The single and multiple scattering and absorption properties of hexagonal ice columns with different degrees of particle orientation are modeled in the solar spectral range by means of a ray-tracing single-scattering code and a Monte Carlo radiative-transfer code. The scattering properties are most sensitive to particle orientation for the solar zenith angles of 50° (asymmetry parameter) and 90° (single-scattering albedo). Provided that the ice columns are horizontally oriented, the usual assumption of random orientation leads to an overestimation (underestimation) of the reflected (transmitted) solar broadband radiation at high Sun elevation and to an underestimation (overestimation) at medium solar zenith angles. The orientation effect is more (less) pronounced in scattering and transmission (absorption) for smaller ice crystals.
© 2006 Optical Society of America
Original Manuscript: February 3, 2005
Revised Manuscript: June 23, 2005
Manuscript Accepted: September 8, 2005
Susann Klotzsche and Andreas Macke, "Influence of crystal tilt on solar irradiance of cirrus clouds," Appl. Opt. 45, 1034-1040 (2006)