It was so cold, I could not see straight!
Sub-zero temperatures prevailed even in the intense sunlight. The sunlight warmed air above a ground layer of bitterly cold still air. This created a strong temperature inversion. Normally cold air resides above warmer air at ground level. Today it was the opposite. Optical turbulence was obvious from the inhomogeneous mixing of cold and warm air cells.
The warmth of my car added to the turbulence challenges. Swirls of warm air escaped the open window into the freezing air, blurring my vision. Light rays originating from my photography subjects were diverted en route to my camera.
When I researched optical turbulence in my past life, I likened these warm/cold air cells to lumps found in tapioca pudding.
Normally this kind of optical turbulence is associated with looking across the ground of a hot desert. In the heat of a summer day, hot air rises from the ground and interacts with cooler air above. Pockets of hot and cold air refract rays of light differently. What once was a light ray traveling straight through uniform temperature air was now diverted each time it encountered an air cell with a different temperature.
The resulting optical effect is much like looking through privacy glass used in showers – the image of the subject is blurred since there is no longer a one-to-one mapping from a point on the subject (scene) to a point on the camera sensor or my pupil. This makes photography challenging. It is impossible to get a sharp image. Atmospheric turbulence can blur photos and our vision in hot and cold environments.
I had experienced this effect photographing wolves in Yellowstone. It was a sunny day and no wind; the air temperature never rose above -27 deg F. I almost threw my new camera in the trash since it would not acquire a sharp focus. It was not an issue with the camera, though.
Another temperature inversion effect caused some bizarre optical effects in the frigid San Luis Valley.
Whereas the previous discussion described how intermixed pockets of warm and cold air scrambled light rays’ directions, resulting in a blurry image, the strong temperature inversion caused superior mirages to occur.
Known as Fata Morgana, these mirages “lift” distant mountains into the air, sometimes creating multiple inverted images above the real image.
The term Fata Morgana is the Italian name for “Morgan the Fairy”, a sorceress of medieval legends and sister of King Arthur. The legendary Fata Morgana has been blamed for causing complex mirages over bodies of water, especially in the Strait of Messina.
My trip into the deep freeze of San Luis Valley was otherwordly. Life feels delicate in these arctic conditions. The raptors I saw hung onto every calorie they could, resting on telephone poles to save their precious energy to stay warm and only fly when they saw prey down below.
Observing the bending of light rays in the extreme temperature inversion made me think about what I was seeing. It triggered memories of seeing snowy peaks dancing above the San Luis Valley floor, far north of Taos. Without the extreme temperature inversion, I cannot see these distant peaks.
It feels good to be home safely by the woodstove after my winter voyage!