Wave dynamics of super cloud clusters over the tropical region

A wave dynamics for the super cloud clusters associated with the tropical i ntraseasonal oscillation is constructed. Under the present framework, the b asic state of super cloud clusters is considered to be a large-scale conver gence of the zonal wind. This convergence is created by a nonlinear diabati c Kelvin wave front, which moves eastward slowly without change of shape. W hen interacting with free equatorial waves with n = -1, 0, 1 and 2, this ba sic flow will suppress those waves which move eastward except for free Kelv in waves, and permit westward propagating modes such as the mixed Rossby-gr avity wave, the inertio-gravity waves with n = 1 and 2 to appear in the lar ge-scale convergent region. Among these waves, only fast modes, that is, in ertio-gravity waves with n = 1 and 2 are regarded to be responsible for the presence of cloud clusters which move westward within a super cloud cluste r, while the multiplicity of the occurrences of super cloud clusters, which move eastward within the large-scale convergent region, is due to the supe rposition of free Kelvin wave upon these inertio-gravity waves. (C) 2001 El sevier Science B.V. All rights reserved.