African Easterly Waves and convection

In this research the physical mechanisms relating synoptic scale African Easterly Waves (AEWs) and convection are explored using a variety of analysis techniques.;This work begins with the formulation of a new set of objective diagnostics for the identification and analysis of AEWs in gridded datasets. This is forced by the lack of a standardized framework for the analysis of these systems analogous to those used in mid-latitude meteorology. These tools and techniques are used to examine the AEWs generated over the African continent during July-September 2004, 2005 and 2006, including their spatio-temporal relationship with organized convection. These diagnostics are also employed to examine the representation of AEWs in numerical weather prediction (NWP) models and how varying the sub grid scale parameterization of convection in NWP models impacts the forecasts of synoptic AEWs. It is observed that NWP models exhibit downstream drift in synoptic activity, have difficulty in emulating the observed phase relationship between AEWs and convection, and also that forecast AEWs are sensitive to how convection is parameterized.;The major portion of this dissertation is devoted to a process study of an AEW conducted using a full-physics mesoscale model. This work finds that both adiabatic and diabatic processes are equally important in generating eddy available potential energy in the growth of the AEW. Using a perturbation experiment where moist process are absent, the secondary role of convection, whereby potential vorticity (PV) anomalies are diabatically generated is shown to be integral part of the AEW dynamics. The nature of these PV anomalies is further examined using a cloud resolving model, which demonstrates that these features are associated with the different convective and stratiform heating profiles present in a typical West African squall line and that these are well represented by physical parameterizations. The mechanisms responsible for the observed spatio-temporal relationship between AEWs and convection are explored. Unlike previous research, is it suggested that thermodynamic factors (cold core of AEW) are more influential than dynamic (e.g. isentropic motion) factors in governing this relationship.