Aerosol Optical Depth Retrievals from High-resolution Commericial Satellite Imagery over Areas of High Surface Reflectance

Atmospheric aerosol particles impact the Earth’s energy budget through reflection and absorption of solar radiation (the aerosol direct effect) and modification of cloud properties (the aerosol indirect effect). The scattering of incoming solar radiation back to space results in a net decrease in heating at the Earth’s surface. The absorption of solar energy alters the atmospheric heating rate, which influences atmospheric circulation. The indirect effect works to increase cloud albedo at solar wavelengths by providing additional cloud condensation nuclei that often produce more and smaller drops that subsequently result in brighter clouds. Again, this reduces heating of the atmosphere and at the Earth’s surface. When compared to the global heating caused by anthropogenic greenhouse gases, cooling due to aerosols has the potential to offset greenhouse gas warming by approximately 25 to 50% (IPCC 2001, Twomey et al. 1984, Charlson et al. 1992, Kiehl and Briegleb 1993). The effects of aerosol particles, however, are much harder to characterize and quantify than those of greenhouse gases. Greenhouse gases have a relatively homogeneous distribution globally and a lifetime of up to 100 years or more (IPCC 2001, Prather 1996, Smith and Wigley 2000). Aerosol particles have heterogeneous spatial and temporal distributions with life spans on the order of days to weeks (IPCC 2001). Recent research efforts, especially in the fields of remote sensing and modeling, have focused on characterizing the climatic effects of sources and distributions of natural and anthropogenic aerosols. Much effort has been focused on aerosol characterization using satellite observations due to the extensive area covered by satellites combined