Atmospheric
Optics
Shetland halos
Imaged by Austin Taylor (photography) on the Island of Shetland, Scotland.
©Austin Taylor, shown with permission
Enhancements and a simulation confirm the Lowitz arcs.
The slightly enhanced image (A) hints at a middle Lowitz and perhaps a lower Lowitz.
The colour subtraction (B) brings out the middle Lowitz.
But conventional levels adjustment (C) followed by violent unsharp masking perhaps reveals them best.
At far right a HaloSim ray tracing shows
the arcs' positions.
The 'weakening' of the 22° halo near the sundogs is relative. The 22° halo position at 2 and 4 o'clock is strengthened by overlap of the upper and lower Lowitz arcs.
Above the sun is an upper tangent arc and then an indistinct Parry arc. At top of the image is a a circumzenithal arc. Faint and broad at this solar altitude.
At far left and right coloured infralateral arcs shine.
There is more. Look at the faint arc outside the 22° halo and passing through the right hand sundog. Notice that the 22° halo is fainter close to the sundogs. Lowitz arcs! Always look for these clues.
A hazy 22° halo circles the sun. Sundogs (22° parhelia) flank the sun but are further than 22° away at this solar altitude. A bright parhelic circle passes through them.
