For the land surface types, most notable are the differences between dry and wet surfaces, as well as the effects of snow cover and precipitation. Dry surfaces tend to have the highest emissivities and brightness temperatures, only slowly cooling with increasing frequency as emissivity gradually decreases. Adding water to a land surface decreases the emissivity, increases the scattering, and, therefore, cools brightness temperatures when compared to dry land. Further cooling of observed brightness temperatures occurs when dry snow cover and even light to moderate precipitation is introduced. Notice how this cooling becomes more pronounced at the higher frequencies.

Cooling of the observed brightness temperatures is further evidence of the scattering effect that results from the presence of ice in clouds and snow on the ground. Scattering increases with increasing frequency and is an important factor in determining precipitation over ocean and particularly over land.