Stratosphere-resolving CMIP5 models simulate different changes in the Southern Hemisphere
- 236 Downloads
This work documents long-term changes in the Southern Hemisphere circulation in the austral spring–summer season in the Coupled Intercomparison Project Phase 5 models, showing that those changes are larger in magnitude and closer to ERA-Interim and other reanalyses if models include a dynamical representation of the stratosphere. Specifically, models with a high-top and included dynamical and—in some cases—chemical feedbacks within the stratosphere better simulate the lower stratospheric cooling observed over 1979–2001 and strongly driven by ozone depletion, when compared to the other models. This occurs because high-top models can fully capture the stratospheric large scale circulation response to the ozone-induced cooling. Interestingly, this difference is also found at the surface for the Southern Annular Mode (SAM) changes, even though all model categories tend to underestimate SAM trends over those decades. In this analysis, models including a proper dynamical stratosphere are more sensitive to lower stratospheric cooling in their tropospheric circulation response. After a brief discussion of two RCP scenarios, our study confirms that at least for large changes in the extratropical regions, stratospheric changes induced by external forcing have to be properly simulated, as they are important drivers of tropospheric climate variations.
KeywordsStratosphere Southern Hemisphere change CMIP5 models
We acknowledge the World Climate Research Program (WCRP) Working Group on Climate Modeling, responsible for the CMIP5 activity. Gloria Rea is supported by StratoCLIM Framework Programme (FP7) Collaborative Project, Atmospheric Processes, Eco-Systems and Climate Change, ENV.2013.6.1-2, Grant Agreement no. 603557. Thank you to all modeling groups for producing and making available the simulations.
- Bracegirdle TJ, Shuckburgh E, Sallee JB, Wang Z, Meijers A, Bruneau N, Phillips T, Wilcox LJ (2013) Assessment of surface winds over the Atlantic, Indian, and Pacific Ocean sectors of the Southern Ocean in CMIP5 models: historical bias, forcing response, and state dependence. Geophys Res Atmos 118:547–562. doi: 10.1002/jgrd.50153 CrossRefGoogle Scholar
- Limpasuvan V, Hartmann DL (2000) Wave-maintained annular modes of climate variability. J Clim 13:4414–4429. doi: 10.1175/1520-0442(2000) 013<4414%3AWMAMOC>2.0.CO%3B2 CrossRefGoogle Scholar
- Manzini E, Steil B, Bruhl C, Giorgetta MA, Kruger K (2003) A new interactive chemistry-climate model: 2. Sensitivity of the middle atmosphere to ozone depletion and increase in greenhouse gases and implications for recent stratospheric cooling. J Geophys Res 108:ACL10–ACL11. doi: 10.1029/2002JD002977 CrossRefGoogle Scholar
- Waugh D et al (2013) Recent changes in the ventilation of the southern oceans. Science 568Google Scholar