Superior Mirage of Farallon Islands

November 11, 2011

Fata morgana 11-02-11 183

Photographer: Mila Zinkova; Mila's Web site
Summary Author: Mila Zinkova

November 2011 Earth Science Picture of the Day Viewer's Choice

The photo above shows the unidentified flying object (UFO) I observed at Ocean Beach in San Francisco on November 2, 2011. It was not only hovering over the ocean surface but was constantly changing shapes. See photo inserts. My excitement grew when I noticed  a small boat, perhaps a U.S. Coast Guard cutter (left of UFO) that surely was sent out to investigate this incident...

So did I observe an UFO? No, not exactly. But what else other than an alien space ship of some kind could change shapes in place while hovering above the sea? Atmospheric optics sometimes works to allow us to see things differently than they actually appear. The “UFO” I saw was simply a superior mirage of the Farallon Islands. These small islands are too far to be seen from shore (they’re below the horizon – approximately 25 mi or 40 km from Ocean Beach). However, the weather on November 2 was unusually hot and eerily calm, which favors the viewing of superior mirages. On this afternoon, a layer of very warm air blanketed the much cooler sea water. This resulted in nearly horizontal rays of sunlight being bent downward as they passed upward through the much warmer air, so that the refracted image of the islands appeared above their actual position. Atmospheric inversions such as this permit us to see objects that are beneath the horizon. Although I’m able to observe mirages of the Sun almost every clear sunset from Ocean Beach, I’m only able to view superior mirages of terrestrial objects a few times a year. I never tire watching the amazing performance of the seascape changing before my eyes. By the way, anyone on the ship would not have been able to see the mirage in the same way I did. Always protect your eyes when looking toward the Sun.