A new month has started and conditions have been excellent for producing mirages. Several storm fronts have moved through the area rather quickly and over riding temperature layers have led to some spectacular mirages.
Morning Skyline to the East, Superior and Fata Morgana mirages.
First of all, what's a mirage? They are real phenomena of atmospheric optics, caused by strong ray-bending in layers with steep thermal gradients. Because mirages are real physical phenomena, they can be photographed. In a mirage, there is at least one inverted image of some object.
Often a mirage contains multiple images, alternately erect and inverted. Mirages are classified according to the number and relative positions of these images. The classical mirages are:
# of Images Name Description
2 Inferior mirage Inverted image below erect one
2 Superior mirage Inverted image above erect one
3 3-image mirage Inverted image between erect one
3+ Fata Morgana complex alteration of distorted erect and inverted images
The surrounding lights lifted up in a complex Fata Morgana mirage in the cold morning air. The mirages are caused by a sharp temperature inversion.
We continue to have great conditions for mirages. I have posted another photo today, taken this morning of village lights 23 miles away. The lights are lifted up in five layers and you can see some of the bending of the refraction layers in the top two layers.
Above is another shot of mirages to the NE of us with objects in the Kuparuk Oilfield lifted up.
A good example of a Superior Mirage, CD North drill rig.
*A superior mirage occurs when an image of an object appears above the actual object, due to the refraction of light waves from the object down toward the eyes of the observer. Downward refraction occurs because air closer to the ground is colder, and therefore more dense, then air higher up. Superior mirages can take the form of looming, towering, and inversion, depending on the particular structure of the air column.
** The fata morgana is a complex mirage in which distant objects are distorted as well as elongated vertically. For example, a relatively flat river bank may appear to have tall cliffs and columns. The phenomenon occurs under much the same meteorological conditions as the superior mirage with inversion, and contains features of both towering and inversion.
What do you get when you combine a solar eclipse with a temperature inversion? Answer--a very strange Alaskan sunset. I took this picture from the Colville River Delta of Alaska's North Slope on March 18th 2007:
The crescent shape of the sun is caused by a partial eclipse--the Moon passed off-center in front of the sun on March 18th and 19th. This was widely seen from India, China, and the northern reaches of Alaska. The rest is a mirage....
Below is taken from spaceWeather.com when they ran the eclipse photo:
"Alaska is the place for strong mirages," explains atmospheric optics expert Les Cowley. "Often, layers of very cold air sit beneath warmer layers. Here the abnormal refraction has produced a distorted and strongly flattened partially eclipsed sun. The miraging temperature inversion layers can be seen crossing the sun and at each side."
"Conditions like these often produce green flashes," he adds, but so far no one has reported a flash to go with this eclipse.
Green flashes will be another topic covered in a future post.