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Seasonally and Regionally Dependent Shifts of the Atmospheric Westerly Jets under Global Warming

Journal Article · · Journal of Climate
 [1];  [1];  [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
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A distinct feature of the atmospheric circulation response to increasing greenhouse gas forcing is the poleward shift of the zonal-mean westerly jet. The dynamical mechanisms of the zonal-mean poleward jet shift have been extensively studied in literature. At seasonal/regional scales, however, the westerly jets can shift equatorward, such as in the early-summer Asia–Pacific region, the late-winter America–Atlantic region, and the winter/spring east Pacific. These equatorward jet shifts imply climate impacts distinct from those of the poleward shifts, yet their causes are not well understood. In this work, based on a hierarchy of coupled, prescribed-SST, and aquaplanet simulations, we attribute the seasonal/regional equatorward jet shifts to the enhanced tropical upper-level warming (ETUW), which arises from both the tropical moist adiabat and the enhanced equatorial surface warming. By steepening the meridional temperature gradient in the subtropical upper-to-middle level and assisted by positive eddy feedback, the ETUW increases the zonal wind equatorward of the climatological jet. When the regional/seasonal meridional temperature gradients (or equivalently the westerly jets) are weak and peak close to the tropics, the ETUW effect overcomes the poleward jet-shift mechanisms and leads to the equatorward jet shifts. This climatological-state dependency is consistently seen in the decomposed jet responses to uniform warming and surface warming pattern, and further demonstrated through idealized aquaplanet experiments with designed climatological states. For uniform warming, the ETUW arising from moist adiabat makes the general poleward jet shifts insignificant in the aforementioned favorable regions/seasons. For warming pattern, the ETUW from enhanced equatorial warming drives substantial equatorward jet shifts in these favorable seasons/regions.
Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
AC02-05CH11231; AC05-76RL01830
OSTI ID:
1889466
Report Number(s):
PNNL-SA-172800
Journal Information:
Journal of Climate, Journal Name: Journal of Climate Journal Issue: 16 Vol. 35; ISSN 0894-8755
Publisher:
American Meteorological SocietyCopyright Statement
Country of Publication:
United States
Language:
English

References (36)

What can moist thermodynamics tell us about circulation shifts in response to uniform warming?: MOIST THERMODYNAMICS AND CIRCULATION journal May 2016
The ERA5 global reanalysis journal June 2020
Using aquaplanets to understand the robust responses of comprehensive climate models to forcing journal May 2014
Northern Hemisphere Stationary Waves in a Changing Climate journal November 2019
Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century journal January 2003
A consistent poleward shift of the storm tracks in simulations of 21st century climate: POLEWARD SHIFT OF THE STORM TRACKS journal September 2005
Simulated changes in the extratropical Southern Hemisphere winds and currents journal January 2006
Intensification of the Pre‐Meiyu Rainband in the Late 21st Century journal July 2019
The Community Earth System Model Version 2 (CESM2) journal February 2020
Southward Shift of Westerlies Intensifies the East Asian Early Summer Rainband Following El Niño journal September 2020
Causes of change in Northern Hemisphere winter meridional winds and regional hydroclimate journal September 2015
Enhanced equatorial warming causes deep-tropical contraction and subtropical monsoon shift journal October 2019
Amplified Madden–Julian oscillation impacts in the Pacific–North America region journal June 2020
Decadal predictability of late winter precipitation in western Europe through an ocean–jet stream connection journal July 2019
Southern Hemisphere Atmospheric Circulation Response to Global Warming journal May 2001
Phase Speed Spectra of Transient Eddy Fluxes and Critical Layer Absorption journal March 1991
Response of the Zonal Mean Atmospheric Circulation to El Niño versus Global Warming journal November 2008
Phase Speed Spectra and the Latitude of Surface Westerlies: Interannual Variability and Global Warming Trend journal November 2008
The Position of the Midlatitude Storm Track and Eddy-Driven Westerlies in Aquaplanet AGCMs journal December 2010
The Steady-State Atmospheric Circulation Response to Climate Change–like Thermal Forcings in a Simple General Circulation Model journal July 2010
Can the Increase in the Eddy Length Scale under Global Warming Cause the Poleward Shift of the Jet Streams? journal July 2011
Delineating the Eddy–Zonal Flow Interaction in the Atmospheric Circulation Response to Climate Forcing: Uniform SST Warming in an Idealized Aquaplanet Model journal July 2013
Sensitivities and Mechanisms of the Zonal Mean Atmospheric Circulation Response to Tropical Warming journal August 2013
A Diagnosis of the Seasonally and Longitudinally Varying Midlatitude Circulation Response to Global Warming* journal July 2014
Local Finite-Amplitude Wave Activity as a Diagnostic of Anomalous Weather Events journal January 2016
Sensitivity of the Latitude of the Surface Westerlies to Surface Friction journal August 2007
Atmospheric Circulation Response to an Instantaneous Doubling of Carbon Dioxide. Part II: Atmospheric Transient Adjustment and Its Dynamics journal February 2013
California Winter Precipitation Change under Global Warming in the Coupled Model Intercomparison Project Phase 5 Ensemble journal September 2013
Response of the Midlatitude Jets, and of Their Variability, to Increased Greenhouse Gases in the CMIP5 Models journal September 2013
The Role of Subtropical Irreversible PV Mixing in the Zonal Mean Circulation Response to Global Warming–Like Thermal Forcing journal March 2014
Impact of Regional Atmospheric Cloud Radiative Changes on Shifts of the Extratropical Jet Stream in Response to Global Warming journal December 2016
Origins of East Asian Summer Monsoon Seasonality journal September 2020
Mechanisms of ENSO-forcing of hemispherically symmetric precipitation variability journal April 2005
Space-Time Spectral Analysis and its Applications to Atmospheric Waves [時空間スペクトル解析法と大気波動への応用] journal January 1982
The Cloud Feedback Model Intercomparison Project (CFMIP) contribution to CMIP6 journal January 2017
Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization journal January 2016

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Related Subjects

54 ENVIRONMENTAL SCIENCES
Atmospheric circulation
Climate change
Jets