Hemispheric Asymmetry of Land-ocean Distribution Causes Asynchronous Global Atmospheric Energy Response to Solar Forcing

The variation between Earth’s perihelion and aphelion causes seasonal fluctuations in the total solar radiation (SR) received by the planet. Our analysis of observational data and Community Earth System Model (CESM) simulations indicates that the temporal phase of atmospheric total energy in each hemisphere tends to follow the annual cycle of SR in each hemisphere with a delay of less than a month. However, the amplitude of the annual cycle of atmospheric energy in the Southern Hemisphere (SH) is weaker than that in the Northern Hemisphere (NH), despite the annual cycle of SR in the SH being 7% stronger than that in the NH. The stronger annual cycle response of atmospheric energy in the NH, despite its weaker annual cycle of SR, results in a six-month delay in the annual cycle of the global mean total atmospheric energy relative to the annual cycle of total SR received by Earth, as shown in both observations and CESM simulations. An aqua planet climate simulation reveals that the global and hemispheric mean atmospheric total energy in each hemisphere follows the SR annual cycles in both timing and amplitude. The contrast between the CESM and aqua planet simulations indicates that the difference in land-ocean distribution between the two hemispheres causes the asynchronous global atmospheric energy response to SR forcing. Using a dry radiative-convective coupled atmosphere-surface climate model, we confirm that this asynchronous global atmospheric energy response to SR forcing is driven by the hemispheric asymmetry in land-ocean distribution.