Accession Number:

AD1003710

Title:

Comparison of Lidar and Transmissometer Measurements Through Clouds

Descriptive Note:

Journal Article

Corporate Author:

DREV-Defence Research Establishment Valcartier Quebec Canada

Personal Author(s):

Report Date:

1996-08-09

Pagination or Media Count:

18.0

Abstract:

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 30 degrees along the slope of a steep mountain ridge. The transmissometer consisted of a NdYAG and aC02 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 microns and one at 1.054 microns, were operated with their 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 Appl. 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 wavelengths other than the lidar wavelength of 1.054 microns. The main measurement event analyzed in this paper lasted 1.5 hours and produced transmittances ranging from less than 5 to more than 90. The comparisons show good correlation between the transmissometer data and all lidar solutions including extrapolation at 10.59 microns.

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Distribution Statement:

APPROVED FOR PUBLIC RELEASE


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