Oceans Mapping with Sentinel-3

Our third step in the framework of World health monitoring and evaluation of climate changes effects on Earth stands on oceans and seas mapping. Copernicus Sentinel-3 mission, as already described for land products, systematically delivers to the community a large dataset of marine products, namely geophysical data extremely useful for the monitoring purposes we described in the last weeks. In this post we focus our attention on algal pigment, total suspended matter and aerosol, all products generated starting from OLCI instrument acquisitions covering August 2017.

Algal Pigment

The distribution of algal pigment is the first ocean colour product generated starting from Sentinel-3 acquisitions, computed thanks to two different algorithms able to evaluate the chlorophyll concentration in the water biomasses. This geophysical entity is expressed in mg/m^3 where values next to 0 are showed in dark blue ,higher values (around 30 mg/m^3) are in red andgreen and yellow zones are in the middle.  Algal pigment distribution could be connected to phytoplankton, thus an important aspect of rich waters. Indeed algae help to provide oxygen and food for aquatic organisms.

The image above represents another ocean colour product, namely the total suspended matter, expressed in g/m^3. The TSM indicates the quantity of suspended particles in water bodies, thus could be considered a parameter to evaluate the turbidity of water and its health. Indeed open oceans return low TSM values (can be next to 0) whereas inland waters and coastlines (e.g. river deltas) can reach 100 g/m^3 (red to black in our color scale). Several regions show some granularity: this”salt and pepper” effect could depend on several factors (maybe having not enough data), nevertheless can be mitigated with some post-processing activities (e.g. resampling of data).

Aerosols

At the end this last image showed above is a representation of the aerosols over the oceans and seas expressed in spectral dependency of the aerosol optical depth (dimensionless). An aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas and several types of atmospheric aerosol have a significant effect on Earth’s climate (volcanic, desert dust). Aerosols can be found in urban ecosystems in various forms (dust, cigarette smoke, fumes in car exhaust) and can influence the atmosphere’s climate, as well as human health, being an indicator of air pollution.

All the images have been processed in the virtual processing environment offered by the Research and User Support service of Copernicus

References:

[1] https://en.wikipedia.org/wiki/Aerosol

[2] https://sentinel.esa.int/web/sentinel/user-guides/sentinel-3-olci/product-types/level-2-water

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