Regional Air-Sea Interactions in Eastern Pacific

Regional Air-Sea Interactions in Eastern Pacific

6th International RSM Workshop

Palisades, New York

July 11-15, 2005

6th International RSM Workshop

Palisades, New York

July 11-15, 2005

Hyodae Seo

Scripps Institution of Oceanography

Hyodae Seo

Scripps Institution of Oceanography

OutlineOutline

• 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

• 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

Regional Ocean-Atmosphere Coupled ModelRegional Ocean-Atmosphere Coupled Model

1. Model and Coupler Description1. Model and Coupler Description

IC and Lateral BC: NCEP/DOE Reanalysis

SST

Boundary Layer Variables

Ocean Atmosphere

COARE Bulk Formula

Plus Winds relative to ocean

currents

Regional Spectral Model (RSM)

Lateral BC: Ocean Data Assimilation Product (JPL)

Regional Ocean Modeling System

(ROMS) • Sequential Coupling

• Coupling Frequency 3 hourly coupling Daily coupling

• Bulk Formula in BL Regional Ocean-Atmosphere Coupled Model

• Winds Relative to Ocean

Gap-Induced Low-level Winds and Air-Sea Interaction

in Central America

Gap-Induced Low-level Winds and Air-Sea Interaction

in Central America

Tehuantepec

Papagayo

Panama

OBSERVATION: Xie et al., 2005Jan-Mar SST and Windstress Climatology

2.1. Gap Winds and Air-Sea Interaction2.1. Gap Winds and Air-Sea Interaction1999-2003 Model Climatology

Ekman Pumping Velocity (10^-6 m/s)

Sea Surface Temperature (C)

Dry Hole

Costa Rica Dome

Cold SST

Winter Winter

Summer Summer SummerUpwelling by Papagayo Jet

Tehuantepec

Papagayo

Panama

Precipitation (mm/day)

Winter

Atmospheric Boundary Layer Response to Tropical Instability Waves (TIWs)

in Eastern Tropical Pacific

Atmospheric Boundary Layer Response to Tropical Instability Waves (TIWs)

in Eastern Tropical Pacific

Tropical Instability Waves (TIWs)

Global SST Image from microwave satellites Aug 25-27, 1999 (Wentz et al.)

2.2 Atmospheric BL Adjustment to SSTsa. Winds and SST 2.2 Atmospheric BL Adjustment to SSTsa. Winds and SST OBSERVED SSTs

Chelton et al., 2001

MODEL SST

MODEL Wind Stress

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

June 21 – October 20 1999

OBSERVED Wind Stress

2.2 Atmospheric BL Adjustment to SSTsb. Temporal/Spatial Associations2.2 Atmospheric BL Adjustment to SSTsb. Temporal/Spatial Associations

Wind Stress

Wind-Divergence

MODEL: 1999 - 2003 along 2N

SST Stress Div

June 2003

June 2002

June 2001

June 2000

June 1999

Jun - Dec. 1999

Tropical Instability Waves (TIWs) and Winds

SST

2.2 Atmospheric BL Adjustment to SSTsc. Stability of Atmospheric BL Due to SSTs2.2 Atmospheric BL Adjustment to SSTsc. Stability of Atmospheric BL Due to SSTs

September 2 - 4, 1999

V-WindU-Wind

Specific HumidityVir. Pot. Temp.

September 2 - 18, 1999

Atmospheric Temp

Ocean Temp

Warm Phase: 173, Cold Phase: 217

Typical TIWs and Winds

STABLE

UNSTABLE

STABLE

UNSTABLE

2.2 Atmospheric BL Adjustment to SSTsd. Isotherms and Wind Vectors: Dynamic Feedback2.2 Atmospheric BL Adjustment to SSTsd. Isotherms and Wind Vectors: Dynamic Feedback

Chelton, 2005

Chelton, 2001

Wind Stress Divergence

Wind Stress Curl

Wind Stress Divergence

Wind Stress Curl

Typical Patterns of Winds and SST

Implication of DYNAMIC FEEDBACK

OBSERVATION

MODEL

2.2 Atmospheric BL Adjustment to SSTse. Thermodynamic Feedback2.2 Atmospheric BL Adjustment to SSTse. Thermodynamic Feedback

Latent Heat Flux

Sensible Heat Flux

MODEL SIMULATION

Latent and Sensible Heat Flux damp the SST anomaly;Turbulent flux providesNEGATIVE FEEDBACKTo SST by TIWs.

Less Cooling

More Cooling

3. Summary3. 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.

• 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.

Thanks!

Model DomainModel Domain

RSM ROMS Application

Name Horizontal Resolution

(km)

Grid Size (nx*ny)

Horizontal Resolution

(km)

Grid Size (nx*ny)

EEP 50 129*86 45 147*88 camer 28 129*86 25 138*82 SCalif 20 64*65 12 108*114 SCalif2 12 64*65 5 132*138

Wind Stress Curl Latent Heat FluxWind Stress Div

Wind Stress CurlSST & Wind Stress

Over Warm Eddies: ~ 100km

Southern California Coast

Additional Example of relations between wind stress vector and isotherms in southern California coastal ocean

OBSERVATION MODEL

1999-2000 Mean Low-level Cloud

Longitude Longitude

Mo

nth

Mo

nth

Model Bias: Low-level CloudinessEastern PacificModel Bias: Low-level CloudinessEastern Pacific

OBSERVATION MODEL

1999-2003 Mean SST

Mo

nth

Longitude

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

Longitude