Northward movement of the 30-50 day mode in an axisymmetric global spectral model

Abstract

We have used an axisymmetric version of a 5-level nonlinear global spectral model to study the meridional propagation of convective zones, with an aim to understand the movement of the equatorial 30–50 day mode in the Indian monsoon region. The monsoonal type of circulation is caused due to the north–south differential heating in the Indian subcontinent. We have modelled the evolution of perturbations superposed on this basic flow. When cumulus heating (CISK) is included it is found that the cloud zones migrate northward. Our calculations show that the northward speed is about 0.5° per day.