Monday, 4 February 2008
Snow surface display with 9° and 24° halos
22° halo is the dominating feature, but closer look reveal also halos from pyramid crystals. In darker version of the same image 9° halo is visible and a short patch of 24° halo is seen on the right where the 22° halo meets the forest ( 1 ).
Earlier, an odd radius halo had been observed on snow surface in Germany, where Richard Löwenherz saw 24° halo accompanying the 22° halo on 10 December 1998 ( 1 ). On 3 December 1986 in Kuopio, Finland, Juhana Hakumäki observed 9° and 22° halos on frosty window. The 22° halo was reported to have double spectrum, an indication of the presence of 24° halo.
Crystal photos from surface halo displays are scarce and as far as I know none are available from the displays with odd radius halos. However, pyramid crystals have been sampled from snow surface. At South Pole in December 1998 Jarmo Moilanen decided to have a look at the snow surface composition under a microscope, and to his surprise saw pyramid crystals ( 1 - 2 ). Unfortunately sun was too high to see the possible odd radius halos.