Abstract

Observational estimates of global top-of-atmosphere radiation on monthly, seasonal, annual, and longer time-scales require estimates of the diurnal variability in insolation and the asymmetry of surface and atmospheric reflection. We compare EPIC and NISTAR observations from the DSCOVR satellite with CERES hourly synoptic fluxes, which are filled through geostationary observations, and find that a Fourier analysis of these data substantially agree, showing strong relative power at sub-diurnal, diurnal, seasonal, and annual time-scales, and power growing from diurnal to seasonal time-scales. Frequency analysis of fluxes from several models shows that they distribute too much power over periods greater than 1 day but less than one year, indicating that a closer look is needed into how models achieve longer-term stability in reflected shortwave radiation. Model developers can consider using these datasets for time-varying energetic constraints, since tuning parameter choices will impact modeled planetary shortwave radiation across timescales ranging from sub-diurnal to decadal.