On the present and future of Earth Energy Balance measurements

Abstract: The upcoming Libera mission, NASA’s first Earth Venture Continuity selection, will provide seamless continuity to current broadband radiance measurements obtained by the Clouds and Earth’s Radiant Energy System (CERES) project since March 2000. Leveraging advanced detector technologies, Libera will measure the broadband total, longwave, and shortwave radiances akin to CERES and carry a fourth radiometer to measure shortwave near-infrared radiances to advance our understanding of processes relevant to shortwave absorption by the climate system, radiative feedbacks, and Earth’s albedo variability with added insight into hemispheric albedo symmetry. We use global model simulations and radiative transfer calculations to demonstrate applications of the added spectral knowledge in climate science. Although Libera’s absolute accuracy is unprecedented, closing Earth’s energy budget may still be a challenge and requires complementary methodologies. We will therefore discuss current and future avenues to measure Earth’s Energy Imbalance (EEI) indirectly and directly from space. Direct measurements are potentially feasible through sensing radiation pressure-induced accelerations acting on near-spherical spacecrafts, which under optimal conditions, are directly proportional to the net radiative flux experienced at the satellite’s location. This approach has been considered in the past, and the mission requirements to achieve sufficient measurement accuracy are currently under investigation. We will also discuss the critical need for maintaining Radiation Budget measurements, especially in the context of climate modeling, and the design and vision of a future constellation that would satisfy multiple challenges our community is facing related to improving our knowledge of EEI magnitude and change, and the spectral dimension of Earth’s energy budget.