Friday, March 25, 2011

Super Moon in Mirage

After a mostly overcast February, March has presented us with lots of clear skies and  the sun is up for over 12 hours (pasted the 12 hour mark on the 18th)  now and generates a nice amount of heat during the day.  This has also lead to many days with superior mirages, both at night and during the day light hours.

Mirages and distortions are produced when the rays of a low sun or moon pass through atmospheric regions where there are strong temperature gradients. Temperature per se has no direct effect but a vertical temperature gradient is also a density gradient.

The strong  inversion layers created some spectacular images of this months full moon, which also happened to be  what is called a “Super Moon”, or a super “Perigee Moon”.     Full moons very in size depending on where in the moons elliptical  orbit around the earth it is. This months full moon coincided with the its orbit being  within one hour of perigee, or the closest it comes to earth.  Being this close to the actual perigee event only happens about every 18 years.  When it is at perigee it is about 50,000 km closer to earth than when it is at apogee (farthest away) and is about 14% larger, and 30% brighter than the more normal full moons.

The full moon occurred on March 19 this year and this posting is to share several photos of the moon  a couple days around full, both in the day time and at night.

Almost full Moon-March_6930



Photo on left from March 17 at 7 PM AST.



       Setting SuperMoon-mirage_6947


Photo on right     shows moon setting on the 18th being   affected  by inversion layer, also a touch of green on the upper edge.





Moon rise over the Kuparuk Oilfield at 7 PM on the 18th.





       Moon setting morning of the 19th through thin layer of clouds. The bottom of the moon is starting to be affected by a inversion layer , thus the distorted effect.




  This photo is one of my most dramatic in regards to the amount of distortion to a moon I have seen in all my years in the Arctic.  

  This strong mirage effect is explained by atmospheric expert Les Cowley.  "This is a very strong mirage produced by rays bent while crossing intense vertical temperature gradients between a layer of cold air beneath warmer air. The lunar disk details are vertically stretched, suggesting that the mirage is part of a fabled Fata Morgana.  

It is an extreme and complicated variant of a superior mirage and called a "Fata Morgana" after the fabled Morgana, enchantress half-sister of King Arthur. The mirages are perhaps views of her island palace. The Morgana needs a temperature inversion, warmer air above cooler, with temperature gradients in parts increasing strongly with height. Then, several rays from a relatively low lying object or even the ground are all curved towards the eye giving the impression that the object is smeared upwards. In reality the Morgana is more complicated with parts inverted and stepped. The temperature inversions making them are not simple and may also have waves that cause different mirage sections to vary in height. Although the Morgana might be seen anywhere it mostly occurs during very cold weather or in Arctic regions where heavy frigid air overlays the ground.


This video has a whole series of moon mirage pictures taken at the same time as the marshmallow shaped moon picture posted above.

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Arctic Smoke Signals by James W. Helmericks is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.