Abstract

We have measured the transmittance of cirrus clouds at 10.59-μm wavelength with a CO₂ lidar using two independent methods. The first method used backscatter from the calibration target El Chichon stratospheric cloud that was present over Boulder during 1982 and 1983. The second method used conical lidar scans at different zenith angles when uniform cirrus decks were present during the 1986 FIRE intensive observations in Oshkosh, WI. Extinction coefficients from both methods average 0.1 km⁻¹ for thin cirrus, 0.5 km thick to 0.6 km⁻¹ for cirrus several kilometers thick. There is a wide standard deviation in extinction values. Extinction to backscatter ratios vary from ~800 sr for thin clouds to 2600 sr for thick clouds.

© 1987 Optical Society of America