Ocean observations taken from space provide long-term, high-resolution global coverage of major sea surface parameters, a key input for forecasting systems. Satellite data are essential for constraining ocean models and are used for assimilation, forcing and validation.

from: MERSEA Ocean Remote Sensing Portal

Satellite altimetry measures sea surface heights; it allows the topography of the ocean surface to be charted, and helps us to monitor and understand many ocean phenomena better - for example, high- and low-amplitude phenomena, seasonal ocean variations, surface currents and ocean tides. Satellite altimetry measures the time taken by a radar pulse to travel from the satellite antenna to the surface and then back to the satellite receiver. Combined with precise satellite location data, altimetry measurements yield sea-surface heights.

Topex/Poseidon-ERS and Jason-Envisat are good examples of how altimetry satellites can operate together. Topex/Poseidon and Jason-1 follow a repeat cycle of ten days designed to monitor ocean variations, and therefore pass over the same points fairly frequently, but their ground tracks are 315 kilometers apart at the equator - more than the average span of an ocean eddy. On the other hand, ERS-2 and Envisat only revisit the same point on the globe every 35 days but the maximum distance between two tracks at the equator is only 80 kilometers.

AVISO

Satellite Sea Surface Temperature products have been developed and are disseminated by the GOS (Gruppo di Oceanografia da Satellite) in the framework of different international projects . The main operational framework for GOS SST data production is currently represented by the MyOcean (www.myocean.eu.org) project (Development and pre-operational validation of GMES Marine Core Services (2009-2012)-EU FP7-SPACE-2007-1)

The SST products are classified on the basis of their content (L3/L4), geographical coverage (MED/BLK/ITA), resolution (HR/UHR), operational chain (NRT/DT/RA) following the specifications on file naming and data format recommended by the GHRSST (www.ghrsst.org).

All GOS products are based on the measurements obtained by available satellite infrared sensors (AATSR, AVHRR, MODIS, SEVIRI). A basic description of the data produced by GOS and of their content is presented in the following:

Type of product:

• L3 data are build as a daily combination of different sensor images (only night-time data), at the required resolution, with

flag values assigned to the cloud-contaminated pixels.

• L4 data consist of daily interpolated maps obtained applying statistical space-time interpolation techniques to all available

night-time measurements. L4 data represent the foundation SST (i.e. the temperature at the base of the daily thermocline) at mid-night. A single-sensor version L4 (v0) is obtained from the AVHRR (Advanced Very High Resolution Radiometer) night-time data acquired by GOS.

Data production

• NRT (Near-Real-Time) data (both L3 and L4) are produced daily and are available within 12 hours from their nominal time.
• DT (Delayed Time) data (only L4) are produced with a 10-days delay. They provide the best estimate possible, including all data

available and using a symmetrical time window for the statistical interpolation.

• RA (Re-Analysis) data are produced offline every 6/12 months. They are build from the most recent AVHRR Pathfinder SST time

series (http://www.nodc.noaa.gov/sog/pathfinder4km/userguide.html). These re-analyses are produced in collaboration with the ENEA Special Project on Global Climate (Clim-Mod).

Resolution

• HR (High Resolution) data have a 1/16° spatial resolution.
• UHR(Ultra High Resolution) data have a 1/100° spatial resolution

Coverage

• MED Mediterranean Sea area and eastern Atlantic Ocean
• BLK Black Sea
• ITAItalian Seas

Data format The L4 data format has been defined following the conventions specified by the GHRSST-PP (Global High Resolution SST Pilot Project). L4 netCDF file attributes and variables follow the Climate Forecast (CF) convention. A full product specification can be found in the GHRSST-PP Data-processing Specification (GDS) document.

More info/data access at

GOS website <http://gos.ifa.rm.cnr.it/index.php?id=407>

Satellite Ocean Colour (OC) products (chlorophyll concentration (CHL), light diffusion attenuation coefficient (K490), remote sensing reflectance (RRS), aerosol optical thickness at all wavelenghts (TAU), L2 flags), have been developed and are disseminated by the GOS (Gruppo di Oceanografia da Satellite) in the framework of different international projects. The main operational framework for GOS OC data production is currently represented by the MyOcean (www.myocean.eu.org) project (Development and pre-operational validation of GMES Marine Core Services (2009-2012)-EU FP7-SPACE-2007-1).

Following MyOcean project versions (V0, V1, V2) the OC products are classified on the basis of their content (L3/L4), used OC algorithm (GLOBAL/REGIONAL) geographical coverage (MED/MED+BLK/ADR), resolution (HR/LR), operational chain (NRT/DT/RA) following the specifications on file naming and data format within MyOcean.

