CLOUD CLUSTERS, KELVIN WAVE CISK, AND THE MADDEN JULIAN OSCILLATIONS IN THE EQUATORIAL TROPOSPHERE

The Kelvin wave-CISK theory of the Madden-Julian oscillations in the t ropical troposphere is reexamined by introducing a phase lag between t he maximum cloud heating and the maximum convergence of the Kelvin wav e. The study was motivated by the observations in the equatorial Pacif ic that clouds in the Kelvin waves are organized into westward propaga ting mesoscale cloud clusters. Since this phase lag depends on the pro pagation speed of the Kelvin waves, the waves become dispersive, and t his leads to a favored growth of long waves. The results of this study suggest that the presence of organized mesoscale cloud systems needs to be parameterized directly into those climate models that cannot ade quately describe their dynamics.