Sea Level CCI
Climate Change Initiative (CCI) is a joint ESA and EU initiative. The CCI aims to exploit the historical archives of ESA and Third Party Mission satellites to address the requirements for a set of long term and consistent Essential Climate Variables (ECV). The variables were defined by the Global Climate Observing System (GCOS) to support the work of the UN Framework Convention on Climate Change (UNFCCC) and the International Panel on Climate Change (IPCC).
There are 44 ECVs plus soil moisture recognised as an emerging ECV. Sea Level being one of the 8 variables of the oceanic surface, is one of the 10 selected for the first round of ESA projects. Sea level is a very sensitive index of climate change and variability.
Modification of the land hydrological cycle as a result of climate variability and direct human-induced forcing leads to increased or decreased runoff, and ultimately to sea-level change. As a result, local and regional climate changes may affect sea level globally. While tide gauge sea-level data constitute one of the few long historical ocean climate time series, to monitor global sea level change and to put regionally observed changes into the global context, ocean surface topography measurements by satellite altimeters are essential. Jointly with the tide gauge network, continued operation of high-precision satellite altimetry and sun-synchronous altimeter measurements (ERS, Topex, Jason series, EnviSat…) complete the sea-level network. Together they represent an integrated strategy for monitoring of sea-level variability and change globally and on regional scale.
One high-precision altimeter is required at all times with planned extensive overlaps between successive missions, as well as two sun-synchronous, high spatial resolution altimeters to provide the needed sampling. In addition, continuous precise geoid measurements (from GOCE and GRACE space gravimetry satellites) are required to provide a reference for the altimeter data, to determine mass redistribution within the ocean, and to provide estimates of mass exchange from the cryosphere into the ocean.
ESA together with the European Union has granted the monitoring of ECV Sea Level (Sea Level_CCI ) to a consortium of nine European institutions. isardSAT among them participates as expert on instrumental corrections processing.
Even when instruments are extremely accurate, it is crucial to have them calibrated and to have instrumental corrections continuously monitored. The instrumental corrections can be from tenths of centimeters, up to a few meters. Simultaneously, requirements for the mean sea level are stringent (with precision level below the millimeter/year). Thus, it is crucial to measure and apply instrumental corrections in an extremely accurate manner. This is the aim of our task.