Numerical modeling of orbit-spin coupling accelerations in a Mars general circulation model: Implications for global dust storm activity

• Published in: Planetary and space science 2017-07, Vol.141, p.45-72
• Main Authors: Mischna, Michael A., Shirley, James H.
• Format: Article
• Language: English
• Subjects: GCM; Global dust storm; Mars; MarsWRF; Orbit-spin coupling; Surface stress
• ISSN: 0032-0633; 1873-5088
• DOI: 10.1016/j.pss.2017.04.003

We employ the MarsWRF general circulation model (GCM) to test the predictions of a new physical hypothesis: a weak coupling of the orbital and rotational angular momenta of extended bodies is predicted to give rise to cycles of intensification and relaxation of circulatory flows within atmospheres. The dynamical core of MarsWRF has been modified to include the orbit-spin coupling accelerations due to solar system dynamics for the years 1920–2030. The modified GCM is subjected to extensive testing and verification. We compare forced and unforced model outcomes for large-scale zonal and meridional flows, and for near-surface wind velocities and surface wind stresses. The predicted cycles of circulatory intensification and relaxation within the modified GCM are observed. Most remarkably, the modified GCM reproduces conditions favorable for the occurrence of perihelion-season global-scale dust storms (GDSs) on Mars in years in which such storms were observed. A strengthening of the meridional overturning circulation during the dust storm season occurs in the GCM in all recorded years with perihelion-season global-scale dust storms. The increased upwelling produced in the southern hemisphere in southern summer may facilitate the transport of dust to high altitudes in the Mars atmosphere during the dust storm season, where radiative heating may further strengthen the circulation. Significantly increased surface winds and surface wind stresses are also obtained. These may locally facilitate dust lifting from the surface. Based on comparison to the historical record, there is a strong likelihood of a perihelion-season GDS in Mars year 33 and/or Mars year 34. •An orbit-spin coupling hypothesis may elucidate Mars dust storm activity.•Intensified circulation observed in all past years with perihelion season storms.•Enhanced surface stresses are coincident with intensified circulation.•Model suggests conditions well-suited to a global storm in Mars year 33 and/or 34.