Atmospheric scattering occurs when particulates diffuse the incident radiation. The size of the atmospheric particles and the wavelength of the incident radiation help determine what type of scattering happens.
Rayleigh scattering occurs when radiation interacts
with particles or molecules much smaller in diameter than the wavelength of the radiation.
The degree of Rayleigh scattering is inversely proportional to the fourth power of the wavelength.
As a result, short wavelength radiation tends to be scattered much more than long-wave radiation.
The appearance of the "blue" sky is a consequence of this type of scattering. Visible satellite
imagery is also suseptible to rayleigh scattering, especially looking with some component
towards the sun. The effect is a hazy image looking towards the sun as can be seen in the center of
this image. 
And a less than hazy image can be seen 
looking away
from the sun in the center of the second image above. These two images were taken over
Argentina and Chile. To reduce the haze effect, pick a longer wavelength such as the near infrared
channel aboard the AVHRR instrument on the
NOAA polar orbiting satellites. Note that even though the lower
image is brightened, the cloud free areas are still darker than the top image.
If the atmospheric particulates are of the same size as the wavelength of incident radiation, Mie scattering becomes important. This type of scattering can affect longer wavelength radiation. Smoke and dust particles are the dominant sources of Mie scattering. Again, as in Rayleigh scattering, most of the incident radiation is scattered in a forward direction.
Large atmospheric particulates like cloud droplets of 5 to 100 um in diameter interact with radiation, non selective scattering is the result. This kind of scattering affects all the colors in the visible and near infrared spectrum nearly equally. Clouds appear white because of this type of scattering as can be seen with the above two images.