ClimaTea: "The abrupt seasonal transition of the Northern Hemisphere general circulation: mechanisms and future changes"

Speaker: Tiffany Shaw (Columbia)

Abstract:"The Northern Hemisphere exhibits an abrupt regime transition between winter in summer involving the organization of the flow into subtropical anticyclones and monsoons. The transition provides a useful example of how moisture and momentum transports by planetary-scale waves are coordinated to dominate the large-scale circulation. The mechanisms of the abrupt transition are explored in idealized aquaplanet model simulations with a prescribed subtropical zonally asymmetric SST perturbation. The results are understood using quasi-geostrophic dynamics and provide new indicators for assessing the transition in the real atmosphere. They can also be used to understand why the transition in the Southern Hemisphere is less abrupt. Future changes in the circulation transition will be discussed in the context of the CMIP5 simulations"