Sea Surface Temperature
SST is not only one of the most famous but also one of the most important climate variables, with a solid background of measurements and analysis. By having such historical records available, SST is a vital climate change variable for marine science. It is used in NRT (less than 3 hours after measurement by satellite) for modelling forcing, front detection and SST surface patterns that report the hydrodynamic structure of the ocean upper level.
Climate prediction research and climatology is motivated by the continuous enhancement of reliable climate prediction uncertainty. This is supported by strategic advancement through input and advice to climate change assessments. SST is needed in the framework of climate model initialisation, diagnostics and fundamental climate monitoring. The most important requirement is that the observations are accurate and unbiased. Considering the best estimates of global warming trends, SST data sets should be exceptionally stable to better than 0.1 K/decade if with a mean zero bias.
Nowadays, thanks to satellite measurements, scientific teams have access to a unique and extensive source of global coverage SST observations. A very highly valued contribution to climate research is the GHRSST-PP, as a result of the GHRSST-PP Re-analysis programme (RAN). RAN is working to create an SST Climate Data Record (CDR) encompassing all satellite records (from approximately 1984). SST acuisition by the SLSTR plays an import in building this CDE long time series.
Since SST patterns change relatively slowly, they can be well predicated: in some areas of the world, up to 6 months ahead or longer. The relationships between regional SST patterns and the atmosphere can either be shown thanks to numerical models of the atmosphere and ocean or statistically connected to SST observations or data-driven analysis. A lot of seasonal prediction systems are based on dynamically coupled climate models. SST patterns and seasonal weather trends are strongly related, especially in the tropical regions. Strong signals are connected to the El Nino phenomenon in the tropical Pacific, about every three or four years, which can distort the global patterns of normal weather, modifying, by instance, seasonal rainfall patterns (floods in some area and droughts in others). In other areas of the world, weaker connections between SST and seasonal weather are established.
Daily maps of SST show thermal front location and intensity, often utilised for several applications. For instance, SST maps, combined with other information (sea surface height maps, phytoplankton) are utilised to aid catching of some fish species at different levels of the trophic chain. Thanks to surface thermal front, navies and researchers can improve their understanding and qualification of the vertical structure of the water mass and the internal wave propagation. As cold water upwelling from the sea bottom bringing up nutrients to upper layers, large ecosystems are also very well detected by SST signatures. This supervision is essential for a better assessment of variability of such ecosystems and possible fish stocks and levels of recruitment. Recently, statistical hurricane models also widely incorporate SST analyses for anticipating tropical cyclone intensity.
SST is one of the most important products regularly delivered to the GMES Service Element (Marcoast) user community and for European research projects within the remit of Corpenicus.
Figure 1: AATSR SST images: in this night-time image, the coldest areas - which include all the land - are shown in purple and blue, whilst yellow and orange are used to represent successively warmer temperatures over a total range of 280-295 K. The three blue-purple islands in the top half of the image are the Balearics and the land at the bottom of the picture is the north coast of Algeria. Eddy structures ranging in size from less than 10km to nearly 100km decorate the entire sea area. Note that the warmest water appears to originate from the Gulf de Béjaia on the Algerian coast. (Credit: RAL)
For further information about marine applications and services available, see: Copernicus website.