Here we add one more component to the peculiar nature of near-interhemispheric symmetry. We examine total accumulated rainfall (m3/day) as a function of time and season. Global rainfall varies between 0.1-1% between seasons. The annual accumulated precipitation between hemispheres varies by about 2% with greater precipitation occurring in the Southern Hemisphere. Over the globe, there is roughly three times more precipitation over oceans than land while the ratio between accumulated rainfall over land and ocean has remained essentially constant over the last three decades. This constancy has occurred while the surface temperature of the planet has increased, the area of the warm pool has enlarged and while, it appears, that the northern hemisphere is warming at a greater rate than the southern.
We examine what these curious near-symmetry may tell us about the evolving climate. Does it propose a fundamental constraint on climate? Does it help us understand why ice-ages and warm periods in the past occur globally even though the changes in orbital forcing that are thought to produce them are distinctly hemispheric! Do these near-symmetries provide us with a measure to test how well our climate models are simulating climate?
Stephens, G. L., D. O'Brien, P. J. Webster, P. Pilewski, S. Kato, and J.-l. Li (2015): The albedo of Earth, Rev. Geophys., 53, doi:10.1002/2014RG000449
Stephens G. L., Hakuba, M. Z., Hawcroft M., Hatwood J., Kay J. E., Webster PJ., 2016: The curious nature of the hemispheric symmetry of the Earth’s water and energy balances. Current Climate Change Reports (in press)