GAFD Seminar: Sebastian Schemm (University of Cambridge)

In this talk, I will first discuss the apparent differences in the observed seasonal cycles of the storm tracks in the North Atlantic and North Pacific, as well as persistent biases in climate models' representation of the storm tracks in the Northern Hemisphere. Over the North Atlantic, monthly mean data suggest a maximum in baroclinic growth potential over the Gulf Stream, with a maximum in eddy kinetic energy occurring slightly downstream. In contrast, over the North Pacific, the maximum in baroclinic growth potential over the Kuroshio does not appear to cause a similar maximum in eddy kinetic energy. To explain this difference, I will introduce the concept of baroclinic conversion efficiency and demonstrate how monthly averages can obscure synoptic-scale dynamics and the seasonal cycle. Finally, with regard to modelled storm tracks, I will argue that the decade-long bias towards storm tracks that are too zonal, too weak, and too equatorward is largely due to a misrepresentation of moist diabatic processes on the synoptic scale.