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Twin Halos, Florida

Ron Wayman imaged these arcs above the sun at Dade City. The lower "V" is an upper tangent arc more usually seen touching the top of a 22° halo. The upper arc echoing the lower one in shape is a rarity, an upper sunvex Parry arc.

All images ©Ron Wayman, shown with permission

Parry oriented columns

Have two side faces also horizontal. Rays passing through side faces inclined at 60° generate a subset of the tangent arcs - Parry arcs. There are four types of 22° Parry arc dependant on the particular facets traversed.

Singly oriented columns

The long axis is horizontal and the column can take all rotational positions around it. Rays passing between side faces angled at 60° generate the upper and lower tangent arcs.

Both arcs change shape dramatically as the sun climbs. At sunrise they coincide and then the sunvex Parry arc ascends above the tangent arc. It disappears when the sun reaches 16° with a suncave Parry arc remaining.