The atmosphere is made up of gases like oxygen, nitrogen, and water vapor, but it also contains tiny particles called aerosols. Aerosols come from both natural and human sources and include things like sea salt, dust, soot, and sulfates.
Aerosols often contribute to air pollution and poor visibility. Once they are in the atmosphere, they can travel long distances, affecting air quality far from their source. Aerosols also absorb or reflect energy (light), influencing temperatures in the atmosphere and on the ground. Satellites measure aerosols by how much light can pass through them. A thick layer of aerosols will block the ground from view, while a thin layer allows enough light through to see the ground. The measurement is called aerosol optical thickness.
The GEOS-5 model is built on satellite data and provides a forecast of aerosol optical thickness (among other things). This animation shows a daily updated 10-day forecast of aerosol optical thickness from GEOS-5. The date and timestamp are in the lower left corner. In general, brighter colors are thick aerosols, while dull darker colors are thin aerosols.
Blue represents sea salt (sea salt extinction aerosol optical thickness, 550 nm). Winds blowing across the ocean kicks up ocean spray, which includes sea salt. In the animation, pale blue to white colors reflect stormy conditions. Individual large storms like tropical cyclones (hurricanes, typhoons) are visible as swirling circles of thick sea salt.
Red represents dust (dust extinction aerosol optical thickness, 550 nm). The Saharan Desert of northern Africa is the largest source of dust, but dust can be seen across the globe. Saharan dust often interacts with tropical cyclones.
Green represents the sum of aerosol optical thickness for organic carbon, black carbon, and sulfate. Organic and black carbon come from burning biomass or fossil fuels. Sources include fires, power plants, vehicles, and other combustion engines that run on fossil fuel. Sulfate particles come mostly from burning fossil fuels, but also from volcanoes.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 184.108.40.206.0