Microscope video of tractor soot. Video courtesy of Chere Petty, University of Maryland, Baltimore County; NSF grant DBI-0722569.
Aerosols are complex particles; they can occur in nature but can also be generated by humans. Black carbon, or soot, is generated from industrial pollution, traffic, outdoor fires, and household burning of coal and biomass fuels. Soot is a product of incomplete combustion, especially of coal, diesel fuels, biofuels and outdoor biomass burning. When soot absorbs sunlight, it heats the surrounding air and reduces the amount of sunlight reaching the ground. The heated air makes the atmosphere less stable, creating rising air (convection) which forms clouds and brings rainfall to regions that are heavily polluted. Still image courtesy of Peter Buseck, Arizona State University. Video courtesy of Chere Petty, University of Maryland, Baltimore County; NSF grant DBI-0722569.
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 220.127.116.11.0