Refraction / Total internal reflection at air layers

When looking at a boundary layer between cold and warm air at a shallow angle, distant mountains, ships, or other objects appear distorted.  

In very clear air, green or blue flares can sometimes be observed at the edge of the sun. A green flash is usually seen for only a fraction of a second, usually when the last bit of the sun disappears on the horizon.  

As the sun approaches the horizon, it is strongly deformed depending on the layering of the near-horizon air. For example, over water surfaces it often appears broad at the bottom or segments are pinched off at the upper edge of the sun.