FUNDAMENTAL MOIST MODES OF THE EQUATORIAL TROPOSPHERE

Raymond's diabatic parameterizations are combined with a three-dimensi onal channel model on an equatorial beta plane. The equatorially symme tric moist modes of this model for an atmosphere initially at rest are ''nonlinear WISHE'' (wind-induced surface heat exchange) modes. These modes are driven by the enhanced sea-air fluxes of entropy produced b y self-generated westerly winds. Two varieties of these modes are foun d, those which move to the east at 8 m s(-1) and those which move to t he west at 4 m s(-1). In both modes heavy rain occurs in air that has been moistened by convection of low precipitation efficiency. This pre conditioning introduces a phase shift of several days between strong s urface entropy fluxes into an air column and the heaviest rainfall. Th is phase shift may be responsible for the relatively low modal propaga tion speeds compared to those seen in other models. The modes identifi ed in simulations with uniform sea surface temperature pray a fundamen tal role in a simulation with a warm-pool-like sea surface temperature anomaly. The authors tentatively identify the simulated modes with Na kazawa's ''superclusters.''