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Title: The Transient Circulation Response to Radiative Forcings and Sea Surface Warming

Tropospheric circulation shifts have strong potential to impact surface climate. But the magnitude of these shifts in a changing climate, and the attending regional hydrological changes, are difficult to project. Part of this difficulty arises from our lack of understanding of the physical mechanisms behind the circulation shifts themselves. In order to better delineate circulation shifts and their respective causes, we decompose the circulation response into (1) the "direct" response to radiative forcings themselves, and (2) the "indirect" response to changing sea surface temperatures. Using ensembles of 90-day climate model simulations with immediate switch-on forcings, including perturbed greenhouse gas concentrations, stratospheric ozone concentrations, and sea surface temperatures, we document the direct and indirect transient responses of the zonal mean general circulation, and investigate the roles of previously proposed mechanisms in shifting the midlatitude jet. We find that both the direct and indirect wind responses often begin in the lower stratosphere. Changes in midlatitude eddies are ubiquitous and synchronous with the midlatitude zonal wind response. Shifts in the critical latitude of wave absorption on either flank of the jet are not indicted as primary factors for the poleward shifting jet, although we see some evidence for increasing equatorward wave reflection overmore » the southern hemisphere in response to sea surface warming. Mechanisms for the northern hemisphere jet shift are less clear.« less
 [1] ;  [1] ;  [2]
  1. Univ. of Utah, Salt Lake City, UT (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0894-8755; KP1703010
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Climate; Journal Volume: 27; Journal Issue: 24
American Meteorological Society
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Org:
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES tropospheric circulation shifts; climate; hydrological changes