OPOD - A day of halos, Greenland

Ice halos over the Greenland Ice Cap. Images by Ed Stockard (photostream) taken at Summit Station, a permanent research station at the highest point of the ice sheet. Ed's images show changing halos on 8th May '12.Images ©Ed Stockard, shown with permission.

Top: Sunwards showing familiar and none too familiar halos. The colourful outer halo is a supralateral arc from horizontal column crystals. The brightenings on it are possibly rare Parry supralateral arcs. The practiced eye might also see traces of helic arcs. These two halo are now often seen in 'artificial' ski-slope snow machine displays but are rare in raw nature.

Lower: Always look in the opposite direction when the sky puts on a show. Ed was looking directly away from the sun two hours after the topmost image. The same parhelic circle crosses the sky. Opposite the sun there is a bright anthelion. Rare Tricker and diffuse arcs curve upwards and downwards from it. Wegener arcs that have crossed the sky from the tangent arc slant down towards the anthelion. See the simulation below for identification.

A HaloSim ray tracing simulation of the anthelic region.

The parhelic circle is relatively weak opposite the sun.

The 'anthelion' is not a halo with distinct ray paths. rather, it is where several halo arcs cross. The upwards "Y" shape is a composite of 'diffuse arcs' and Tricker arcs. Both are rare. Both are produced by tortuous ray paths through horizontal column crystals.

Below the parhelic circle, the Tricker and diffuse arcs are close together, column like, and finally merge at the antisolar point below the horizon.

Below: Another hour onwards, the diffuse whiteness of the anthelic column of Tricker and diffuse arcs contrasts with manmade orange.