Europe Sentinel-3 Mosaic

What about one of the first Sentinel-3 cloud free mosaic covering Europe with all its land parts and seas? The following image has been generated mosaicing around 300 Level 2 products of OLCI and SLSTR instruments, representing a synergic contribution of two different processing systems, since products covering land have been generated by ESA and products covering water bodies have been processed by EUMETSAT. Indeed continental Europe is pictured with the OGVI (OLCI Global Vegetation Index), an OLCI product optimised to assess the presence on the ground of healthy, live, green vegetation: forests and woods return a greater index than other land parts and so it is possible to have a complete overview of the vegetation distribution. On the other hand the seas have been pictured with the Sea Surface Temperature (or SST) acquired by the SLSTR instrument thanks to its infrared bands, capable to detect the temperature of bodies on the Earth surface.

Vegetation and Sea Temperatures over Europe

The vegetation index has been processed using Sentinel-3 land data acquired in July 2017 over continental Europe and with a yellow-green scale classification. Greener is a region, greater is the OGVI and so the presence of forest and vegetation. Appennines, Pyrenees and the Alps surronding areas are highlighted thanks to their vegetation, just like the Ireland appears almost completely green. The most extended ecoregions are the Western European broadleaf mixed forests, the Carpathians mountains forest (spread all over the romanian country) or the green zone in the northwestern part of the Balcans. On the other hand Spain or Turkey offer a more desertic landscape because of their lack of vegetation. Indeed in Spain we can see also black areas, where the vegetation index is null: that’s the case of the Monegros desert in Aragon and of the majority of northern part of Africa. Only small parts of Morocco, Tunisia and Algeria have green zones, however they are surrounded by the Sahara desert. The Egypt case is curious, where the vegetation follows the Nile and grows along the course of the river and all around its delta. Other black zone are observed over the Alps and in Norway: in this case the missing vegetation index is due to ice.

Another particular case is the Almeria region, in the southern part of Spain: around 26000 hectares of greenhouses have been built in the last decades so the landscape is completely arid (the other surrounding black zone belong to the Tabernas desert and some other desertic lands near Guadix). At the end in the global Europe mosaic there are other black parts, just like somewhere in Wales or Finland, due to clouds: satellite data have been acquired in a time range from the beginning and the end of July 2017, when Sentinel-3 didn’t probably manage to get a free cloud acquisition of those countries.

Seas surrounding europe have been instead pictured with Sentinel-3 marine data and specifically with the sea surface temperature detected by the infrared bands of SLSTR. All the data are overnight acquisitions, selected in order to avoid the direct sun radiance contamination for the temperature detection and estimation. The data have been acquired in the second half of October and the first days of November 2017. The chosen temperature scale classification is a gradient blue where the darkest seas are the coldest (around 270 K) whereas brighter water bodies are the hottest (detected temperature around 300k). The pattern is clear, with increasing temperatures from the south to the north. Indeed the hottest seas are the Red and Dead Sea, where instead the Mediterranean Sea offers temperate climates compared to the Atlantic Ocean and Black Sea. Going North the climate became colder: the sea of Azov, The Baltic sea and of course the North sea have around 0°C of temperature. The T° gradient from south to north is more appreciable with the following different colour classification, spanning all the visible spectrum and characterizing cold-hot waters respectively with blu-red nuances.

Sea Surface Temperature over Europe

In this case the continental parts are masked in black and inner water bodies are more visible: tha’s the case of the main european rivers just like the Danube, Rhine, Loire and the Dnepr, the Vättern and Vänen lake in Sweden, the Norwegian fjords and Ladoga or Onega lake in Russia as well.

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The mosaics and images have been generated in one of the virtual machine provided by the Research User Service offered in the framework of the Copernicus Programme as well. Data have been downloaded from che Copernicus Open Hub and Copernicus Data Access

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