Open AccessImpact of Regional Atmospheric Cloud Radiative Changes on Shifts of the Extratropical Jet Stream in Response to Global Warming
Author(s) -
Aiko Voigt,
Tiffany A. Shaw
Publication year - 2016
Publication title -
journal of climate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.315
H-Index - 287
eISSN - 1520-0442
pISSN - 0894-8755
DOI - 10.1175/jcli-d-16-0140.1
Subject(s) - extratropical cyclone , climate model , climatology , cloud forcing , cloud feedback , environmental science , atmospheric sciences , middle latitudes , radiative transfer , radiative forcing , jet stream , hadley cell , longwave , forcing (mathematics) , radiative cooling , cloud albedo , global warming , shortwave , climate change , jet (fluid) , cloud cover , climate sensitivity , cloud computing , geology , meteorology , general circulation model , physics , oceanography , quantum mechanics , computer science , thermodynamics , operating system
Climate models robustly project that global warming will lead to a poleward shift of the annual-mean zonal-mean extratropical jet streams. The magnitude of such shifts remains uncertain, however, and recent work has indicated a potentially important role of cloud radiative interactions. The model spread found in realistic simulations with interactive sea surface temperatures (SSTs) is captured in aquaplanet simulations with prescribed SSTs, because of which the latter setup is adapted here to study the impact of regional atmospheric cloud radiative changes on the jet position. Simulations with two CMIP5 models and prescribed regional cloud changes show that the rise of tropical high-level clouds and the upward and poleward movement of midlatitude high-level clouds lead to poleward jet shifts. High-latitude low-level cloud changes shift the jet poleward in one model but not in the other. The impact of clouds on the jet operates via the atmospheric radiative forcing that is created by the cloud changes and is qualitatively reproduced in a dry model, although the latter is too sensitive because of its simplified treatment of diabatic processes. The 10-model CMIP5 aquaplanet ensemble of global warming exhibits correlations between jet shifts, regional temperature changes, and regional cloud changes that are consistent with the prescribed cloud simulations. This provides evidence that the atmospheric radiative forcing from tropical and midlatitude high-level cloud changes contributes to model uncertainty in future jet shifts, in addition to the surface radiative forcing from extratropical cloud changes highlighted by previous studies.