@@ -77,7 +77,8 @@ The variety of physical and biological processes occurring in the ocean at diffe
The perfect observational system would consist in dense array of sensors present at many geographical locations, many depths and measuring almost continuously a wide range of parameters. Obviously such a system is not the reality: researchers have to rely on the combination of various platforms during a limited period of time, each platform measuring a given set of variables at different spatial and temporal resolutions, spatial coverage, accuracy and depth levels. We will refer to this as multi-platform systems, by opposition to experiments articulated only around the observations made using a research vessel. Further details can be found in \citet{TINTORE13}.
The western Mediterranean Sea is a particularly relevant region for multi-platform experiments, thanks to the wide range of processes taking place and intensively studied since the work of \cite{WUST61} on the vertical circulation: influence on climate \citep[e.g.,][]{GIORGI06,GIORGI08,ADLOFF15,GUIOT16,RAHMSTORF98} and sea-level change \citep[e.g.,][]{TSIMPLIS02,BONADUCE16,WOLFF18}, thermohaline circulation \citep[e.g.,][]{BERGAMASCO10,MILLOT87,MILLOT91,MILLOT99,SKLIRIS14,ROBINSON01}, water mass formation and convection process \citep[e.g.,][]{MEDOC70,STOMMEL72,SEND1999,MACIAS18}, mesoscale \citep[e.g.,][]{ALVAREZ96,PINOT95,PUJOL05,SANCHEZROMAN17} and submesoscale processes \citep[e.g.,][]{BOSSE15,DAMIEN17,MARGIRIER17,TESTOR03,TESTOR18}. Other recent instances of multi-platform experiments in the Mediterranean Sea were focused on the Northern Current \citep[December 2011,][]{BERTA18}, deep convection in the Northwestern Mediterranean sea \citep[July 2012--October 2013,][]{TESTOR18}, the Balearic Current system \citep[July and November 2007, April and June 2008,][]{BOUFFARD10} and coastal current off west of Ibiza island \citep[August 2013,][]{TROUPIN15}.
The western Mediterranean Sea is a particularly relevant region for multi-platform experiments, thanks to the wide range of processes taking place and intensively studied since the work of \cite{WUST61} on the vertical circulation: influence on climate \citep[e.g.,][]{GIORGI06,GIORGI08,ADLOFF15,GUIOT16,RAHMSTORF98} and sea-level change \citep[e.g.,][]{TSIMPLIS02,BONADUCE16,WOLFF18}, thermohaline circulation \citep[e.g.,][]{BERGAMASCO10,MILLOT87,MILLOT91,MILLOT99,SKLIRIS14,ROBINSON01}, water mass formation and convection process \citep[e.g.,][]{MEDOC70,STOMMEL72,SEND1999,MACIAS18}, mesoscale \citep[e.g.,][]{ALVAREZ96,PINOT95,PUJOL05,SANCHEZROMAN17} and submesoscale processes \citep[e.g.,][]{BOSSE15,DAMIEN17,MARGIRIER17,TESTOR03,TESTOR18}. Other recent instances of multi-platform experiments in the Mediterranean Sea were focused on the Northern Current \citep[December 2011,][]{BERTA18}, deep convection in the Northwestern Mediterranean sea \citep[July 2012--October 2013,][]{TESTOR18}, the Balearic Current system \citep[July and November 2007, April and June 2008,][]{BOUFFARD10} and coastal current off west of Ibiza island \citep[August 2013,][]{TROUPIN15}. Similar studies comparing almost synchronous glider and SARAL/AltiKa altimetric data on selected tracks have also been carried between the Balearic Islands and the Algerian coasts \citep{AULICINO18,COTRONEO16}.
Recently, the efforts carried out by data providers and oceanographic data centers through European initiatives such as SeaDataNet (\url{http://seadatanet.org/}) makes possible the creation and publication of aggregated datasets covering different European regional seas, including the Mediterranean Sea \citep{SIMONCELLI14}, upon which hydrographical atlas are build \citep[e.g.][]{SIMONCELLI16,IONA18a}. These atlas are particularly useful for the description of the general circulation, the large-scale oceanographic features or for the assessment of the long-term variability \citep{IONA18b}. However their limitation to temperature and salinity variables (as of July 2018) and their characteristic spatial scale prevent them to be employed for the study of submesoscale features.
