Feldstein, S. B., and W. R. Robinson, 1994: Comments on "Spatial structure of ultra-low frequency variability of the flow in a simple atmospheric circulation model" by I. N. James and P. M. James (October 1992, 118, 1211-1233). Quart. J. Roy. Met. Soc., 120, 739-745.
James and James (1992) examine internally generated interannual variability in a multi-layer primitive-equation model. The authors claim that the variability in the global mean relative angular velocity is associated with fluctuations in the mid-latitude zonally-averaged zonal winds. We question this relationship, and present results from an aqua-planet GCM which indicate that, instead, the global mean relative angular velocity is primarily related to changes in the tropical zonally-averaged zonal winds. Furthermore, we also question whether the 'ultra-low-frequency variability' examined by James and James is not simply just 'climate noise'.