Colored halos are produced by refraction of light by solid hexagonal snow crystals with well-defined facets whose size is sufficiently large (>20 μm) to avoid significant diffraction effects. Large crystals fall with their major axes horizontal and oscillate by eddy shedding to give dogs and arcs. The formation of such crystals is strongly dependent on changing growth conditions, particularly ice supersaturation, air pressure, temperature, and the thermal radiation environment. Optimum meteorological conditions for formation of such crystals are suggested.
© 1987 Optical Society of America
Original Manuscript: July 7, 1986
Manuscript Accepted: November 28, 1986
Published: March 1, 1987
John Hallett, "Faceted snow crystals," J. Opt. Soc. Am. A 4, 581-588 (1987)