Comparison of lidar and transmissometer measurements through clouds

Luc R. Bissonnette, Gerard J. Kunz, Karin Weiss-Wrana, Christopher Dainty, Luc R. Bissonnette
1996 Image Propagation through the Atmosphere  
A lidar-transmissometer intercomparison was made during an international experiment held in the German Alps to characterize the vertical structure of aerosols and clouds. The transmission path was 2325-m long and inclined at 300 along the slope of a steep mountain ridge. The transmissometer consisted of a Nd:YAG and a Co2 laser located in the valley and a large-mirror receiver that captured the full beams on the mountain top. Two lidars, one at 1.06 pm and one at 1.054 pm, were operated with
more » ... ir axes approximately parallel to the transmissometer axis but separated by a horizontal distance on the order of 20-40 m. The first one was operated in retrorefiector mode and the relative transmittance was determined from the reflection off the mountain ridge above the cloud layer. The second one had a special receiver designed to make simultaneous recordings at four fields of view. The range-resolved scattering coefficient and effective cloud droplet radius are calculated from these four-field-of-view measurements by solving a simplified model (Appi. Opt. 34, 6959-6975, 1995) of the multiply scattered returns. The two simultaneous solutions for the scattering coefficient and effective droplet size make possible extrapolation at wavelenghths other than the lidar wavelength of 1.054 pm. The main measurement event analyzed in this paper lasted 1.5 hours and produced transrnittances ranging from less than 5% to more than 90%. The comparisons show good correlation between the transniissometer data and all lidar solutions including extrapolation at 10.59 pm.
doi:10.1117/12.254163 fatcat:sbo5mbuht5f2pgdj26hm5epwue