Connections between PV Intrusions and Tropical Convection

Deep convection has been observed to occur at the leading edge of high-PV tongues intruding into the subtropical upper troposphere, and it has been suggested that these tongues initiate and support the convection by destabilizing the lower troposphere and causing upward motion ahead of the tongues. We investigate these using version 3 of the Penn State / NCAR MM5 mesoscale model. Two main questions are addressed: (1) What is the role of the PV in producing favorable conditions for convection?, and (2) What is the impact of latent heat release on the evolution of the PV? For the first question, we show that the presence of the high PV is of fundamental importance for the development of the convection. The high PV in upper levels causes increased CAPE, reduced static stability in the lower troposphere, and upward motion, which leads to convection. With regard to the second question, the MM5 results show that the interaction of PV tongue with latent heat can "produce" PV of the same order of magnitude as in the tongue, and alters the shape/structure of the tongue.