Superior mirage

Isokari lighthouse and pilots' house distorted

Isokari island is 14 kms away from my photography site. On the island there is a lighthouse which has three red and three white bands of equal width painted on it (see the reference picture on the first row). There is also a whitish sea pilots' house with some other buildings and f.ex. a white satellite dish next to it. This page shows superior mirages of those objects.

On the bottom of the page there are several composites of the lighthouse and of the pilots' house. In some images you can calculate up to seven red zones on the lighthouse while there actually is only three.

About superior mirages. A clear and 'good' superior mirage is far more rare than an inferior mirage. It is born when a surface of cold air is covered by a warm layer of air (so called inversion layer). On my observing site this may happen in late spring - early summer, when the sea is freed from ice and warm and dry air is blown over the cold water. This may create a steep thermal gradient (thermal gradient describes how temperature changes with respect to height), which is exactly what is necessary for a superior mirage to appear. Word 'superior' refers to the place of the mirage: miraging image appears above the 'true' object and is inverted. At large water surface the surface appears bowl shaped (convex), horizon line extends abnormally far away and 'strange' new islands may become visible. Superior mirage is also responsible of the famous 'Fata Morgana'.

A good superior mirage is much harder to detect and to witness than the common inferior mirage. First of all you need steep thermal gradient and also a good visibility. My experience is that the best superior mirage is usually seen at the distance of 10-20 kms. Every so often a superior mirage is evident but due to haze or excessive humidity the contrast is poor and sight is not too inspiring. This problem you can notice in several images on this page and also on other pages showing superior mirages. More problems arise f.ex. from films, which do not reproduce good contrast in strong UV-light and in bluish haze. Moreover, superior mirages are often short lived due to wind, which is born at shoreline and which very effectively mixes the inversion layer. However, a major obstacle in detecting superior mirage is the location of the observer. A good display can be visible at certain height, while vantage point one meter higher or lower shows hardly any miraging. In general this means that to witness this great atmospheric phenomenon, you have to have access to different heights to view the horizon. A pair of binoculars is a must in the search of superior mirage.

Superior mirage is far more interesting than inferior mirage. Object may be just stretched or squeezed vertically or it may be doubled and turned upside down. In some occasions a second miraging image may become visible (this time right side up) above the first miraging image. In some rare cases two more miraging images can be seen above the first two - and here again the first image upside down and the second right side up. (For better images see page 'Superior mirage'; on this page see f.ex.'sup22g41'.)

For a more comprehensive approach to the subject see Andew T. Young's great pages.