A study of the fine-scale dynamics in the North-Western Mediterranean Sea using altimetry, in-situ data and a high resolution regional model.

Alice Carret (LEGOS/OMP, France)


Florence Birol (LEGOS/OMP, France); Claude Estournel (LA/OMP, France)

Event: 2017 Ocean Surface Topography Science Team Meeting

Session: Advances in coastal altimetry: measurement techniques, science applications and synergy with in situ and models

Presentation type: Type Poster

One of the objectives of this study is to analyse the contribution of altimetry, in parallel with other ocean observing systems and high resolution numerical modelling, to observe and understand the ocean dynamics in the North-Western Mediterranean Sea (NWMed). This region offers a particularly interesting area in terms of coastal ocean dynamics (large range of small-scale processes) and available data (in-situ observations and numerical model outputs). It has become a pilot area for coastal altimetry studies.

In the NWMed the ocean dynamics is complex and associated with a large number of fine scale structures which are difficult to capture with altimetry. The new altimeter missions offer new perspectives for mesoscale and sub-mesoscale observation (1-100 km) but it is not always easy to separate the signal from the noise and to validate the data at short wavelength. Here, we use high-resolution numerical simulations from the Symphonie model and in-situ observations to analyse if the major regional ocean processes can or not be captured by altimetric SSH observations (because of their signature in sea level or their wavelength).

Intercomparisons between altimetry data and in situ observations and the model have first been made to study the ability of the model to reproduce the regional dynamics at different scales. In a first time we focused on the Northern Current which flows cyclonally along the Italian, French and Spanish coasts but also analysed the relative importance of the geostrophic and non geostrophic components in the surface circulation at regional scale.

The insitu data - model comparison shows a very good agreement in the variability of both the location and amplitude of the Northern Current, except in some particular cases. The comparison between insitu data, the model and Jason 2 observations shows larger differences which are still under analysis but are partly due to the resolution of altimetry data and to noise/errors in altimetry data. We have started to perform the same kind of analysis with the new generation of altimetry data (SARAL/AltiKa, Sentinel-3) in order to compare the relative performances of the different technologies. Note that this study also helps to identify altimetry errors due to uncorrect processing which might be corrected/reduced in the future.

Poster show times:

RoomStart DateEnd Date
Concerto Ballroom Thu, Oct 26 2017,14:00 Thu, Oct 26 2017,18:00
Alice Carret