Regional AirSea Interactions in Eastern Pacific

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Regional Air-Sea Interactions in Eastern Pacific
Hyodae Seo Scripps Institution of Oceanography

• 6th International RSM Workshop
• Palisades, New York
• July 11-15, 2005

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Outline

• 1. Regional Ocean Atmosphere Coupled Model
• 2. Research
• 1. Gap-Induced Low-Level Winds and Air-Sea
  Interaction in Central America
• 2. Atmospheric Boundary Layer Adjustment to
  Tropical Instability Waves (TIWs) in Eastern
  Tropical Pacific
• 3. Summary

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Regional Ocean-Atmosphere Coupled Model
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1. Model and Coupler Description
Regional Ocean-Atmosphere Coupled Model

• Bulk Formula in BL

Atmosphere

• Winds Relative to Ocean

Ocean
Boundary Layer Variables
Regional Spectral Model (RSM)
COARE Bulk Formula Plus Winds relative to ocean
currents
Regional Ocean Modeling System (ROMS)

• Sequential Coupling
• Coupling Frequency
• ? 3 hourly coupling
• ? Daily coupling

SST
Lateral BC Ocean Data Assimilation
Product (JPL)
IC and Lateral BC NCEP/DOE Reanalysis
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Gap-Induced Low-level Winds and Air-Sea
Interaction in Central America
OBSERVATION Xie et al., 2005 Jan-Mar SST and
Windstress Climatology
Tehuantepec
Papagayo
Panama
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2.1. Gap Winds and Air-Sea Interaction
1999-2003 Model Climatology
Sea Surface Temperature (C)
Ekman Pumping Velocity (10-6 m/s)
Precipitation (mm/day)
Winter
Winter
Winter
Tehuantepec
Papagayo
Panama
Costa Rica Dome
Upwelling by Papagayo Jet
Summer
Summer
Summer
Cold SST
Dry Hole
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Atmospheric Boundary Layer Response to Tropical
Instability Waves (TIWs) in Eastern Tropical
Pacific
Global SST Image from microwave satellites Aug
25-27, 1999 (Wentz et al.)
Tropical Instability Waves (TIWs)
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2.2 Atmospheric BL Adjustment to SSTsa. Winds
and SST
June 21 October 20 1999
OBSERVED SSTs
MODEL SST

• 3 month average of wind-stress and SST
• Similar gross
• patterns of winds and
• SST during
• TIWs season

MODEL Wind Stress
OBSERVED Wind Stress
Chelton et al., 2001
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2.2 Atmospheric BL Adjustment to SSTsb.
Temporal/Spatial Associations
Tropical Instability Waves (TIWs) and Winds
MODEL 1999 - 2003 along 2N
SST
Stress
Div
June 2003
Jun - Dec. 1999
SST
June 2002
June 2001
Wind Stress
June 2000
Wind-Divergence
June 1999
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2.2 Atmospheric BL Adjustment to SSTsc.
Stability of Atmospheric BL Due to SSTs
Typical TIWs and Winds
September 2 - 4, 1999
Atmospheric Temp
Warm Phase 173, Cold Phase 217
UNSTABLE
September 2 - 18, 1999
Specific Humidity
Vir. Pot. Temp.
STABLE
Ocean Temp
UNSTABLE
STABLE
U-Wind
V-Wind
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2.2 Atmospheric BL Adjustment to SSTsd.
Isotherms and Wind Vectors Dynamic Feedback
Typical Patterns of Winds and SST
Chelton, 2001
MODEL
OBSERVATION
Wind Stress Divergence
Wind Stress Divergence
Wind Stress Curl
Wind Stress Curl
Chelton, 2005
Implication of DYNAMIC FEEDBACK
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2.2 Atmospheric BL Adjustment to SSTse.
Thermodynamic Feedback
MODEL SIMULATION
Less Cooling
Latent Heat Flux
Latent and Sensible Heat Flux damp the SST
anomaly Turbulent flux provides NEGATIVE
FEEDBACK To SST by TIWs.
More Cooling
Sensible Heat Flux
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3. Summary

• High-resolution ocean-atmosphere coupled model
  has been developed to study air-sea interactions
  in various parts of the World Ocean.
• Mesoscale SST induces atmospheric boundary layer
  adjustment, which may feed back onto ocean.
• Central American gap winds force upper ocean
  thermocline topography, which in turn affects
  atmospheric deep convection and precipitation.

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Thanks!
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Model Domain
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Additional Example of relations between wind
stress vector and isotherms in southern
California coastal ocean
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Model Bias Low-level CloudinessEastern Pacific

• Stratus/Stratocumulus are overestimated over
  south east Pacific (because of colder SSTs in
  model?)

1999-2000 Mean Low-level Cloud
OBSERVATION
MODEL
1999-2003 Mean SST
OBSERVATION
MODEL
Month
Month
Month
Longitude
Longitude
Longitude
Longitude