Background and Objectives


Background

The approved Gravity and Ocean Circulation Experiment – GOCE satellite mission is a new type of Earth observation satellite that will measure the Earth gravity field. Before the launch of GOCE in early 2009 and availability of data in mid 2010 the gravimetric geoid is not known with sufficient accuracy to allow full use of the massive sea surface height information which several satellite altimetry missions have regularly provided in global analysis of the ocean circulation. With the new information that GOCE provides substantial improvements in the modelling of the ocean circulation and transport are foreseen.

The central quantity bridging the geoid and the ocean circulation is the Mean Dynamic Topography (MDT), which is the difference between the Mean Sea Surface (MSS) and the geoid (See figure to the right). The MDT provides the absolute reference surface for the ocean circulation and for satellite altimeter data e.g. from ENVISAT, and is, when assimilated, expected to improve the performance of operational ocean and seasonal forecasting models. The determination of the mean circulation will, in turn, advance the understanding of the role of the ocean mass and heat transport in climate change.

The GOCE High-level Processing Facility (HPF), as part of the European Space Agency’s GOCE Ground Segment, is responsible for the generation of the final Level 2 products, and the generation of Quick-Look and External Calibration products. The final Level 2 products consist of the gravity field in terms of spherical harmonic coefficients and maps of the gravity anomalies and of the geoid. Mean sea surfaces are provided by a number of data centres and research institutions providing data and products from satellite altimetry. There are yet no standard procedures for combining satellite altimetry and GOCE to compute an optimal mean dynamic topography that can be used for operational ocean modelling and forecasting.

The aim of the EU FP-5 RTD project GOCINA (Geoid and Ocean Circulation in the North Atlantic) was to enhance the European capacity in Earth observation technologies by promoting and developing methods for the joint exploitation of the approved European Space Agency ENVISAT (Radar Altimeter) and GOCE missions for ocean circulation studies and associated climate modelling and operational data assimilation. A major task was to determine an accurate geoid, with error estimates, in the region between Greenland and the UK and, thereby, create a platform for validation of future GOCE Level 2 data and higher order scientific products. At the termination of the GOCINA project in November 2005 tools and procedures to enhance ocean analysis using Earth observation data from ENVISAT and GOCE were presented and delivered. Furthermore, to support the GOCE mission a set of specific recommendations for integrating GOCE in ocean circulation studies was provided. Subsequently, the user requirements and specifications of relevant products have been developed in the GOCE User Toolbox Specification project (GUTS) supported by European Space Agency.

The EU FP-6 Integrated Project “Marine Environment and Security for the European Area” (MERSEA) aims to develop a European system for operational monitoring and forecasting on global and regional scales of the ocean physics, biogeochemistry and ecosystems. The prediction time scales of interest extend from days to weeks. This integrated system will be the Ocean component of the future GMES system. The project will lead to a single high-resolution global ocean forecasting system shared by European partners together with a co-ordinated network of regional systems for European waters, which will provide the platform required for downstream shelf seas and coastal forecasting systems. Many conditions for the success of GOCE lie at the level of the processing of its data, which for a large part is going to be new to everyone. This implies that special and dedicated care of the data processing will be taken; to ensure that the best Earth’s gravity field model can be delivered to the users. Furthermore, different operational assimilation methods used in the different ocean forecasting centres will need different strategies to allow the assimilation of GOCE products. Sensitivity studies will therefore be needed to assess the impact of the assimilation on the ocean circulation and transports. It will help enormously if these sensitivity experiments can be carried out in collaboration and with the readily available advice of the community involved in processing the GOCE products for oceanographic use. Meanwhile in the preparations for GOCE, pre-launch studies can be carried out using the GOCINA products to develop strategies for the implementation of GOCE in operational ocean modelling and forecasting.

Geoid, MDT and MSS
Sketch showing the relationship between the geoid, the Mean Dynamic Topography (MDT - the mean value of the dynamic topography) and the Mean Sea Surface (MSS - the mean value of the sea surface height). The geoid can be derived from GOCE observations and the Mean Sea Surface can be derived from satellite radar altimetry such as ENVISAT RA.
(Click for a larger image)

Objectives

The main objective of GOCINO have been to complement existing research and development activities by advancing the readiness of operational oceanographic centres to incorporate new Earth observation data in their working methods and, hereby, fill a gap between current GMES projects in order to integrate and fully exploit the approved European Space Agency GOCE satellite mission for ocean modelling and operational data assimilation. GOCINO has and will support the advance of the capabilities in exploitation of EO data from the GOCE satellite mission in pre-operational oceanographic services of GMES through the following specific networking activities:
  • Dissemination of the scientific results from the EU FP-5 RTD project “Geoid and Ocean Circulation in the North Atlantic – GOCINA”,
  • Apply GOCINA products and recommendations to develop strategies for implementation of GOCE products in operational ocean models together with the ECMWF, TOPAZ, FOAM, MERCATOR, and MFS operational centres,
  • Facilitate interaction and communication between the GOCE data processing consortium and the oceanographic users to transfer knowledge and exchange experiences and requirements,
  • Promote the exploitation of GOCE data in the operational centres in the EU FP-6 Integrated Project MERSEA using the assimilation strategies for the ECMWF, TOPAZ, FOAM, MERCATOR, and MFS systems,
  • Disseminate and transfer the implementation strategies to the MERSEA project to follow up and coordinate the further implementation of GOCE data into the marine component of GMES,
  • Organisation of conferences and workshops, and
  • Development and maintenance of dedicated web pages for dissemination of information, knowledge, and experiences.
With GOCINO the knowledge and expertise build up through the research in the GOCINA project will be developed and fully made accessible for operational GOCE data users in the period up to the release of the first GOCE data.
Satellite Radar Altimetry
Full description of GOCINO Work (V 3.1)