Multispectral remote sensing of aerosols

Aerosols are common atmospheric constituents that occur both naturally (clouds, sea spray, dust, smoke, and volcanic emissions) and artificially (smog, smoke, certain hazes, detonation products, and industrial emissions). Some, like the great dust bowl storms in the U.S. in the 1930s, are a combination of natural and manmade agents. Most aerosols are difficult to model because they are composed of small, non-spherical particles whose optical constants and particle sizes are poorly known. Spectroscopic observations of aerosols in the thermal infrared atmospheric window between 8 and 13.5 μm offer the opportunity to detect aerosols both day and night down to very low column densities. Such observations can also identify the gross chemical composition of the particles and, in some cases, the actual sizes and shapes. In this paper, we discuss thermal i.r. observations of three types of aerosols: satellite measurements of volcanic dust, ground-based observations of airborne desert soil and both ground- and space-based measurements of cirrus clouds.