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

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.

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

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 >10km – 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

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

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 °, ° ) 6 hourly – Global NCOM (1/8 ° ) – Initialise 6 days before

Northern Adriatic Bora Surface fluxes and stress from observations and coamps: from Pullen et al (JGR 2007) Data: Extensive previous studies include Adriatic Circulation Experiment ( ). 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.). Topography and Bora schematic

Bora Event Validation-wind stress SiteUncoupled (New) Uncoupled Pullen et al 2007 Coupled Pullen et al 2007 Venice Azalea Ancona Veli Rat Wind Stress Correlation coefficient based on 30 days of hourly data from station and from model VENICE ANCONA AZALEA VELI RAT

Bora Event Validation-net heat flux SiteUncoupled (New) Uncoupled Pullen et al 2007 Coupled Pullen et al 2007 Venice Azalea Ancona Veli Rat Heat Flux Correlation coefficient based on 30 days of hourly data from station and from model Net heat flux=long wave net (up)-incoming short wave+(sensible heat +latent heat out of ocean)

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)

Ligurian Sea Validation Site10m wind speed Solar radiative flux Long wave net flux ODAS METEO0.46 Wind speed and radiative fluxes Correlation coefficient based on 30 days of hourly data from station and from model

LASIE07: Synoptic event 25/26 June Wind speeds and vectors at 10m, 26 th June, 1700UTC. Left: COAMPS simulation, Bottom: QuikSCAT.

Ocean response (surface temperature) COOLING

SUMMARY – High resolution stand alone model runs performed for Adriatic and Ligurian Sea – Fluxes from atmosphere-only run correlate with observations typically > 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