Wavier jet streams driven by zonally asymmetric surface thermal forcing

• DOI: 10.1073/pnas.2200890119
• Publication Date: 2022-09-12T19:19:20Z
• Authors: Woosok Moon; Baek-Min Kim; Gun-Hwan Yang; John S. Wettlaufer
• Keywords: Jet stream; Middle latitudes; Eddy; Forcing (mathematics)

Recent studies have argued that global warming is responsible for a wavier jet stream, thereby driving midlatitude extreme flooding and drought. Polar amplification—the relative enhancement of high-latitude temperatures under warming—is to be the principal climate state extremes. Namely, decreased meridional temperature gradient suppresses mean zonal winds, leading jets. However, although observations are consistent with such linkage, detailed dynamical mechanism still debated. Here, we argue Northern Hemisphere land–sea thermal forcing contrast underlies zonally asymmetric drives response in planetary geostrophic motion, which provides balanced fields synoptic eddies midlatitudes thus streams. We show when barotropic wind U smaller than threshold, proportional β -plane effect dry static stability, flow field exhibits dramatic transition from confined near surface one reaching upper atmosphere. As enhances polar amplification, stream intensity suppressed. The confluence these effects leads