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Circumscribed Halo
Tangent arcs and the circumscribed halo are actually different forms of the same halo. The upper and lower tangent arc merge to form a single halo, when the the solar elevation is more than 29°. The circumscribed halo is oval-shaped and tangential to the 22° halo. It is brightest where it merges with the latter. With increasing solar elevation, the circumscribed halo becomes more and more circular until at a solar elevation of 70° it can no longer be distinguished form the 22° halo. The circumscribed halo can be much more colourful than the 22° halo.
Right hand side: high sun circumscribed halo on June 26th, 2004 also showing a 22° halo and the parhelic circle.
Below: Halo display of June 13th, 2001 showing a circumscribed halo, a 22° halo, the parhelic circle and the right parhelion. Note the bright upper part of the circumscribed halo! Olympus C-2000 Zoom, processed with Adobe Photoshop Elements.