Abstract : The time variation of the atmospheric radiation regime is investigated for a selected synoptic situation. Elsasser's graphical method shows the diurnal variation of the upward-directed longwave flux to be in phase with surface temperature changes, but no such change of downward flux was found. Clouds reduce the upward flux above the cloud tops and increase the downward flux below their bases. Long-wave radiative cooling is greatest above cloud tops and at upper surfaces of inversions. Ground surface temperature is shown to be very important in the long-wave regime. Short-wave molecular scattering and surface reflection are evaluated for a model atmosphere by Chandrasekhar's exact method and are adapted for the synoptic situation. Water vapor absorption, ozone absorption, and the effects of atmospheric dust are approximated. Surface reflection, water vapor absorption, and absorption by particulates in a polluted atmosphere all play dominant roles, while the effects of molecular scattering and ozone absorption are relatively minor in the over-all energy regime.