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INTEGRATION: ATMOSPHERIC TURBULENCE

This study will go over the effects of atmospheric turbulence. I was inspired to look into this subject after trying to classify atmospheric phenomena I saw in E.T. as a part of my Spielberg study.

ATMOSPHERIC SEEING AND SCINTILLATION

Atmospheric seeing refers to atmospheric turbulence causing refraction of objects outside of our atmosphere. The effect is similar to heat haze.


Example from E.T.


This effect is related to twinkling stars.

When atmospheric turbulence affects stars, the term is: atmospheric scintillation. The effect is not evenly distributed in the the sky; it’s heaviest where there is more atmosphere:

“scintillation which is most evident to the naked eye as twinkling of point sources, particularly of the brightest stars. Twinkling… is strongest for stars close to the horizon”

- C. Sterken et al., Astronomical Photometry, A Guide

Because twinkling/scintillation is an effect of our atmosphere when viewing stars from Earth, the effect goes away when viewing stars from space. But twinkling can still be added for visual interest for shots not grounded in reality:


Scintillation and seeing can have different conditions in which they can appear:

”Since the refractive power of the atmosphere decreases with increasing altitude, and because the deviation increases linearly with distance, the source of seeing is likely situated nearer to the ground, while scintillation is produced at higher elevations above the ground.

Scintillation and seeing show little correlation: it is possible to have poor seeing together with negligible scintillation, but the reverse situation cannot occur.”

- C. Sterken et al., Astronomical Photometry, A Guide

TERRESTRIAL SCINTILLATION

How is the effect of thinking stars related to the twinkling of city lights?

“The flickering or twinkling effect of lights when observed from a distance is caused by anomalous refraction as light passes through air, schlieren, where temperatures and densities vary. The technical term for this phenomenon is called "scintillation," and it refers to the rapid changes in the position and color of a distant object.

If the light source lies outside the atmosphere of the Earth, such as the stars and the planet, the term for the flickering effect is called "atmospheric scintillation." When the source of illumination is Earth-bound, the phenomenon is referred to as "terrestrial scintillation."

Wind movements that are carrying schlieren flowing across an observer's line of sight causes the light fluctuations that are characteristic of the scintillation phenomena. Studies also show that relative humidity affects the intensity of terrestrial scintillation. As humidity increases, so does the effect of terrestrial scintillation.”

- reference.com, https://www.reference.com/science/lights-appear-flicker-distance-95bd632a84e4521

An example can be found in Heat. Notice how the effect increases with distance: