1,360
edits
Atmospheric light scattering: Difference between revisions
Jump to navigation
Jump to search
→Light scattering at dawn / dusk
| Line 89: | Line 89: | ||
Another effect which is currently not addressed adequately is the inter-cloud shading (clouds casting shadows on other clouds). Due to the layer structure of clouds, at noon this is usually not a big issue and only the self-shading of clouds is relevant, but for a low sun inter-cloud shading (and fog being shaded by clouds) is often very pronounced in reality. | Another effect which is currently not addressed adequately is the inter-cloud shading (clouds casting shadows on other clouds). Due to the layer structure of clouds, at noon this is usually not a big issue and only the self-shading of clouds is relevant, but for a low sun inter-cloud shading (and fog being shaded by clouds) is often very pronounced in reality. | ||
Contrary to common misconceptions, the sky itself doesn't necessarily become red-orange for a low sun - a clear sky remains usually dark blue, changing to light blue. The elements visible during a sunrise are: | |||
* Rayleigh scattering in the upper atmosphere, coloring the sky itself red if dust or aerosols are present (for instance after a volcano eruption or in a region with polluted air) - this is almost absent in clean air | |||
* Mie scattering of red-orange Rayleigh light in the lower atmosphere - this specifically creates a red-golden halo around the rising sun and is absent when looking away from the sun | |||
* Diffuse scattering of red-orange light in the ground haze fog - this contribution colors all directions almost equally, it can also be seen by a viewer facing away from the sun. | |||
* Clouds being illuminated by red-orange light - high clouds are translucent and can be seen against the sun, lower dense clouds block the sunlight and appear dark against the sun, but bright looking away from the sun. Most spectacular sunset pictures show red-orange clouds glowing in front of a relatively dark clear sky. | |||