Clarifying the role of hydrodynamic instability in the evolution of african easterly waves

Instability of the internal mid-level jet is revisited in light of recent studies that have questioned this long-standing paradigm for the origin and amplification of African easterly waves. In particular, these recent studies have suggested that the easterly jet is only marginally unstable and is too localized for waves to amplify sufficiently. These criticisms have merit given that the traditional approach has relied on normal mode instability of a zonally homogeneous jet. In this study, we explore alternatives to the traditional approach. We examine non-normal mode instability of a localized easterly jet and the role of moist convection in modifying the instability. We also further examine the potential for spatial instabilities (e.g., convective and absolute) in mediating the origin and intermittent nature of the waves.