Potential Sources of Hemispheric Energetic Asymmetry

Abstract

The global distribution of Earth’s energetic fluxes has been studied but is incompletely understood. Despite symmetric solar input to the Northern and Southern Hemispheres, the Northern Hemisphere emits more energy. This project examines the source of radiative imbalance. Three features of Earth’s climate system that might contribute to this imbalance are global landmass distribution, variation in cloud cover, and differences between the polar regions. The larger landmass in the Northern Hemisphere causes differences in the surface reflectivity and quantity and type of clouds in either hemisphere. Variation in cloud cover of the hemispheres results from large physical features, including the Intertropical Convergence Zone and subtropical deserts. Finally, the disparate albedos, temperature ranges, and energy balances of the North and South Poles may contribute to radiative imbalance. This project uses CERES data, collected by NASA’s Earth Observing System, to study incoming and outgoing radiative fluxes. When the energetic balances are integrated from equator to poles, one can eliminate landmass distribution as a source of asymmetry; global differences in albedo caused by landmass distribution appear to be offset by cloud cover, adding hemispheric symmetry. The effects of specific features, such as the Intertropical Convergence Zone and subtropical deserts, are neutralized by cloud interactions in both longwave and shortwave radiation, and are not a major source of the imbalance. Overall, the results suggest that uneven energy transport into the polar regions drives the difference in radiative balances, causing more Arctic emission, a discrepancy likely related to physical features of the Arctic and Antarctic.