The wind and wave atlas of the Mediterranean Sea - the calibration phase

International audienceWithin the WW-Medatlas project, sponsored by the Italian, French and Greek Navies, an extensive atlas of the wind and wave conditions in the Mediterranean Sea has been completed. The atlas is based on the information derived from the archive of the European Centre for Medium-Range Weather Forecasts, UK, then calibrated on the base of the data available from the ERS1-2 and Topex satellites. The calibration is required because the wind, hence the wave, data are normally strongly underestimated in the enclosed seas. The calibration has been done deriving the model values at each satellite position, typically at 7 km intervals. The co-located values have then been assigned to the closest grid point. This has provided a substantial number of couples of data at each point, then used to derive, by best-fitting technique, the correction required. This turns out to vary amply throughout the basin, according to the local geometry and orography. The calibration coefficients, different for wind and waves, have been used to correct the original fields and the time series at the single points. Using the calibrated data, extensive statistics have been derived, both as fields and at each point, including extreme values

The predictability of the "Voyager" accident

International audienceOn 14 February 2005 a severe mistral storm caused substantial damage to the passenger cruiser "Voyager" between Balearic Islands and Sardinia. The storm had been well predicted. However, the ship was hit by one or more, apparently unexpected, large waves. Our aim was to understand if this was a freak event or it was within the expectable probability. At this aim we use our best estimate of the local wave conditions, obtained combining modelling and measured data. Starting from these we derive the probability of large waves, considering both linear and non-linear cases. Notwithstanding a correction towards the worse of the, otherwise inconsistent, available reports, on the basis of the data at disposal we conclude that, given the local conditions, the event was within the range of the potentially expectable wave heights. This turns out to be even more the case on the basis of recent results based on theoretical and experimental data

Advection schemes and grid design

We discuss the characteristics of the first order advection scheme in coastal areas. In particular we focus our attention on the relationship between the geometry of the coast, as represented in the computational grid, and the wave fields derived from a numerical model. Having considered an alternative scheme, we show how the results may depend substantially on the characteristics of the scheme. It follows that, when modelling in coastal areas, the grid distribution and the advection scheme should be chosen taking reciprocal account of their characteristics

Oscillations in an offshore blowing wind

We suggest that, in situations where the wind is blowing from land to sea, the wind experiences some sort of inertial oscillations. This is shown by using a simplified version of the equations in the atmospheric boundary layer. In order to confirm that this effect can be present in a typical climate and weather prediction model, we have used the one-column version of the ECMWF global model. The model was used in a “Lagrangian” framework, being advected at constant speed from land to sea. Inertial oscillations, in the wind at 10 metres above the surface, are produced by this simulation. This confirms the initial conjecture. Considering the mean wind speed, the time required by the surface boundary layer to adapt to the new (from land to sea) situation is of the order of a few hours

The transfer of wind waves from the shelf to the coastal zone

We analyse and discuss the main processes that affect the characteristics of wind waves while these move through the coastal zone, towards the shore. The focus is on the influence of each process on the final results and on the overall accuracy. To this aim we make full use of two large data sets collected at different locations. Model and measured data are repeatedly compared, providing evidence of the relevance of the different processes

Can a professional development workshop with follow-up alter practitioner behaviour and outcomes for neck pain patients? A randomised controlled trial

Background: Continuing professional development (CPD) is a fundamental component of physiotherapy practice. Follow-up sessions provide opportunity for the refinement of skills developed during CPD workshops. However, it is necessary to identify if such opportunity translates to improved physiotherapist performance and patient outcomes

The oceanographic tower Acqua Alta - more than a quarter of century activity

This paper summarizes the relevant research activities that have been carried out on board of the oceanographic tower curing more than, quarter of a century of its active life. There is no special event that has triggered this paper, but the conviction that the amount of researches and results, still already published in the specialized magazines, deserves a summarizing and compact presentation. In this way it is possible to appreciate the frequent interaction among the different branches of the marine researches, and to realize how a single relevant result is always the final product of a large number of previous advances. Still with a predominance of the physical aspect, the paper covers many subjects of the marine research, moving from biology and chemistry to the physics of the atmosphere and the ocean. The location of the tower is in the Adriatic Sea, 15 km off the coast of the Venice lagoon. The limited depth (16 m) excludes any consideration of the deep water processes in the oceans, but provides the rare possibility of combining fundamental research and intensive practical applications of the obtained results. Expectably, the presence of Venice, prime reason for the existence of the tower, has been a catalyst in this direction

Hindcast and forecast of the Parsifal storm

On 2 November 1995 a Mistral storm in the Gulf of Lions sank the 16 metre yacht Parsifal claiming six lives out of the nine member crew. We analyse the storm with different meteorological and wave models, verifying the results against the available buoy and satellite measurements. Then we consider the accuracy of the storm forecasts and the information available the days before the accident. The limitations related to the resolution of the meteorological models are explored by hindcasting the storm also with the winds produced by some limited area models. Finally, we discuss the present situation of wind and wave hindcast and forecast in theMediterranean Sea, and the distribution of these results to the public

Long term directional wave recording in the Northern Adriatic Sea

We report on the instrumental system used on an oceanographic tower for the directional measurement of wind waves. The associated time series is one of the longest ones in the world. After a compact description of the instrumental part, we present some long term statistics of the wave conditions in the Northern Adriatic Sea. Then we discuss the applications of the results and the possible evolution of the system