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Proceedings Paper

Active probing of cloud multiple scattering, optical depth, vertical thickness, and liquid water content using wide-angle imaging lidar
Author(s): Steven P. Love; Anthony B. Davis; Charles A. Rohde; Larry Tellier; Cheng Ho
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Paper Abstract

At most optical wavelengths, laser light in a cloud lidar experiment is not absorbed but merely scattered out of the beam, eventually escaping the cloud via multiple scattering. There is much information available in this light scattered far from the input beam, information ignored by traditional 'on-beam' lidar. Monitoring these off-beam returns in a fully space- and time-resolved manner is the essence of our unique instrument, Wide Angle Imaging Lidar (WAIL). In effect, WAIL produces wide-field (60-degree full-angle) 'movies' of the scattering process and records the cloud's radiative Green functions. A direct data product of WAIL is the distribution of photon path lengths resulting from multiple scattering in the cloud. Following insights from diffusion theory, we can use the measured Green functions to infer the physical thickness and optical depth of the cloud layer, and, from there, estimate the volume-averaged liquid water content. WAIL is notable in that it is applicable to optically thick clouds, a regime in which traditional lidar is reduced to ceilometry. Here we present recent WAIL data on various clouds and discuss the extension of WAIL to full diurnal monitoring by means of an ultra-narrow magneto-optic atomic line filter for daytime measurements.

Paper Details

Date Published: 5 September 2002
PDF: 10 pages
Proc. SPIE 4815, Atmospheric Radiation Measurements and Applications in Climate, (5 September 2002); doi: 10.1117/12.482312
Show Author Affiliations
Steven P. Love, Los Alamos National Lab. (United States)
Anthony B. Davis, Los Alamos National Lab. (United States)
Charles A. Rohde, Los Alamos National Lab. (United States)
Larry Tellier, Los Alamos National Lab. (United States)
Cheng Ho, Los Alamos National Lab. (United States)

Published in SPIE Proceedings Vol. 4815:
Atmospheric Radiation Measurements and Applications in Climate
Joseph A. Shaw, Editor(s)

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