High resolution modelling in the Western Mediterrannean: from processes toward realistic simulation Zakardjian B., Doglioli A., Forget P., Fraunie P.,

High resolution modelling in the Western Mediterrannean: from processes toward realistic simulation

Zakardjian B., Doglioli A., Forget P., Fraunie P., Hu Z., Molcard A., Ourmieres Y., Petrenko A., Schaeffer A.

Laboratoire d’OcéanographiePhysique et Biogéochimique

LSEETLSEETLab. de sondages electromagnetiques de l'environnement. terrestre

Observational evidences...From SAR images...(Platonov et al., 2007)

eddies and vortex activity in the coastal zone

interactions with the basin-scale circulation (the NC)

toward better estimate of inshore/offshore exchanges

... main problematics

From HF radar experiment, the ECOLO field campaign... (Forget et al.,

From SST images...(Rubio et al., 2009)

Modelling tools...

Model

SYMPHONIE 1 to 3 km Aladin MFSTEP 1998-2007

MARS3D 400 m to 1.2 km MM5 MENOR (1.2 km) 2006 & 2008

GLAZUR64 z (130 layers) 1.25 km (1/64°) REMO OPA MED16 (1/16°) 1999-2001

Vert. Coord. system

Spatial résolution

Atmospheric forcings

Open boundary forcings

Simul. Years

s (25-40 layers)

s (30 layers)

SYMPHONIE : originally developped at LA (Toulouse, France, e.g. Auclair et al., 2003)

MARS3D : originally developped at IFREMER for operational purpose (MENOR, e.g., Lazure and Dumas, 2008)

GLAZUR64 : high resolution OPA based regional configuration (inherited from a GdL configuration, e.g. Langlais et al., 2009)

Process study on the ECOLO eddy with MARS3D...

South wind forcingsurface generated eddy following the formation of a fresh and cold cell, i.e., Rhône freshwater pilling up eastward are blocked by coastline and bathymetry

Strong Mistral (and/or Tramontane) : bottom generated eddy following the establishment of an eastward coastal jet blocked by coastline and bathymetry

surface signature only visible after wind relaxation

Surface Okubo-Weiss parameter (10-4 s-1)

-1

+1

0

-0.4

+0.4

0

Sensibility analysis (MARS3D) of eddy activity to atmospheric forcings...

Wind stress

Surface current

(dx = 10 km dt = 3 h) (dx = 2.5 km dt = 1 h) (dx = 9 km dt = 3 h)

A strong NW wond event (6-8 June)...

(dx = 10 km dt = 3 h) (dx = 2.5 km dt = 1 h) (dx = 9 km dt = 3 h)

Sensibility analysis (MARS3D) of eddy activity to atmospheric forcings...

Wind stress

Surface current

... surface signatures of eddies during the relaxation phase

... differences in tyhe resulting eddy activity due to differences in wind curl and intensity

(dx = 10 km dt = 3 h) (dx = 2.5 km dt = 1 h) (dx = 9 km dt = 3 h)

Sensibility analysis (MARS3D) of eddy activity to atmospheric forcings...

Wind stress

Surface current

Following a one week period of low wind...

... slight differences in wind curl and intensity and time resolution affect eddy activity

The LATEX eddy, from model to field experiments...

Simulated anticyclonic eddy A1 in 2001Eddy contours detected by wavelet analysis on vorticity field (e.g., Doglioli et al. 2007, Hu et al., 2009)Duration: 32 days!!

Surface current

Bottom current

Wind

- + Sea surface level

Hu et al 2009, YSOPP Award for Ocean Science at EGU 2009

Ekman tranport following NW wind (Tramontane) and pill up of surface transported water blocked down by coastline and main circulation (the NC)...

The LATEX project...

ADCP transects (16m) and Buoy trajectories during the LATEX 2008 cruise

(Hu et al. submitted to JMS)

LAgrangian Transport Experiment (PIs: A. Petrenko and F. Diaz from LOPB) is a field based project (INSU/LEFE IDAO-CYBER and PACA Region) that aims at characterizing the dynamics of the eddy and its influence on bio-geochemical processes...

Results from pre-project LATEX0 confirm the eddy's occurrence in late spring

Main LATEX operation planned in September 2010Lagrangian floatsSF6hull-mounted ADCPsEulerian mooringssatellite imagesglidersHF radars

LOPB, LOV, LOCEAN, LSEET...

MED16GLAZUR64

MED16

GLAZUR64, the impact of high resolution on the CN dynamics...

Dynamics of the North Mediterranean current strongly modified in GLAZUR64, particularily over GdL...

... with a typology thinner and closer to the coast

Time-averaged (5 days) surface velocity centered on May 29, 2000

Time series of depth-averaged (0-300 m) velocities along a SN transec near 5.5 E

Validation with hull-mounted ADCP data...

MED16

GLAZUR64

Strong mismatch with MED16, the simulated CN is out the transect...

Better matching with GLAZUR64, both for the location and intensity of the CN

May 29 to June 1 2000Project SOFIPi: C. Grenz

Another eddy generating process...

CN instabilities at the GdL entrance can generate antiC eddies...

Another eddy generating process...

... that can migrate along the north side of the CN ...

Another eddy generating process...

... that can migrate along the north side of the CN

Another eddy generating process...

... down to the LATEX area

Another eddy generating process...

A pattern also seen in SYMPHONIE, possibly a source of negative vorticity (refueling) for the LATEX eddy...

The ECCOP project...

LSEET, LOV, LOCEAN, LEGI...

HF radar measurements Glider regular transects (monthly or less) across the CNCruises (ADCP and CTD data) of opportunity from the Tethys 2Satellite (SST, Chla, altimetry) data

Example of recent glider deployment in the ECCOP area showing the NC acceleration close to the coast and related eddy activity...

(courtesy of the European Gliding Observatories -EGO)

The ECCOP - Etude de la Circulation Côtière Provençal - project (INSU/LEFE-IDAO, Pi: P. Forget) focuses on the Toulon area as a key area constraining the typologie of the CN before its entrance on the GdL, hence its downstream dynamics...

Conclusions...The three high resolution models all simulate many eddy-like patterns on the shelf, from which at least two are supported by independant observations (LATEX and ECOLO eddies)

Those have life time from some days to some weeks, hence likely important impacts on bio-geochemical processes

The three models also converge on processes generating this sub-meso to mesoscale patterns:

- wind induced circulation constrained by bathymetry and coastline

- instabilities of the NC possibly interacting with the eddies by vorticity exchange

... and on the need for « good quality » atmospheric forcings, mainly wind intensity and curl and its short-term variability

Knowledge progress about the dynamics of such patterns still needs dedicated field experiments in order to reach unambiguous validation and process interpretation...