On the relationship between radiative entropy and temperature distributions

Abstract

The energy balance equation provides an important constraint on the distribution of outgoing radiation since the net global energy exchange will be close to zero over some appropriately long time interval. The entropy of the radiation does not obey such a conservation law, instead the outgoing entropy irradiance is much greater than the incoming amount. If the entropy irradiance is calculated with sufficient precision, it is possible to relate it to the distribution of radiative temperature over position, direction, wavenumber and polarization spaces. The radiative entropy decreases as the variance of the radiative temperature distribution increases over any of the four spaces listed above, under the constraint of a constant total irradiance. A uniform temperature distribution produces the maximum entropy flux for a given energy flux. Time series of the global outgoing longwave entropy irradiance is shown to be significantly different from the global outgoing longwave radiation, even though the calculations are derived from the same data. -from Author