Atmospheric Mirages
Atmospheric mirages:
- the inferior mirage
- the superior mirage
True or false: Light travels in straight lines.
True or false: Light travels in straight lines.
True! But only in a homogeneous medium.
Refraction: the bending of light rays
Is the atmosphere a homogeneous medium?
Air pressure:
- decreases with increasing altitude
- lowers the density
Air temperature:
- decreases with increasing altitude
- increases the density
The pressure and temperature effects counteract each other when the
temperature lapse rate is 0.0375oC/m. At this lapse rate, light rays
travel in straight lines.
Temperature profile for the “desert mirage”
Temperature profile for a superior mirage.
Inferior mirage
Harald Edens, http://weather-photography.com
Harald Edens, http://weather-photography.com
Paul Avery, Dept. of Physics, University of Florida
Why does the mirage look like water?
“Your mind always tries to make sense out of the visual images presented to it by the eye, and this one is easy
to interpret. The only other place in nature where you see a tree [or a car] sitting above it’s inverted image is
when you view it over a water surface and see its reflection. So what you perceive is water...”
- Robert Greenler, University of Wisconsin-Milwaukee
Inferior mirages and the vanishing line
Robert Greenler,
Rainbows, Halos and Glories
The superior mirage
The appearance of the false image depends on the
strength and thickness of the temperature inversion
The superior mirage: “looming” images
These icebergs are below the horizon
Paul Avery, Dept. of Physics, University of Florida
The island appears to float
above the horizon.
Daniel Harnos, Princeton University
The superior mirage: “towering” images
Sechrist, R.S., R.W. Fett, D.C. Perryman. 1989, Forecasters Handbook for the Arctic.
Naval Environmental Prediction Research Facility, Monterey, CA 93943-5006.
Technical Report TR 89-12.
The superior mirage: inverted images
Sechrist, R.S., R.W. Fett, D.C. Perryman. 1989, Forecasters Handbook for the Arctic.
Naval Environmental Prediction Research Facility, Monterey, CA 93943-5006.
Technical Report TR 89-12.
Pekka Parviainen, University of Turku, Finland
The superior mirage: “stooping” images
Daniel Harnos, Princeton University
The superior mirage: multiple or complex images
floating ships
The Fata Morgana
King Arthur’s half-sister, Fata
Morgana in Italian, was a fairy
enchantress trained by Merlin the
Magician. She lived in a crystal
palace beneath the water and could
build fantastic castles from thin air.
photo by Robert Greenler
The ice in this photo is completely flat. Photo taken
in Antarctica (http://www.travelblog.org/Bloggers/ratzeputz)
Partial solar eclipse sunrise mirage
photo by Michael Gill
Sunset mirage with green flash
photo by Florian Schaaf
Another green flash
photo by Andy Young, San Diego State University
Ducting
photo by Laurent Laveder
More ducting
photo by Michael Slezak