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

GOES Natural Color Imagery:
Background: This imagery is created by combining the 0.64 µm, 0.86 µm, 0.47 µm and 3.9 µm channels on the GOES-East satellite. The 0.64, 0.86, and 0.47 µm channels are used as a proxy for the red, green, and blue regions of the visible spectrum respectively and are combined into a single image. The 3.9 µm (shortwave window band) channel is used to supplement these visible channels by providing continuous coverage through the nighttime hours.
Uses: This merged "color" image 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 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. Because of the operational location of GOES-East (~75°W), SAL dust is more easily seen in this imagery from sunrise to late morning.
• During the summer months, Saharan mineral dust can often be seen spanning from the Caribbean to Africa in the natural color imagery and appears as a brown haze.
• Land areas have an overemphasized green shading in the natural color imagery because the GOES-East green channel (0.86 ┬Ám) is only a proxy for the green wavelength (~0.54 µm).

For more SAL information, please visit the SAL Background Information page.