Abstract
When obliquely observed from an airplane, gray clouds near the horizon are sometimes observed to overlap with white clouds. Photographic observation from an airplane and simulations using a three-dimensional radiative transfer model are conducted to understand why such clouds appear gray. From observations, the brightness depression rate of gray clouds relative to surrounding whitish clouds is about 25%, whereas in simulations, it is as high as about 30%. Conditions necessary for the observation of gray clouds are as follows: (1) two clouds at different altitudes do not overlap, but the higher cloud overlaps with the lower cloud along the line of sight when these clouds are observed in near-horizontal direction, and (2) the higher cloud is optically thin in the vertical direction, but optically thick along the line of sight.
© 2016 Optical Society of America
Full Article | PDF ArticleMore Like This
Henry H. Blau
Appl. Opt. 7(10) 1903-1905 (1968)
Gilbert N. Plass and George W. Kattawar
Appl. Opt. 7(4) 699-704 (1968)
Stanley David Gedzelman
Appl. Opt. 54(4) B165-B169 (2015)