Absorption coefficient of atmospheric aerosol: a method for measurement.

Recent models predict that the effect of atmospheric aerosol particles on global temperature depends in part on b(abs,)or on n(2), where b(abs) is the aerosol absorption coefficient, and n(2) is the imaginary part of the aerosol refractive index for radiation in visible wavelengths. Satisfactory techniques for measuring b(abs) have yet to be developed. A method for measurement of b(abs) is described and discussed. The apparatus uses a piece of opal glass to integrate light scattered by particles collected on Nuclepore filters. It is quite mobile, inexpensive, and can be calibrated. Analysis of the errors inherent in the measurement shows it is accurate to well within an order of magnitude for particles of radius larger than 0.1 microm.