Diagnosis of African Easterly Wave Structure and Development using Quasi-Geostrophic Potential Vorticity

Despite their acknowledged role in the formation of Atlantic hurricanes, African Easterly Waves (AEWs) remain enigmatic features of the atmospheric flow over the tropical Atlantic Ocean, as fundamental questions regarding their structure, underlying dynamics, and potential for transition into tropical cyclones remain unanswered. This research seeks to characterize the structure and dynamics of AEWs from the perspective of quasi-geostrophic potential vorticity (QGPV) using high-resolution, global atmospheric analyses. We have demonstrated that this method is a practical approach for accurately representing AEWs throughout their life cycle. The project endeavors to identify, using QGPV wave composites, the characteristic PV structure of these waves at various times spanning the AEW life cycle, and then to relate this structural evolution to the evolution of the corresponding wind and thermal fields. The second phase of the project then involves analysis of how the deformation of the flow on larger scales affects the changing PV structure. Compaction of PV anomalies into a more isotropic disturbance due to mean flow deformation serves to increase its kinetic energy, a mechanism that may alone be responsible for the initiation of tropical cyclogenesis. The results of the proposed work will provide necessary tools for the identification of both the geographical regions and the specific wave structures that are best suited to promote AEW tropical cyclone development.