All GOS products are based on the measurements obtained by available satellite radiometer sensors (SeaWiFS, MODIS, MERIS). For the CHL product, the Mediterranean-specific algorithms are used operationally (for more details on this topic, see Volpe et al., 2007 and Santoleri et al., 2008). A basic description of the data produced by GOS and of their content is presented in the following:

Type of product:

L3- data are build the combination of different satellite swaths on a daily basis, at the required resolution (generally 1 km), a with flag value assigned to missing data. L4- data consist of daily merged images from different sensors (SeaWiFS, if still available, MODIS and MERIS). A specific product taking into account the difference between Case 1 and Case 2 water types is planned to be disseminated within V2.

Data production:

NRT (Near-Real-Time) data (both L3 and L4) are produced daily using climatological ancillary data and are available within 24 hours from their nominal time. DT (Delayed Time) data (both L3 and L4) are produced daily with a 4-day delay from their nominal time using updated ancillary data. RA (Re-Analysis) data are produced offline every time new software version or calibration coeffiencient are available.

Resolution

HR (High Resolution) data have a nominal spatial resolution at nadir of 1km. LR (Low Resolution) data have a 1/16° spatial resolution.

Coverage

MED: Mediterranean Sea area. MED+BLK: Mediterranean and Black seas. ADR: Adriatic Sea.

Data format

All data are available in both HDF (Hierarchical Data Format) and NetCDF (Network Common Data Form) formats.

More info/data access at

GOS website < http://gos.ifa.rm.cnr.it/index.php?id=373>

Daily wind fields are collected from the SeaWinds scatterometer on board the QuikSCAT satellite.

The spatial resolution of this product is 0.5° in longitude and latitude. It covers the period from July 1999 to the present. Calculation of the regular wind fields from instantaneous scatterometer observations uses an objective method based on the kriging technique with the associated variograms that consider both space and time wind vector structures. The accuracy of the resulting gridded wind fields is determined by comparisons with averaged wind parameters estimated from moored-buoy measurements in the Mediterranean Sea. The root-mean-square (rms) difference values are less than 1.5m/s. The data, documentation and facilities are available on the IFREMER Web site. The daily fields are produced every four days with one week's delay.

The Volunteer Observing Ship Program organizes the automatic collection and near real time distribution of XBT data sets covering the Mediterranean Sea and CTD data sets in coastal areas ( on line XBT data extraction )

The VOS program in the Mediterranean Sea was initially created within the framework of the Mediterranean Forecasting System - Pilot Project EC project. It continues under other national and European projects.

ADRICOSM: a research project for sustainable development supported by the Italian Ministry of the Environment Mediterranean Forecasting System - Toward Environmental Prediction: supported by the European Commission - DG Research

Many scientific institutions and SME from Mediterranean countries are contributing to the goals of MFS-VOS:

1. maintenance of XBT lines
2. development of new tools for real time data acquisition and transmission
3. implementation of monitoring strategies

Overview

During the first phase of the Mediterranean Forecasting System (MFS) a prototype system for real time physical and biochemical measurements at fixed locations was designed and developed. This prototype system, the so-called Mediterranean Moored Multi-sensor Array (M3A) was in pre-operational use during 2000 providing multiparametric data from the Cretan Sea (Eastern Mediterranean). The development of the prototype M3A was based on the experience of the TAO array of the Equatorial Pacific and the Bermuda Testbed Mooring, combining the operational capabilities of the Atlas moorings with the multiparametric configuration of the BTM system. More details about this configuration can be found at the M3A site.

The M3A system of the Cretan Sea (E1-M3A) The prototype M3A (E1-M3A) continues its operations in the Cretan Sea (south Aegean Sea, 35.66 N, 24.98 E), an extremely oligotrophic area where dense waters with intermediate and deep characteristics are formed. E1-M3A is the prototype M3A system that was developed during the first phase of the Mediterranean Forecasting System (MFSPP project). The system was in in pre-operational use between January 2000 and April 2001 providing multiparametric data from the Cretan Sea (south Aegean). The main characteristics of the E1-M3A system are the following:

• Mooring in deep sea (~ 1050m )
• Measuring capability of a) physical parameters down to 500m b) biochemical parameters down to 100m and c) air-sea interaction parameters at surface
• Raw data transmission to the operational centre of HCMR in “real time” and pre-processed data transmission to MFS partners in NRT.

The system has already provided valuable multiparametric data sets that have been used for calibration and validation of the hydrodynamic and ecosystem models developed for the Cretan Sea shelf area. The new deployment (July 2004) will provide data for the modelling efforts of the MFSTEP and MERSEA projects.

