Cloud Mirage at Sunset Above San Francisco, California

January 08, 2013


PhotographerMila Zinkova
Summary Author: Mila Zinkova; Jim Foster

The photo above showing a marbled strip of sky just above the western horizon offshore San Francisco, California, is actually a mirage. We’re used to seeing objects like ships and distant mountains miraged but when clouds or marine layers (cloud banks) are distorted they often escape notice. The mirage mechanism is, of course, the same: variations in air temperature and density at the air/water boundary and the layer just above it. However, in this case the entire horizon was distorted as the Sun was setting. Sunny, warm weather on this November day favored the development of a superior mirage caused by relatively warm air overlying a much cooler surface air layer. On their way to the observer, the nearly horizontal rays of sunlight were bent downward during their passage through the warmer air layer. Thus, the refracted image of the distant marine layer appears stretched above its actual position. Photo taken in late November 2012.

Photo Details: Camera: Canon PowerShot SX40 HS; Focal Length: 150.5mm; Aperture: f/5.8; Exposure Time: 0.0050 s (1/200); ISO equiv: 500; Software: Adobe Photoshop CS3 Windows.