Applications of an Airborne Ruby Lidar During a BOMEX Program of Cirrus Observations

A ruby lidar was mounted in an aircraft to obtain measurements of cirrus and haze layers concurrently with an airborne infrared radiometer during Project BOMEX in July 1969. The capability of the lidar for detecting cirrus or haze layers and for describing directly their range and thickness provided uniquely the information essential to a meaningful analysis of radiometric data. In addition to the geometric descriptions, analyses of lidar returns were performed to determine optical parameters. The procedure for conducting these analyses required that an average profile of the clear air backscattering coefficient in the troposphere above the boundary layer be established. Samples of lidar data and derived optical parameters are shown; one illustration includes data from a dense dust layer below an altitude of 12,000 ft. Comparison of analyses of lidar and radiometric data from cirrus clouds indicated that the infrared transmittance (10.2–11.6 μ) was directly related to the geometric thickness of the cloud. This important statistical result suggests a basis for simplified modeling of the influence of cirrus on infrared transfer.