African Easterly Wave Tracks as Simulated by CMIP5 Models

African Easterly Waves (AEWs) impact Sahel rainfall and serve as a trigger disturbance for tropical cyclones (TCs) in the North Atlantic Ocean. Currently, there is no agreement regarding the projected TC trends for the future. So far, there has been very little investigation into the changes in intensity and location of AEWs from year to year and how these changes would impact the TC activity of the Atlantic Basin and rainfall across the Sahel. Gaining a more detailed understanding of AEW behavior within global climate models will reduce the uncertainty surrounding these TC precursors, potentially yielding higher confidence in future Sahel rainfall and TC trends.

This study will use two tracking methods; an objective method as well as an automatic method, to identify and track AEWs at multiple levels. The magnitude, frequency, location, and speed of the AEWs will be compared between reanalysis products (e.g. JRA-55, CFSR, ERA-Interim) and the coupled historical simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). This will provide insight into the ability of global climate models to represent tracks of AEWs and the relationship with the simulated environment in the CMIP5 models. After establishing historical biases, the tracking techniques will be applied to future simulations within the CMIP5 experiments. Identifying the extent to which AEW track characteristics are changing will provide a better understanding of the future projections for Sahel rainfall and Atlantic TCs.