Simulated variability in visible and near-IR irradiances in preparation for the upcoming Libera mission

NASA’s upcoming Libera mission is predominantly a continuity mission, aiming at the seamless continuation of the Earth Radiation Budget record maintained by CERES. It therefore provides CERES-characteristic measurements, but also innovative and added capability that allows to discern the visible (VIS) and near-IR (NIR) contributions to the deposition of shortwave radiation in the climate system. Main scientific areas and applications for Libera’s “split-shortwave” measurement are the improved understanding of processes that contribute to changes in shortwave absorption, a main contributor to sustained global climate change, and to study Earth’s albedo and hemispheric symmetry observed therein. Here, we use Earth System Model (ESM) output to characterize the variability in VIS and NIR irradiances and absorption under pre-industrial conditions and under abrupt 4xCO2 forcing. Similar to the NDVI, NIR/VIS ratios are indicative of the surface’s “greenness” and allow to track changes in surface cover and cloud effects. Global mean NIR and VIS irradiances elucidate on the role of surface albedo, water vapor and cloud feedbacks for curiously maintaining a NIR/VIS ratio near 0.8 for both the forced and unforced simulation. With multiple spectral shortwave missions on the way, approaches to exploit these novel datasets and to reduce uncertainty in observed and modeled radiative effects and feedbacks, is quintessential, especially because enhanced shortwave absorption will continue to play a major role in contributing to Earth’s energy gain currently observed and expected to increase under ongoing CO2 forcing.