Axisymmetric Steady Solutions in an Idealized Model of Atmospheric General Circulations : Hadley Circulation and Super-rotation

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Fundamental dynamics of two-dimensional atmospheric general circulations symmetric about the rotation axis of planets is investigated to obtain a wide perspective from the Held and Hou model of the Hadley circulation to the Venus-like super-rotation driven by the Gierasch mechanism.A parameter sweep experiment is performed to explore steady solutions of the axisymmetric primitive equations of the Boussinesq fluid on a rotating sphere. Sweep parameters are the external thermal Rossby number (RT), the horizontal Ekman number (EH), and the vertical Ekman number (EV). Two indices are introduced to make a dynamical analysis of the numerically obtained circulations: a measure of the intensity of super-rotation (S) and a measure of rigid rotation (Rg). The characteristics of steady solutions change largely in a certain range of EH for given RT and EV. Approximate positions of this transition can be estimated theoretically as EH∼ EV S(RT), where S∼ RT for RT ≤ 1 and S ∼ √RT for RT > 1.
日本学術会議「機械工学委員会・土木工学・建築学委員会合同IUTAM分科会」の論文