1 Progress Towards Developing a Coupled Atmosphere-Wave-Ocean Framework for Research and Operational...
-
date post
21-Dec-2015 -
Category
Documents
-
view
217 -
download
1
Transcript of 1 Progress Towards Developing a Coupled Atmosphere-Wave-Ocean Framework for Research and Operational...
1
Progress Towards Developing a Coupled Atmosphere-Wave-Ocean Framework for
Research and Operational Hurricane Models
Isaac GinisB. Thomas, R. Yablonsky, T. Hara
University of Rhode Island
J.-W. Bao, C. Fairall, L. BiancoNOAA/ESRL
Progress Towards Developing a Coupled Atmosphere-Wave-Ocean Framework for
Research and Operational Hurricane Models
Isaac GinisB. Thomas, R. Yablonsky, T. Hara
University of Rhode Island
J.-W. Bao, C. Fairall, L. BiancoNOAA/ESRL
Interdepartmental Hurricane Conference, 2011, Miami, FL
• Hurricane model: air-sea fluxes depend on sea state (Moon et al., 2007) and sea spray (Bao et al, 2011) and include surface current
• Wave model is forced by sea state dependent wind forcing and includes surface current (Fan et al. 2009)
• Ocean model is forced by wind stress that is modified by growing or decaying wave fields (Fan et al. 2010)
Coupled Atmosphere-Wave-Ocean FrameworkCoupled Atmosphere-Wave-Ocean Framework
Red - atmospheric parameters, Green – wave parameters, Blue - ocean parameters
4
Effect of Wave Coupling on Wind Stress
Surface Roughness Drag Coefficient
Sea state dependence is parameterized based on Moon, Ginis & Hara (2007)
Wind, Waves and Drag Coefficient in the Experimental GFDL Coupled Hurricane-Wave-Ocean Model
Wind at 35 m
Drag Coeff. at 35 m
Wave phase speed
SignificantWaveheight
Wind and Current Vectors Near the Hurricane Center
Wind/current ratio is not in a proper scale
€
ru (z) −
r u (0)
u*
=1
κln
z
zo
⎛
⎝ ⎜
⎞
⎠ ⎟+ψ M
z
L
⎛
⎝ ⎜
⎞
⎠ ⎟
⎡
⎣ ⎢
⎤
⎦ ⎥
- wind speed vector at a specific height
- wind speed vector at the surface (= ocean current vector)
)(zu
€
ru (0)
Case Study: Hurricane Earl Initial Time: 00 UTC, 30 August, 2010
Effect of Ocean Current on Hurricane Intensity
Effect of Waves on Momentum Budget and Flux into Ocean
Wind stress
Wave Momentum flux
Momentum flux intoocean
€
τocean
τ air
€
τocean
€
τair
€
τwave
Momentum Flux Reduction due to Wave Coupling
Relative reduction of the momentum flux to ocean
depends on wind stress , which is not well constrained at high winds.
Uncertainty of drag coefficient
Upper bound: extrapolation of bulk parameterization
Blue: Moon et al. (2007) estimates from coupled wind-wave model
Lower bound: observations by Powell et al. (2007)
Upperbound of wind stress
Moon et al.(2007) estimate of wind stress
8% reduction
Lowerbound of wind Stress
15% reduction
€
τocean
τ air
=τ air −τ diff
τ air
€
τair
Fan et al. (2010)
Effect of Wave Momentum Budget on Hurricane IntensityCase Study: Hurricane Earl
Initial Time: 00 UTC, 30 August, 2010
Sensitivity experiments with experimentation GFDL hurricane-wave-ocean model:1.Without effect of current and wave momentum budget2. With effect of current, without effect of waves3.With effect of current, with effect of waves4.Without effect of current, with effect waves
Case Study: Hurricane Earl Initial Time: 00 UTC, 30 August, 2010
Spume production – water droplets are ripped from wave crests by the wind when surface wind exceeds about 7 ms-1.
Droplets range from ~40m to ~1mm in diameter.
Parameterization of Sea Spray EffectParameterization of Sea Spray Effect
NOAA/ESRL Sea Spray ParameterizationNOAA/ESRL Sea Spray Parameterization(Fairall et al. 2009, Bao et al. 2011)(Fairall et al. 2009, Bao et al. 2011)
Input parameters
Wave model component - WAVEWATCH III
WAVEWATCH III can accurately reproduce observed hurricane surface wave fields if:
- Wind forcing is reduced at very high wind speeds. - Ocean current is explicitly included in the simulation.
WW3 significant wave height field (color) at Sept. 15 2:00 UTC. The thick gray line is the flight track.
Significant wave height comparison between SRA measurements (during this flight) and WW3 results from experiments A, B (with modified wind stress) and C (with modified wind stress and including ocean currents).
Comparison between modeled and measured significant wave heights from all flights.
Fan et al. (2009)
Extending WW3 to Finite/Shallow Water.
* Previous version of WAVEWATCH III (v2.2.2) did not work well for water depth less than 30m (grey area below)
•New version of WAVEWATCH III (v3.1.4) includes improved physics in shallower water.
* We are validating the WAVEWATCH III (v3.1.4) results in shallower water against observations (Scanning Radar Altimeter) in collaboration with Ed Walsh.
Hurricane Ivan (2004) significant wave height predictions
WW3 2.22 WW3 3.14
Difference
Extending the model to finite/shallow water
SRA aircraft track on 3 Oct 2002 during the landfall of Hurricane Lili (from Ed Walsh)
Future Evaluation of WW3 in Shallow Waters using SRA Measurements
Summary and Future Work
• Explicit representation of wind-wave-current interaction and sea spray indicate potential important effects on the air-sea momentum fluxes in hurricane conditions.
• Some components of the developed coupled atmosphere-wave-ocean interaction framework will be implemented into the HWRF and COAMPS-TC models for testing and evaluation in 2011.