Report
MFSTEP WP6 + WP4 meeting
Trieste 17-18 June 2003
CNR - ISMAR, Sezione di Trieste
viale R. Gessi 2
34123 Trieste
17 June
14:15 People meet
14:30-15:30 V. Rupolo – Simulations of MedARGO trajectories
He first described the tasks in which ENEA is involved.
Then he described in details the work to be done in subtasks 4110 4120 4130
He describe the ARGO float cycle.
The algorithm has been implemented.
The velocity field can be extracted from perpetual year or a specific year run.
A question arises whether the integration should be offline or online. Offline integration is planned,
which can manage a large number of particles. The useful information is provide by the ensemble
of many trajectories, not by individual trajectories. At the moment particles tend to crash at 700 m
depth, but this problem is solved in principle.
The Eulerian velocity field is sampled every 4 days.
Then he showed some tests using a 3-day cycle.
In the assimilation of T/S profiles it is planned to use the same lagrangian algorithm and the same
methodology used in the assimilation of the XBT profiles.
Volfango reports that A. Griffa and A. Molcard need an on-line lagrangian algorithm for position
assimilation.
15:30-16:30 G. Larnicol – ARGO float simulations
He first described the task in which his group is involved. The objective is to study the impact of
MedArgo data for the estimation of the 3-D thermohaline field.
Gilles will estimate the optimal number of floats for the Mediterranean, Volfango the optimal grid
of deployment, given the float number (e.g. 20)
Then he described the methodology and showed results from an experiment in the Atlantic Ocean.
He remarked about the ability, measured as error reduction, of the combination (via Optimal
interpolation) of the MedArgo T/S field and that estimated from Altimetry and SST to reproduce
large scale and instantaneus fields.
Issues to be discussed:
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model to be used
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eulerian simulations (weekly fields)
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lagrangian simulations
o simulation of profiling floats with an regular array

fields: T,S, absolute dynamic topography, barotropic and baroclinic components

period: at least one year

standard levels: 0 to 700 m
Discussion:
Volfango: 50 km (COSA ?)
Pierre: Floats in most of the basin is the main objective.
Volfango: concerning lagrangian simulation we can provide 0.5*0.5°, 1*1° and 3*3° float array
sizes.
Perpetual year to be asked in Bologna (eulerian to be given to Volfango and to Gilles)
Tipical year (high freq forcing and the model should be at equilibrium)
If tipical medargo profile can resolve the main features
Lagrangian not to be repeted (1 specific year: 2000)
Minimize the work with something that is already available with altimetry data assimilation
16:30-17:00 Coffee break
17:00-18:30 Discussion on the implementation of MedARGO OSSEs
18 June
09:00-09:45 F. Raicich – TS assimilation
He first summarized the MFSPP twin experiments. He gave examples of assimilation experiments
involving XBT from VOS and AXBT surveys.
He showed comparisons of different sampling strategies in terms of ratios between errors in the
assimilation run and in the free run in winter for the west basin. The analysis is performed for three
different layers.
The VOS track coverage in MFSPP was poor as shown by a small data impact in the forecast
model.
The effect of removing one track from the network shows its importance.
In the last months he moved to TS bivariate assimilation (assimilate T and S and correct both).
It makes use of TS bivariate EOFs.
He showed comparisons of bivariate assimilation of T and S, of T only and univariate T
assimilation with the basic VOS sampling strategy.
He showed corrections for salinity which are not possible in the univariate case.
Since the experiments do not involve real observations, thay are indipendent of the initial condition
and the period of simulation. At the moment the year 2000 is chosen
Gilles: What about assimilation of satellite altimetry?
Fabio: It will be used to control the runs similarly to the atmospheric forcing, not as an experiment
parameter like T and S.
Volfango: Did you find important tracks in the western basin?
Fabio: Tracks 1 and 2 are shown to be important due to their length and the extent of basin
coverage.
09:45-10:30 G. Crispi – Biomass assimilation in coupled ecosystem-hydrodynamical model
The simulation is done with a model NPZD (Description of the model).
The assimilation scheme is the Optimal Interpolation of SOFA, that will be implemented for
biogeochemical variables.
There problems for compilation on ORIGIN machine, now the problems are solved.
There are difficulties concerning parameterization in SOFA, as the correlation function for
temperature will be substitute with that for biomass.
The Ecosystem-hydrological numerical model is described. Nutrient distribution and seasonal
pattern, trophic gradients are represented.
The restart date chosen was 1 February 2000.
Then he described the Task 6400 Ocean Colour OSSEs for the Mediterranean Sea
10:30-11:00 Coffee break
11:00-12:15 Discussion on the implementation of TS and Ocean Color OSSEs.
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Choice of model configuration and forcing for MOM: monthly mean wind stress, cloudiness,
temperature, salinity.
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Implementation of surface and subsurface layers in SOFA, to introduce data in the proper way.
12:15-13:00 Overall summary of interactions, timelines, ecc...
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Web site for WP6.