Impact of variations of gravitational acceleration on the general circulation of the planetary atmosphere

- The planet's gravity determines the meridional structure of atmospheric circulation.
- An energy cycle analysis reveals the major drivers of the atmospheric circulation.
- With increasing gravity the meridional circulation changes from 3 cells to 1 cell.

Fundamental to the redistribution of energy in a planetary atmosphere is the general circulation and its meridional structure. We use a general circulation model of the atmosphere in an aquaplanet configuration with prescribed sea surface temperature and investigate the influence of the gravitational acceleration g on the structure of the circulation. For g=g0=9.81ms−2, three meridional cells exist in each hemisphere. Up to about g/g0=1.4 all cells increase in strength. Further increasing this ratio results in a weakening of the thermally indirect cell, such that a two- and finally a one-cell structure of the meridional circulation develops in each hemisphere. This transition is explained by the primary driver of the thermally direct Hadley cell: the diabatic heating at the equator which is proportional to g. The analysis of the energetics of the atmospheric circulation based on the Lorenz energy cycle supports this finding. For Earth-like gravitational accelerations transient eddies are primarily responsible for the meridional heat flux. For large gravitational accelerations, the direct zonal mean conversion of energy dominates the meridional heat flux.