Digieffects, a developer of visual effects software plug-ins, has
announced that Atmosphere (http://digieffects.com/product/atmosphere)
is available for purchase for US$49. The Atmosphere plug-in for After
Effects simulates atmospheric conditions such as haze and fog in your
composition.

Layers further away from the camera appear to be more deeply immersed
in the haze/fog than layers closer to the camera. This also applies
to parts of layers: if one edge or area of a layer is closer to the
camera, this area will appear less immersed in the haze/fog than the
pixels further away. You can simulate very realistic or very
unrealistic types of atmospheric effects using the Atmosphere
plug-in, according to Robert Sharp, president of Digieffects, ”

For $229 (a $19 savings) you can get Trapcode Lux and Atmosphere
bundled together. Lux is a stylistic aid that adds volumetric
lighting effects to projects that require realistic spotlights, point
lights, or stage lighting of all kinds.