Abstract
With the very high horizontal resolution (T63 and T159), an aqua-planet version of the JMA operational global model was integrated. For both resolutions, the Madden Julian (M-J) oscillation with the period of 40 days has appeared. The structures with the scale of zonal wave number one in two different resolution models are nearly identical, while the amplitude of the M-J oscillation in the T159 model is two times larger than that in the T63 model. To the east of the equatorial convergence in the lower troposphere, moist convective systems are mainly found in the equatorial region, while to the west of the convergence, convective systems are found in the off-equatorial tropics. Moisture budget analysis indicates the importance of frictional convergence near the surface for the maintenance of the M-J structure.In the T159 model, the ensemble of cloud clusters (a super cloud cluster) behaves similarly to that in the nature analyzed by Nakazawa (1988). However, the scale separation between the M-J oscillation and the super cloud cluster is not obtained in our model.We examine the influence of the M-J oscillation upon the generation of tropical cyclones. A large number of tropical cyclones are generated near or near-west of the equatorial lower convergence associated with the oscillation. These cyclones contribute to the formation of a symmetric Rossby wave structure elongated in the zonal direction.
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