Levy, RC, Pinker, RT (2007). Remote sensing of spectral aerosol properties - A classroom experience. BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY, 88(1), 25-0.
The direct and indirect radiative effects of aerosols on climate and climate change remain a source of uncertainty in climate research (Houghton et al. 2001). Aerosols [also known as particulate matter (PM)] play an important role in precipitation processes, reduced visibility, and human morbidity (Samet et al. 2000). Before the satellite era, information on aerosols came from limited surface-based observations, which are not sufficient to describe their spatial and temporal variability. With their vantage high above the Earth, satellite observations of reflected and emitted radiances are increasingly being used to monitor aerosols and their interactions within the climate system (King et al. 1999). A highly successful project is the National Aeronautics and Space Administration's (NASA's) Moderate Resolution Imaging Spectrometer (MODIS; Salomonson et al. 1989), which has been observing from aboard the Terra (since 2000) and Aqua (since 2002) satellite platforms. By observing spectral radiances in 36 channels (from 0.412 to 14.2 mu m, see information online at http://modis.gsfc.nasa.gov) and at resolutions ranging from 250 m to 1 km, MODIS is highly suitable for deriving aerosol properties over the oceans (Tanre et al. 1996, 1997). The MODIS polar geosynchronous orbit is such that most of the globe is covered each day and completely covered every two days, thus providing comprehensive observations. Because the MODIS data are well characterized and easy to access, they are suitable for introducing students to the physics of remote sensing of aerosols. As part of a graduate course in remote sensing, students used MODIS data and focused on the following: understanding how aerosols interact with reflected solar radiation, obtaining a working knowledge of inversion techniques for retrieving aerosol properties over oceans, implementing the MODIS algorithm to retrieve aerosol properties from observations, contrasting aerosol properties from different sites and relating them to geography and season, and evaluating satellite retrievals in the context of ground-based aerosol measurements. This paper reviews the basic physics of the remote sensing of aerosols and describes selected findings and lessons learned by the students. Data, codes, and detailed instructions needed to perform the exercises are available online at www.atmos.umd.edu/-levy/ MODIS-Aerosol-Project.