ON WAVE CISK AND THE EVAPORATION WIND FEEDBACK FOR THE MADDEN-JULIAN OSCILLATION

The combined effects of Kelvin wave-CISK and the evaporation-wind (E-W ) feedback are proposed as possible mechanism for the Madden-Julian os cillation. A very simple single,vertical mode model has been employed to examine the effects of both these processes on moist Kelvin waves. The effects of wave-induced moisture convergence is parameterized by r educing the moist static stability, and CISK occurs when the moist sta tic stability becomes negative. The E-W feedback in the presence of me an easterlies leads to unstable Kelvin modes. The presence of mean wes terlies leads to decaying Kelvin modes. When CISK and the E-W feedback work in concert, an unstable Kelvin mode develops that has phase spee ds of propagation between 5 m s-1 and 10 m s-1 for a large range of pa rameter values. On the other hand, the E-W feedback mechanism alone, i n the case when CISK is not operating, produces the phase speeds of th e observed Madden-Julian oscillation for only a very limited range of parameter values.