African easterly waves in an idealized general circulation model: instability and wave packet diagnostics

Abstract. We examine the group dynamic of African easterly waves (AEWs) generated in a realistic, spatially non-homogeneous jet (AEJ) using an idealized general circulation model. Our objective is to investigate whether limited zonal extent AEJ impediment AEW development. construct series basic states global reanalysis fields and initialize via transient heating over West Africa. The dominant response localized, near-stationary wave packet that disperses upstream downstream. inclusion crude representation boundary layer damping stabilizes most cases, consistent with other studies past. In some states, however, exponential growth occurs even presence damping. This shows AEWs can occasionally emerge spontaneously. key result that, triggered by external forcing or internally, remain within for multiple periods instead being swept away. Drawing from studies, this also suggests damped grow if coupled additional sources energy such as moist convection dust radiative feedback. localized appears satisfy condition absolute instability, form spatial hydrodynamic instability. However, needs be verified more rigorously. conclude not impediment. results suggest intermittent nature mediated, transitions between convective but likely propagating equatorial modes.