High-resolution simulations of air-sea interaction in the Mediterranean Sea

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High-resolution simulations of air-sea
interaction in the Mediterranean Sea
AMS 16th Conference on Air-Sea Interaction, Jan.
11-15 2008.

• R. Justin Small,
• Travis Smith, Tim Campbell, Rick Allard, Jim
  Dykes
• Naval Research Laboratory, Stennis Space Center
• Joao Teixiera, Jet Propulsion Laboratory, NASA
• Acknowledging
• Sue Chen, Jim Doyle, NRL Monterey
• Julie Pullen NRL Monterey/Stevens Lab NY

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Introduction

• Advantage of a mesoscale or regional coupled
  model for forecasting
• Regional-Large scale influence constrained by
  boundary conditions
• Mesoscale-Focus on smaller scales of interest
  (high resolution)
• Coupled-Self-consistent local ocean, atmosphere
  and wave forecasts
• Coupled Improve fluxes etc. by allowing
  components to interact
• Evolution of coupled boundary layers important
  for Naval operations
• e.g. acoustic detection (Sonar) good fluxes and
  stresses needed for proper forecasting of mixed
  layer depth, thermocline gradient, waves
• e.g. surface drift surface currents consistent
  wind, waves, currents required.

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Aims

• To validate the coupled model against
  experimental data.
• Adriatic Circulation Experiment February 2003
• Ligurian Sea Air-Sea Interaction Experiment
  June/July 2007
• To investigate fine-scale wind events due to
  steep land topography and their effect on the
  ocean
• Sensitivity to resolution
• Sensitivity to coupling
• Starting with (preliminary results)
• Flux comparisons

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Numerical Model

• COAMPS (Coupled Ocean/Atmosphere Mesoscale
  Prediction System)
• Non-hydrostatic, compressible, sigma coordinate
• Explicit microphysics for 10km or less grid
  space
• Kain-Fritsch (1990, 1993) for gt10km
• Modified Louis (1979) surface layer
• NCOM (Navy Coastal Ocean Model)
• Hydrostatic, incompressible, Boussinesq
  approximations
• free-surface, mixed sigma(upper) and
  z-level(lower)
• Mellor-Yamada vertical mixing

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Coamps5 Regions -Mediterranean

• Northern Adriatic Sea
• Events of interest winter-time Bora

Ligurian Sea
Events of interest Alpine Lee cyclogenesis and
strong winds in summer
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Experimental design

• Atmospheric nests
• 3 nests, 27 km, 9km, 3km grid spacing
• 30 levels
• Ocean nests
• 2 nests, 6km, 2km
• 30 levels
• Initial and Boundary conditions
• NOGAPS (2003, 1, 2007 0.5) 6 hourly
• Global NCOM (1/8)
• Initialise 6 days before

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Northern Adriatic Bora
Surface fluxes and stress from observations and
coamps from Pullen et al (JGR 2007)
Topography and Bora schematic
Data Extensive previous studies include Adriatic
Circulation Experiment (2002-2003). Stress and
flux data for 1 month at gas platforms and land
stations (Jan/Feb 2003 Dorman et al 2006), ship
data. Previous Modeling includes a file-based
coupled coamps experiment (Julie Pullen, Jim
Doyle, Tracey Haack). Aim to reproduce and
possibly extend their results with the ESMF-based
coamps5. (e.g. utilising different coupling
options, timesteps etc.).
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Bora Event Validation-wind stress
Site Uncoupled (New) Uncoupled Pullen et al 2007 Coupled Pullen et al 2007
Venice 0.59 0.68 0.64
Azalea 0.63 0.52 0.46
Ancona 0.38 0.56 0.59
Veli Rat 0.77 0.71 0.69
Wind Stress Correlation coefficient based on 30
days of hourly data from station and from model
VENICE
AZALEA
VELI RAT
ANCONA
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Bora Event Validation-net heat flux
Site Uncoupled (New) Uncoupled Pullen et al 2007 Coupled Pullen et al 2007
Venice 0.79 0.55 0.57
Azalea 0.84 0.75 0.77
Ancona 0.61 0.69 0.7
Veli Rat 0.92 0.72 0.73
Heat Flux Correlation coefficient based on 30
days of hourly data from station and from model
Net heat fluxlong wave net (up)-incoming short
wave(sensible heat latent heat out of ocean)
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LASIE07 (PI Joao Teixiera)
Data LASIE07 (June/July 2007, PI Joao
Teixiera). Over 300 ocean profiles, 100
radiosondes, 2 surface met moorings, wave buoys,
drifters, ADCP, thermistor moorings. Aim to
better understand coupled boundary layer
processes. Example process strong summer
Mistral winds cool SST how deep does this
affect extend and is there a feedback to
atmosphere? Impact on clouds, heat fluxes and
stress. Change of wave field.
La Spezia NATO Undersea Research Center (NURC)
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Ligurian Sea Validation
Site 10m wind speed Solar radiative flux Long wave net flux

ODAS 0.57 0.96 0.8
METEO 0.46
Wind speed and radiative fluxes Correlation
coefficient based on 30 days of hourly data from
station and from model
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LASIE07 Synoptic event 25/26 June
Wind speeds and vectors at 10m, 26th June,
1700UTC. Left COAMPS simulation, Bottom
QuikSCAT.
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Ocean response (surface temperature)
COOLING
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• SUMMARY
• High resolution stand alone model runs performed
  for Adriatic and Ligurian Sea
• Fluxes from atmosphere-only run correlate with
  observations typically gt 0.5.
• WAY AHEAD
• Preliminary coupled runs being performed
• Validation of model against in-situ profiles in
  the atmosphere and ocean
• Investigation of coupled effects during strong
  wind events
• Validation in other regions against datasets
  such as KESS, CLIMODE, CBLAST