPNCEP WAVEWATCH III wave modelWAVEWATCH III wave model..• High frequency part : High frequency part : Equilibrium spectrum modelEquilibrium spectrum model of Hara and of Hara and

Belcher (2002)Belcher (2002)

maxk0k

2k

1k

mink

1k

3k

2k 0k

012325 - max-1

vk

High frequency partNear peak

Coupled Wave-Wind (CWW) ModelCoupled Wave-Wind (CWW) Model

Wave Boundary Layer ModelWave Boundary Layer Model

Two dimensional wave spectrum:Two dimensional wave spectrum:

Wind profile and drag coefficientWind profile and drag coefficientover any given seasover any given seas

Explicitly calculates wave-induced stress

Full wave spectrum

Wave-Wind Simulations in Real Hurricanes Wave-Wind Simulations in Real Hurricanes

20 30 50

U10 (m /s)40

0

Powell et al. (2003) Large & Pond (1981)W W 3 (upper and lower bound)

3

1

Our results (upper and lower bound)

5

4

2C

D *

100

0

Bulk, 0.0185

• At high wind speeds, CAt high wind speeds, Cdd

levels off and even decrease levels off and even decrease with wind speedwith wind speed

• Under hurricane wind forcing Under hurricane wind forcing waves arewaves are extremely youngextremely young at at high wind speeds and the high wind speeds and the young waves produceyoung waves produce small small dragdrag..

Cd estimated from Cd estimated from CWW modelCWW modelhurricane simulationshurricane simulations

Upper and lower bounds from CWW model

GPS sonde observation under various GPS sonde observation under various hurricanes (Powell et al., 2003). hurricanes (Powell et al., 2003).

WAVEWATCH III

GFDL(WRF)Hurricane Model

NCEPWAVEWATCH III

Flux

Wind &Air Temp.

Atmosphere

Ocean Waves

Currents,

Wave Boundary Model

SST

Wave Spectra

Flux

POM(HYCOM)

Wind &Air Temp.

Flux

GFDLHurricane Model

POM

SST &Current

SST

Flux

Atmosphere

Ocean

Elevations, & SST

Operational GFDL/URI ModelOperational GFDL/URI Model Coupled Hurricane-Wave-Ocean ModelCoupled Hurricane-Wave-Ocean Model

Hurricane Ivan, Initial time: 00Z 12 SepHurricane Ivan, Initial time: 00Z 12 Sep

Hurricane Ivan, Initial time: 00Z 12 SepHurricane Ivan, Initial time: 00Z 12 Sep

880 900 920 940 960 980 1000 1020M inim um Sea Level P ressure (hPa)

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

Max

imum

Sur

face

Win

ds (

m/s

)P ressu re -W in d R e la tio n sh ip fo r Iv an

W ave-coupled

Uncoupled

Standard Relationship for Atlantic

• We have developed We have developed aa coupled hurricane-wave-oceancoupled hurricane-wave-ocean by by coupling the GFDL/URI hurricane-ocean model with the coupling the GFDL/URI hurricane-ocean model with the NCEP WAVEWATCH III wave model and a wave boundary NCEP WAVEWATCH III wave model and a wave boundary layer model.layer model.

• Preliminary Preliminary simulations indicate that the hurricane intensity simulations indicate that the hurricane intensity and structure can be significantly effected by explicit and structure can be significantly effected by explicit simulations of surface waves.simulations of surface waves.

• More rMore real-case simulations will be done in the nearest eal-case simulations will be done in the nearest future to assess the impact of wave coupling on hurricane future to assess the impact of wave coupling on hurricane predictions.predictions.

• Future work will be directed toward improving the heat flux Future work will be directed toward improving the heat flux parameterization in the coupled model and transitioning to parameterization in the coupled model and transitioning to the Hurricane WRF. the Hurricane WRF.

SummarySummary