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We employ the MarsWRF general circulation model (GCM) to test the predictionsof a new physical hypothesis: a weak coupling of the orbital and rotationalangular momenta of extended bodies is predicted to give rise to cycles ofintensification and relaxation of circulatory flows within atmospheres. Thedynamical core of the GCM has been modified to include the orbit-spin couplingaccelerations due to solar system dynamics for the years 1920-2030. Themodified GCM is first subjected to extensive testing and validation. We compareforced and unforced model outcomes for large-scale zonal and meridional flows,and for near-surface wind velocities and surface wind stresses. The predictedcycles of circulatory intensification and relaxation within the modified GCMare observed. Most remarkably, the modified GCM reproduces conditions favorablefor the occurrence of perihelion-season global-scale dust storms on Mars inyears in which such storms were observed. A strengthening of the meridionaloverturning (Hadley) circulation during the dust storm season occurs in the GCMin all previously known years with perihelion-season global-scale dust storms.The increased upwelling produced in the southern hemisphere in southern summermay facilitate the transport of dust to high altitudes in the Mars atmosphereduring the dust storm season, where radiative heating may further strengthenthe circulation. Significantly increased surface winds and surface windstresses are also obtained. These may locally facilitate saltation and dustlifting from the surface. The numerical simulations constitute proof of conceptfor the orbit-spin coupling hypothesis under evaluation.

Numerical Modeling of Orbit-Spin Coupling Accelerations in a Mars General Circulation Model: Implications for Global Dust Storm Activity