Abstract

The classical Ångström exponent is an operationally robust optical parameter that contains size information on all optically active aerosols in the field of view of a sunphotometer. Assuming that the optical effects of a typical (radius) size distribution can be approximated by separate submicrometer and supermicrometer components, we show that one can exploit the spectral curvature information in the measured optical depth to permit a direct estimation of a fine-mode (submicrometer) Ångström exponent (αf) as well as the optical fraction of fine-mode particles (η). Simple expressions that enable the estimation of these parameters are presented and tested by use of simulations and measurements.

© 2001 Optical Society of America

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