The M3A system in the Adriatic Sea (E2-M3A) This is deployed in the southern Adriatic Sea (41 2 N, 17 5 E), at a depth of about 1200 metres, another well-known area of dense water formation through open-sea convection. The centre of the Southern Adriatic is an area where vertical mass transfer (upwelling, winter convection) has a rather prominent role in distributing physical and chemical water properties and controlling the primary production (transfer of nutrients in the euphotic zone). Upwelling is determined by the intensity of the cyclonic circulation that in turn depends on the climatic conditions over the area site is therefore appropriate for moored measurements since it is possible, under certain circumstances, to neglect contributions of lateral advection processes. Within the MFSTEP project, the mooring was upgraded with oceanographic measurements within the first 200m of the water column and deployed for the TOP period in September 2004 at the E2-M3A site latitude 41°16.59’ N and longitude 17° 39.89’E.

The M3A in the Ligurian Sea (W1-M3A) This is deployed in the Ligurian Sea of the Western basin, one of the most dynamically active and productive areas within the whole Mediterranean (43 49 N 9 07 E). A permanent cyclonic circulation with seasonal and interannual variability triggered by the Tyrrhenian current dominates the area. During the winter, processes of dense water formation often occur. This is an area that has been monitored for several years in terms of surface atmospheric parameters. It is now convenient to add the remaining sensors and make the system compatible with the M3A general design.

As part of MFSTEP, NRT acquisition and processing of T/S profiles provided by autonomous profilers deployed throughout the Mediterranean have been implemented and tested.

Along with the XBT data, the NRT data provided by the profilers are the backbone of the data assimilation and forecast system at basin scale developed in the previous project.

The profilers are programmed to perform the following repetitive cycle:

- descend to a prescribed neutral depth (350 m)

- drift at that level for some time (3-7 days)

- and then dive down to about 700 m

- before ascending to the surface while collecting T/S data.

During their short period at surface, the profilers are located by, and the data are telemetered to, the satellite Argos system. Data processing, quality control and archiving is done at dedicated Data Centres. NRT distribution is done through the Internet and the data are distributed on the World Weather Watch Global Telecommunication System (GTS).

Float trajectory plots are produced in near-real time at the MEDARGO/TEDC (OGS, Trieste) and can be viewed at the following URL: http://poseidon.ogs.trieste.it/sire/medargo/active/index.html

MEDARGO full datasets can be visualized and downloaded in quasi-real time through the MFSTEP Data management web site.

Although differing in details due to the characteristics of the Mediterranean Sea, MEDARGO is similar to the international ARGO program started in 2000. ARGO consists of a global array of T/S profiling floats for the desciption of the evolving state of the upper world oceans and the patterns of ocean climate variability. Considerable interaction is therefore envisaged between MEDARGO and ARGO in terms of data sharing, sharing of tools for data processing and visualization and scientific evaluation and results.

Gliders are autonomous submarine vehicles designed to observe the ocean interior at a lower cost than oceanographic ships. This technology has the potential to bring tremendous benefit to an observing system for a basin with scales like the Mediterranean.

These are autonomous gliders, which can “fly” underwater on slightly inclined paths, using only their buoyancy for propagation. A typical dive/ascent to 1000 m depth moves the glider horizontally by around 4 km at a horizontal speed of about 40 cm/s. During these casts, the glider can measure temperature and salinity. When the Glider is at surface, positions obtained by GPS and the data collected at depth are transmitted to the land base via a 2-way satellite communication system. The glider steers itself autonomously, but can also be controlled remotely to change its mission programming or to command it back to the base.

For further information about gliders see the IFREMER gliders web site.

The Mediterranean Surface Velocity Programme (MedSVP) is responsible for the co-ordination of surface drifter operations at the Mediterranean level. This includes the following activities:

1. The co-ordination of drifter deployment in the Mediterranean;

1. The processing of drifter data with specific QC tailored for the Mediterranean, both in NRT and delayed mode;

1. The preparation and distribution of Mediterranean drifter products and services;

1. The comparison of Mediterranean drifter data with ancillary surface velocity data (e.g. HF radars) and model products.

MedSVP is part of the Italian “Gruppo Nazionale di Oceanografia Operativa” (GNOO) and of the Mediterranean Operational Oceanography Network (MOON).

The MedGLOSS network consists at present of NRT stations and delayed-mode stations, with a total of over 43 stations. However, at present only 15 stations are providing NRT data, whilst the delayed-mode stations are expected to provide hourly data updated twice a year. More information may be found at the MedGLOSS site

ENEA co-ordinates the ship-of-opportunity network of the Mediterranean basin.

OGS co-ordinates data collection from mooring and Lagrangian profiling buoys as well as ecological forecasting.

CNR co-ordinates the real-time satellite data analysis for forecasting, data collection from mooring buoys and oceanographic cruises, and collects physical and biological data using the Fishery Observing System (FOS)