Circumzenithal Arc, Supralateral Arc and Upper Tangent Arc

September 01, 2014

Circumzenithal and Supralateral and Upper Tangent Arcs ~ Rochester NY ~ 082514~1

Photographer: Carl Crumley 
Summary Authors: Carl Crumley; Jim Foster

The photo above showing several colorful arcs in a wispy sky was taken near Rochester, New York, on August 25, 2014, at approximately 8:00 a.m. The circumzenithal, supralateral and upper tangent arcs Circumzenithal and Supralateral Arcs ~ Rochester NY ~ 082514~1featured here, from top to bottom, all result from sunlight interacting with hexagonal ice crystals found in cirrus clouds.
At left is a closer view of the circumzenithal and supralateral arcs. The circumzenithal arc (CZA) is higher in the sky and curves upward while the supralateral arc curves downward. Supralateral arcs always touch the CZA but may be mistaken with a 46-degree halo. However, with the rather low Sun angle on this late summer morning (around 20 degrees), the two arcs are tangent and not slightly separated as they would be if the Sun was lower than about 15 degrees or higher than about 27 degrees.

Photo Details: Top - Camera: Canon PowerShot SX50 HS; Lens: 4.3-215.0 mm; Focal Length: 4.3mm; Aperture: f/8.0; Exposure Time: 0.0010 s (1/1000); ISO equiv: 100; Software: Adobe Photoshop CC 2014 (Windows). Inset - Same except: Focal Length: 12.034mm; Aperture: f/6.3.