Aerosol properties derived from aircraft multiangle imaging over Monterey Bay

Abstract

The first generic and climatological aerosol retrievals using AirMISR data are presented. Multiangle observations at 672 and 867 nm, in a cloud‐free region over dark water in Monterey Bay on June 29, 1999, yield complementary generic and climatological results. The generic retrieval produces cross‐section‐weighted, column‐mean aerosol properties: midvisible aerosol optical depth between 0.05 and 0.10, with a preference for values on the low side of the range, particle number‐mean characteristic radius between 0.25 and 0.45 μm, and imaginary index of refraction <0.004, with 0.0 as the most likely value. These properties correspond to a “medium‐to‐large, spherical” column‐average particle. The climatological retrieval identifies a maritime air mass, having a total aerosol optical depth about 0.1, and mixing ratio for sea‐salt particles (large, spherical) of 50%, based on optical depth in MISR Band 2, and 40% for the sulfate plus carbonaceous (medium, spherical) components, to an accuracy of about ±15%. These results are in good agreement with the limited nearby surface‐based and aircraft observations available. The analysis also shows that over dark water, pixel‐to‐pixel scene variability can contribute more to the retrieval uncertainty than camera calibration and that high spatial variance of the reflectance, in addition to geometric considerations, is a better indicator of Sun glint contamination than geometry alone. This work represents an early step toward the goal of using MISR multiangle data to add spatial detail and information about temporal variability to the global aerosol climatology.