cloud radiative forcing

The difference between net irradiances measured for average atmospheric conditions and those measured in the absence of clouds for the same region and time period.

Cloud radiative forcing depends jointly on the amount of cloud present and the sensitivity of radiation to cloud amount. It may be partitioned into longwave and shortwave forcing terms, the combination of which typically results in a negative net forcing when referenced to the top of the atmosphere (i.e., satellite measurements). That is, a clear region typically reflects less solar, and emits more terrestrial, radiation than does the average condition, and the difference in solar reflection is typically greater than the difference in terrestrial emission to space. While the definition of cloud radiative forcing in terms of average measured values is unambiguous, the relationship between cloud radiative forcing and the equilibrium effects of clouds on climate, especially on surface temperature, is a complicated topic.
See also radiative forcing.

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.

The difference between net irradiances measured for average atmospheric conditions and those measured in the absence of clouds for the same region and time period.