The intertropical convergence zone (ITCZ) is observed to undulate and break down into a series of disturbances on the timescale of a few days. This process is referred to as "ITCZ breakdown". ITCZ breakdown may be one of the possible mechanisms to pool vorticity in the tropical atmosphere to form tropical disturbances which represent the early stages of tropical cyclone genesis. A series of papers (Hack et al. 1989; Schubert et al. 1991; Guinn and Schubert 1993; Nieto Ferreira and Schubert 1997) have proposed that latent heat release in deep convection in the ITCZ is the process initiating ITCZ breakdown.

The barotropic aspect of ITCZ breakdown has been simulated by using a global nonlinear shallow water model (Nieto Ferreira and Schubert 1997). Our research extends their work by using a primitive equation (PE) model which includes vertical structures in simulating ITCZ breakdown. An imposed heating, which is centered at 10°N, is turned on for 5 days at the beginning of the simulations. A positive potential vorticity (PV) anomaly develops on the poleward side below the level of maximum heating on the second day of the simulation. At upper levels, a weaker negative PV anomaly develops on the equatorward side. Two types of sensitivity experments are examined. The first type examines the different heights of maximum heating. It shows that the lower the height of maximum heating, the stronger the PV anomaly at the lower level. However, the vertical location of the PV anomaly does not change too much, and the breakdown of the PV strip is only accelarated slightly. The second type of sensitivity experments uses different heating rate with the maximum heating fixed at 650 hPa. Stronger heating rates generate stronger PV anomalies, and the PV strip breaks down significantly faster.

The sensitivity of ITCZ breakdown to different background flows such as the trade winds will be examined.