Janni Yuval,
EAPS Distinguished Postdoctoral Fellow, MIT
Title "Eddy activity response to projected temperature changes and the Pacific seasonal cycle"
Abstract: Baroclinic eddies are responsible for transporting heat and moisture from midlatitudes poleward, and play a crucial role in setting Earth’s climate. It is thus important to elucidate the baroclinic eddies response to both natural and anthropogenic forcings. In this talk, I will discuss the effects of the projected temperature changes as well as the effects of the Pacific seasonal cycle on midlatitudes eddies.
First, global warning projections show anomalous warming at the Arctic surface and in the upper tropical troposphere. Using a modified Newtonian cooling scheme, we investigate the relative importance of these changes on eddy activity in the Northern hemisphere. We find that eddy kinetic energy changes are dominated by the tropical upper level warming, which tends to weaken eddy kinetic energy due to increased static stability. On the other hand, eddy heat flux changes are dominated by the Arctic amplification, which tends to reduce the temperature gradient and weaken eddy heat flux at the lower levels. Second, in the seasonal cycle, we find a strong relation between the jet type (eddy-driven vs subtropical) and the strength of the eddies. We propose that such transition between a subtropical to eddy driven jet during different seasons in the Pacific is related to the existence of the Pacific midwinter minimum in eddy activity.
