Irregularity: a fundamental property of the atmosphere*

Some early ideas concerning the general circulation of the atmosphere are reviewed. A model of the general circulation, consisting of three ordinary differential equations, is introduced. For different intensities of the axially symmetric and asymmetric thermal forcing, the equations may possess one or two stable steady-state solutions, one or two stable periodic solutions, or irregular (aperiodic) solutions. Qualitative reasoning which has been applied to the real atmosphere may sometimes be applied to the model, and checked for soundness by comparing the conclusions with numerical solutions. The implications of irregularity for the atmosphere and for atmospheric science are discussed. DOI: 10.1111/j.1600-0870.1984.tb00230.x