Potential vorticity diagnostics associated with the Tropical Easterly Jet over Africa and links to rainfall variability

This paper examines instabilities and wave activity associated with the Tropical Easterly Jet over West Africa, using potential vorticity (PV) concepts to contrast west and dry years in the region. Analyses of the meridional PV gradient indicate an abrupt shift in both location and magnitude of the instability associated with the TEJ during the transition from wet to dry years. PV perturbation analyses confirm that the upper-level development of waves differs considerably during wet and dry years. Further analysis shows that this is not a response to the changes in rainfall and associated latent heating. Numerical simulations provide further support for our results.