Vertical profiles of aerosol volume from high-spectral-resolution infraredtransmission measurements. I. Methodology

The wavelength-dependent aerosol extinction in the 800-1250-cm(-1) region h as been derived from ATMOS (atmospheric trace molecule spectroscopy) high-s pectral-resolution IR transmission measurements. Using models of aerosol an d cloud extinction, we have performed weighted nonlinear least-squares fitt ing to determine the aerosol-volume columns and vertical profiles of strato spheric sulfate aerosol and cirrus cloud volume. Modeled extinction by use of cold-temperature aerosol optical constants for a 70-80% sulfuric-acid-wa ter solution shows good agreement with the measurements, and the derived ae rosol volumes for a 1992 occultation are consistent with data from other ex periments after the eruption of Nit. Pinatubo. The retrieved sulfuric acid aerosol-volume profiles are insensitive to the aerosol-size distribution an d somewhat sensitive to the set of optical constants used. Data from the no nspherical cirrus extinction model agree well with a 1994 mid-latitude meas urement indicating the presence of cirrus clouds at the tropopause. (C) 200 1 Optical Society of America.