THE VERTICAL STRUCTURE OF DIABATIC HEATING ASSOCIATED WITH THE MADDEN-JULIAN OSCILLATION SIMULATED BY THE GODDARD LABORATORY FOR ATMOSPHERES CLIMATE MODEL

Previous studies have shown that numerical simulations of the Madden-J ulian oscillation (MJO) are very sensitive to the vertical distributio n of diabatic heating. Since atmospheric diabatic heating is generally difficult to estimate, the vertical diabatic heating profile associat ed with the MJO is not well known. Judged by its propagation propertie s and spatial structure, the MJO is reasonably well simulated by the n ine-layer Goddard Laboratory for Atmospheres (GLA) general circulation model. Although only a simulation the model MJO may provide an indica tion of the vertical diabatic heating profile associated with the real oscillation. The diabatic heating structure of the model MJO is illus trated with composite charts made for those times when this low-freque ncy mode reaches its maximum and minimum amplitudes. These composite c harts compare the vertically integrated diabatic heating with potentia l functions, the vertical distribution of diabatic heating with the ea st-west mass flux function in the tropics, and the vertical profiles o f diabatic heating at the centers of maximum and minimum MJO amplitude . Three interesting features of the model MJO's diabatic heating are r evealed: (1) the maximum heating rate of this low-frequency mode is lo cated over the Asian monsoon region and its amplitude is about a half of the maximum value of the seasonal mean heating rate in this region, (2) the vertical diabatic heating rate profile has a maximum at 500 m bar and resembles the seasonal mean total heating profile, and (3) the total diabatic heating is for the most part composed of the latent he at released by cumulus convection.