Journal of Geophysical Research, submitted 8/07.

# Instability of the axisymmetric monsoon flow and intraseasonal oscillation

Gilles Bellon
Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY.

The mechanisms of propagation and reinitiation of convection are further described. The off-equatorial mechanism responsible for the northward propagation involves the creation of barotropic vorticity north of the convection center by baroclinic advection of baroclinic vorticity. This barotropic vorticity in turn creates low-level convergence via Coriolis acceleration, and subsequent convection. The mechanism responsible for the reinitiation of the convection at the equator involves the creation of barotropic easterlies by baroclinic advection of baroclinic zonal momentum. These barotropic easterlies in turn generate low-level convergence via the $\beta$ term of the Coriolis acceleration, and subsequent convection.