Superior mirages & Fata Morgana…

Superior mirage of a ship that is “below” the horizon, at cape Sounion.


We went to Sounion for another reason (Super full Moon), and finally another we saw (and not broke down at all). Fata Morgana well… you will have heard the term, but let’s see, what atmospheric optical phenomenon is used.

A different term that we could use instead of the Fata Morgana, is, perhaps, the “multiple superior mirage”. A lot of people use the term Fata Morgana for irregular figures, sometimes, if the conditions are right, make their appearance in the far sea horizon (for the corresponding legend that accompany this condition, you can read here) and usually exhibit and deformation as time passes.

The Fata Morgana belongs to the superior mirages, the mirages those that are created when there are specific atmospheric conditions, where the image is above the real object. However, in this particular case, because it is, more than one, idols, and deformed, has been given this particular name.

Many of you, perhaps you are familiar with inferior mirages (yes, you guessed it, are the ones where the image is formed under the real object), and in particular with those who look like “water” on hot asphalt, on a hot summer day.

How it is created, however, a superior mirage (without going into too much details); To help a little, it’s good to have an image in our mind. Let’s say a ship at sea which we observe while we sit on the beach. If the boat is traveling away from us and eventually pass the event horizon, then we cease to see it. This is because each light ray that starts from the boat travels straight (or almost straight), with the result that it passes over us and our eyes (since it is below the horizon). In short this means that “we don’t have visual contact” with the boat.

There is a case to see if it is below the horizon? Yes. And to do this, we must, in some way, the luminous rays which start from the boat to NOT travel straight, but to turn, following the curvature of the Earth, so that they reach our eyes.

And how does this “magic” to you? Here comes the role of the “specific atmospheric conditions” that we mentioned before. These particular conditions are called “temperature inversion”, i.e., the lower tropospheric layers to be colder the higher (in short, not dropping the temperature by height, as is usually the case, but the opposite of a point and over and for some measures! So there is a warm layer above us, while we are within the colder layer).

And how is that helpful? The warm air is αραιότερος and when a light beam enters from a colder (and denser) layer to a warmer (and αραιότερο), then “turns”. And turns so much that after a point it becomes “total reflection”. So it’s like there’s a “mirror” in the sky that shows us what is below the horizon (the ship). See the following figure in which have overdramatized the curves and sizes, so that it becomes obvious the general mechanism for the creation of the upper mirror.

Now, the Fata Morgana, it just happens, when the layer plays the role of a “mirror” and it is located between us and the warm layer higher up, is more complicated as regards temperature and humidity, with the result that there is more than one, points “total reflection” (i.e. more than one “mirrors”) and, therefore, more than one images (superior mirages).

Here some images of the phenomenon yesterday in Sounio. Notice on the left the deformed image and see a still very weak, even more to the left.

Superior mirages of many different ships. Note especially the distorted images on the right and how they change slightly in shape.

Of course this is not as impressive as other similar incidents, pictures of which can find someone looking to google. How impressive and clear it will be the phenomenon, depends on the thickness of the optical conductive” layer, which is a function of meteorological conditions as explained above. Source Athens Astrophotography & Storm Chasing Team

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