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TitleCharacterization of the Scattering Properties of Tropospheric Aerosols as a Function of Altitude Using Multi-Angle Remote Sensing Data
AuthorGauthier, R P
SourceProceedings of the Europto '94 Conference on Satellte Remote Sensing, Rome, Italy, September 26-30; 1994 p. 129-140
Alt SeriesEarth Sciences Sector, Contribution Series 20041285
AbstractThe correction of optical remote sensing data for the effects of the intervening atmosphere has been performed for the most part with algorithms that deal with nadir sensor views over fairly wide spectral bandpasses. The advent of pointable sensors capable of off-nadir viewing and imaging spectrometers capable of offering small spectral bandpasses requires more detailed approaches in dealing with gas absorption and the aerosol scattering phase function than is currently the case with standard atmospheric correction algorithms. High resolution spectra (10nm) were obtained with an airborne platform of the atmospheric path radiance and transmittance over a large low reflectance target (a lake) as a function of view angle, view azimuth and altitude on several different days (and atmospheric states). The observations were made over a viewing range of -60 to +60 degrees at nine angles both in and perpendicular to the solar principal plane. This resulted in 18 different scatter angles at which the volume scattering of the atmosphere (corrected for the bidirectional reflectance of the background water target) could be compared with the angular behaviour of standard aerosol phase functions. The atmospheric states on the three observation days ranged from very clear to very hazy all within a period of a month during the summer (July/August) at a location situated about 250km north of Ottawa well away from any urban influences. The lake chosen was of about 16km diameter and somewhat circular thus significantly reducing any effect from the surrounding vegetation. In this preliminary study, a comparison of the angular behaviour of the surface corrected volume scattering with standard phase functions used in radiative transfer models is made. It is shown that the volume scattering behaviour for low and high aerosol optical depths follows the behaviour of standard phase functions over the whole range of scatter angles, but for intermediate values of aerosol optical depth, the observed behaviour follows different phase function behaviour depending on the scatter angle at which the atmosphere is viewed.

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