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Cooperative Institute for Meteorological Satellite Studies / University of Wisconsin-Madison
CIMSS Tropical Cyclone Team
Saharan Air Layer (SAL) - Product Description

Meteosat-8 Pseudo-Natural Color Imagery:
Background: This product is created by combining the 0.6, 0.8, 1.6, and 3.9 µm channels on the Meteosat Second Generation satellite. The 0.6, 0.8, and 1.6 µm channels are used as a proxy for the blue, green, and red regions of the visible spectrum and are combined into a single image. The 3.9 µm channel is used to supplement these visible and near-IR channels by providing continuous coverage through the nighttime hours.
Uses: The resulting merged "color" image closely mimics what an actual color photo of the Earth would look like from space. This imagery is useful for highlighting ocean, land, aerosol (e.g. Saharan dust, pollution and biomass burning emissions), and cloud features in colors that are qualitatively similar to those of a true color image. Animations of the imagery are useful for tracking features and can help identify the source of aerosols that are indicated in the imagery.

• The visible portion of the pseudo natural color image is subject to sun glint (solar reflectance off the ocean surface). This effect can make it look "dusty", when in fact, it may not be. This area of sun glint is easily identifiable as it rapidly moves across the basin in successive images;
• Low sun angles (relative to the position of the satellite) can make it easier to see suspended mineral dust and other aerosols because scattering by these particles is greater;
• Saharan mineral dust can often be seen as far west as the Windward Islands in this imagery and appears as a brown haze;
• Biomass burning emissions appear as a deep aqua blue;
• Shallow stratocumulus and cumulus clouds appear white;
• Higher (colder) clouds appear as a light blue. This is because the three visible channels being used to create the pseudo natural imagery are only proxies for the blue, green, and red portions of the visible spectrum;


Example of a pseudo natural color image.
For more SAL information, please visit the SAL Background Information page.
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