Developing Coupled Tropical Cyclone-Wave-Ocean Models for Transition to Operations Isaac Ginis Yalin Fan, Richard Yablonsky, Biju Thomas Graduate School of Oceanography University of Rhode Island Morris Bender Geophysical Fluid Dynamics Laboratory,

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Developing Coupled Tropical
Cyclone-Wave-Ocean Models for Transition to
OperationsIsaac GinisYalin Fan, Richard
Yablonsky, Biju ThomasGraduate School of
OceanographyUniversity of Rhode IslandMorris
BenderGeophysical Fluid Dynamics Laboratory,
NOAA63th Interdepartmental Hurricane
Conference
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Coupled Hurricane-Ocean Models Transitioned to
Operations

• 2001 GFDL/POM at NCEP in the Atlantic basin (3D
  coupling) and Eastern and Central Pacific (1D
  coupling).
• 2007 HWRF/POM at NCEP in the Atlantic basin (3D
  coupling).
• 2008 GFDN/POM at FNMOC in the Atlantic basin
  (3D coupling) and all other ocean basins (1D
  coupling)
• 2009 GFDN/POM at FNMOC 3D coupling in the
  Northern Pacific.

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Todays Discussion

• What are the differences between 3D and 1D ocean
  coupling for hurricane forecasts?
• Impact of warm ocean eddys circulation on
  hurricane-induced cooling and its implication
  for hurricane intensity.
• Test experiments with a new coupled
  hurricane-wave-ocean framework.

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Ocean response to hurricane forcing 1. Vertical
mixing/entrainment
A T M O S P H E R E
Wind stress ? surface layer currents
Current shear ? turbulence
Turbulent mixing ? entrainment of cooler water
O C E A N
Warm sea surface temperature
Sea surface temperature decreases
Cool subsurface temperature
Subsurface temperature increases
This is a 1-D (vertical) process
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Ocean response to hurricane forcing 2. Upwelling
A T M O S P H E R E
Cyclonic wind stress ? divergent surface currents
Divergent currents ? upwelling
Upwelling ? cooler water brought to surface
O C E A N
Warm sea surface temperature
Cool subsurface temperature
This is a 3-D process
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SST cooling within hurricane inner-core in 3D
and 1D ocean models
Hurricanes have historically translated in the
Gulf of Mexico lt 5 m s-1 73 and lt 2 m s-1 16
of the time in the western tropical North
Atlantic at lt 5 m s-1 62 and lt 2 m s-1 12 of
the time
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Temperature vertical cross-section in 3D and 1D
ocean models
Speed 2.5 m s-1
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Warm-core ring is not just high ocean heat content
Since warm water is deep in the ring, WCRs
generally restrict hurricane-induced SST cooling
But can a WCRs circulation modify hurricane-core
SST cooling via advection?
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A T M O S P H E R E
Prescribed translation speed
Cyclonic hurricane vortex
lt
lt
lt
lt
O C E A N
lt
lt
lt
lt
Homogeneous initial SST
Vary position of ring relative to storm track
lt
lt
lt
lt
Horizontally-homogeneous subsurface temperature
Warm core ring evident in subsurface temperature
field
WCRL
WCRR
CTRL
WCRC
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SST and Surface Currents in 4 idealized
experiments
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Differences in SST cooling within hurricane
inner-core with and without WCR
The presence of a warm core eddy in advance of a
hurricane may in some cases create a less
favorable condition for hurricane intensification
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Conventional Coupling Between Hurricane and Ocean
Models
Hurricane Model
Momentum flux (t) Sensible heat flux (QH) Latent
heat flux (QE) Momentum flux (t)
Wind speed (Ua) Temperature (Ta) Humidity
(qa) Surface current (Us) SST (Ts)
Air-Sea Interface
Ocean Model
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Atmospheric Boundary Layer
Momentum KE Flux
Heat Humidity Flux
Turbulence
Sea Spray
Wave induced stress? Reynolds stress ?
Airflow separation Intermittency
Air-Sea Interface
Nonbreaking Waves
Breaking Waves
Stokes drift
Bubbles
Momentum KE Flux
Intermittency of Momentum KE injection
(Langmuir) Turbulence
Ocean Boundary Layer
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Coupled Hurricane-Wave-Ocean Framework

• Implemented in GFDL model in research mode.
• To be implemented in HWRF later this year

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Sea State Dependence of Surface Parameters
Surface Roughness
Drag Coefficient
Based on the coupled GFDL hurricane-wave-ocean
coupled model simulations
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Hurricane Rita simulation Initial time Sept.
20, 2005 12Z
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Hurricane Rita simulation Initial time Sept.
20, 2005 12Z
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Improved track forecasts of Hurricane Rita with
inclusion of wave coupling
Sept. 19 00Z
Sept. 20 12Z
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Little improvement in intensity forecasts of
Hurricane Rita with inclusion of wave coupling
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Summary

• 1D ocean models have significant limitations for
  coupled hurricane-ocean forecasting, particularly
  for slower moving storms and over mesoscale ocean
  features.
• Initial test experiments with the newly developed
  coupled hurricane-wave-ocean framework show
  promises for improving hurricane forecast skill.
• Sea spray effects are being included in
  collaboration with C. Fairall and J.-W. Bao
  (ESRL).
• Future plans include implementation of the new
  air-sea interaction framework into GFDN and HWRF
  models.