Westerly Biases Over the Equatorial Atlantic
Zermeño-Diaz, D.M. and Zhang, C. 2013. Possible root causes of surface westerly biases over the equatorial Atlantic in global climate models. Journal of Climate 26: 8154-8168.
As their contribution to the subject, Zermeño-Diaz and Zhang, as they describe it, "used a simple model for a well-mixed boundary layer over the tropical oceans and simulations from eight AGCMs to diagnose possible root causes of the surface westerly bias over the Atlantic during boreal spring," examining "the possible roles of the vertical structure of diabatic heating and zonal momentum entrainment across the top of the boundary layer."
When all was said and done, little was to be learned from their analysis, as the two researchers report their work merely lays the foundation for a mere hypothesis in diagnosing the cause of the bias. Neverthless, they add that "the implication of our results is that there might be no simple or single remedy for the westerly bias in GCMs." And they say that "this may be why this problem has been so stubborn and persistent up to the new generation of CMIP5 models." And, it might be added, why the problem still remains ... unresolved!