Open AccessOn the scattering behaviour of bullet-rosette and bullet-shaped ice crystals
Author(s) -
Bernhard Strauß
Publication year - 1996
Publication title -
annales geophysicae
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.522
H-Index - 93
eISSN - 1432-0576
pISSN - 0992-7689
DOI - 10.1007/s00585-996-0566-9
Subject(s) - asymmetry , pyramid (geometry) , scattering , particle (ecology) , optics , physics , wavelength , ray tracing (physics) , absorption (acoustics) , geometry , geology , mathematics , oceanography , quantum mechanics
The scattering behaviour of bullet-rosetteand bullet-shaped ice particles is investigated using model calculations (raytracing method) with special emphasis on the asymmetry factor g. Becausethe variability of the geometrical features of these particles is very large,some representative shapes are used in the calculations. The model is based ongeometrical optics, and particles are assumed to be oriented randomly; awavelength of 0.56 μm is considered; absorption is neglected. Thescattering behaviour of bullet rosettes is compared to that of single branchesout of the bullet rosette. It turns out that there are slight differences in theasymmetry factor values, depending on the lengths of the branches (∆g~0.02)and on the angles between the branches (∆g~0.01).Bullets show some special features in their phase functions due to the pyramid.The length of the particle influences the asymmetry factor (∆g~0.10),as does the shape of the pyramid (∆g~0.07). Theinfluence of the pyramidal shape decreases with increasing particle length.Bullets were compared to hexagonally shaped columns. This was done for twocolumns, one as long as the columnar part of the bullet (length withoutpyramid), and one for a column as long as the bullet including the pyramid.Asymmetry factor values of bullets with a pyramidal angle of 28° deviate lessthan ∆g~0.01 from the range given by the two values ofthe columns