Stratospheric Intrusions into the Tropical Troposphere

Using meteorological analyses and shallow water model simulations we examine the dynamics of Rossby wave breaking on the sub-tropical tropopause. We focus on wave breaking events that lead to an intrusion of high potential vorticity (stratospheric) air into the tropical upper troposphere. The occurrence of these events are shown to be sensitive to the basic state, and in particular zonal variations in the flow. This sensitivity results in strong seasonal and inter-annual (ENSO) variations in the frequency of these intrusions. We also examine the link between the intrusions and the occurrence of deep convection. In particular, PV inversion calculations to determine the vertical motion attributable to the anomalous PV within the intruded tongues of stratospheric air.