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Abstract We extend the locking technique to separate the poleward shift of the atmospheric circulation in response to quadrupled CO2into contributions from (1) CO2increase, (2) cloud radiative effects, and (3) wind and surface humidity‐induced surface heat exchange. In aquaplanet simulations, wind and surface humidity‐induced surface heat exchange accounts for 30–60% of the Hadley cell edge and midlatitude eddy‐driven jet shift. The increase of surface specific humidity dominates and mostly follows global mean warming. Consistent with previous work the remaining shift is attributed to cloud radiative effects. Across CMIP5 models the intermodel variance in the austral winter circulation shift in response to quadrupled CO2is significantly correlated with the response of the subtropical‐subpolar difference of surface heat exchange. The results highlight the dominant role of surface heat exchange for future circulation changes.
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Disconnect Between Hadley Cell and Subtropical Jet Variability and Response to Increased CO 2
Abstract The subtropical jet (STJ) is thought to coexist with the edge of the Hadley cell (HC). However, recent studies reveal that the location of the STJ is poorly correlated with the latitude of the poleward edge of the HC. Here we use output from the Coupled Model Intercomparison Project Phase 5 to show that a weaker STJ is associated with a more poleward HC edge interannually, but there is a strengthening of the STJ and expansion of the HC in response to increased CO2. The HC expansion caused by increased CO2is much more rapid than the strengthening of the STJ. It is suggested that the differing response times and relationships between interannual variations and increased CO2are due to differing sensitivities of the HC and STJ to shifts in the eddy momentum fluxes.
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- Award ID(s):
- 1902409
- PAR ID:
- 10453978
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 46
- Issue:
- 12
- ISSN:
- 0094-8276
- Page Range / eLocation ID:
- p. 7045-7053
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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