Variability of African Easterly Wave Characteristics

While studies have shown the pronounced variability of African easterly wave (AEW) structure, intensity as well as wavelength, there lacks a thorough study documenting the spectrum of AEW behaviors. In this study, we conduct a survey on the variability of AEW characteristics with an AEW tracking scheme and explore the causes of the various behaviors.

The reanalysis data from ERA Interim is used. The tracking algorithm is an updated version from Brammer and Thorncroft (2015). The AEWs are tracked based on curvature vorticity and vorticity at multiple AEW active levels to ensure coherent wave structure and a broad spectrum of waves. The probability distribution of AEW characteristics such as phase speed, intensity and wavelength will be constructed.

The second half of the research will attempt to understand the causes of variability in wave characteristics. Three key factors will be considered, the environment, the interaction between the convection and the waves, and the triggering mechanism. The variation of the environment, for example, the jet and background baroclinicity, can impact the development of AEWs. In addition, the two-way interaction between the convection and the wave is thought to have an implication on the intensity and phase speed. Lastly, the extent to which the precursors of AEWs determine the nature of the wave will be explored. The results from this study are expected to improve our knowledge of AEW behaviors and can be extended to understand the intraseasonal and interannual variability of AEWs.