Impact of stratospheric ozone on Southern Hemisphere circulation change: A multimodel assessment

Abstract

[1] The impact of stratospheric ozone on the tropospheric general circulation of the Southern Hemisphere (SH) is examined with a set of chemistry-climate models participating in the Stratospheric Processes and their Role in Climate (SPARC)/Chemistry-Climate Model Validation project phase 2 (CCMVal-2). Model integrations of both the past and future climates reveal the crucial role of stratospheric ozone in driving SH circulation change: stronger ozone depletion in late spring generally leads to greater poleward displacement and intensification of the tropospheric midlatitude jet, and greater expansion of the SH Hadley cell in the summer. These circulation changes are systematic as poleward displacement of the jet is typically accompanied by intensification of the jet and expansion of the Hadley cell. Overall results are compared with coupled models participating in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), and possible mechanisms are discussed. While the tropospheric circulation response appears quasi-linearly related to stratospheric ozone changes, the quantitative response to a given forcing varies considerably from one model to another. This scatter partly results from differences in model climatology. It is shown that poleward intensification of the westerly jet is generally stronger in models whose climatological jet is biased toward lower latitudes. This result is discussed in the context of quasi-geostrophic zonal mean dynamics.

Aerosol and ozone changes as forcing for climate evolution between 1850 and 2100

“…All theses features in the model-calculated column ozone climatology are in line with the trends reported from observations (WMO 2011;SPARC 2010). In view of the well-established impact of the so-called ozone hole on the Antarctic climate (Son et al 2010), it is important that the After 2006, the ozone trajectories of the different scenarios start to diverge. The ODS evolution being the same in all the scenarios, the divergence is due to the differences in the specified GHG evolution.…”

The Antarctic ozone hole during 2010

“…In the climate modelling arena, recent studies have continued to demonstrate the important role that stratospheric ozone depletion has played in influencing the climate of the southern hemisphere and the Antarctic region, particularly in the austral summer (e.g. Perlwitz et al 2008;Gillett et al 2009;Waugh et al 2009a,b;Karpechko et al 2010;McLandress et al 2010;Son et al 2010;SPARC CCMVal 2010;Arblaster et al 2011;Deushi and Shibata 2011;Hu et al 2011;Forster et al 2011;Kang et al 2011;McLandress et al 2011;Ndarana et al 2011;Polvani et al 2011a,b;Sigmond et al 2011). A particular emphasis of work in the modelling community continues to be the accurate simulation of stratospheric thermodynamics, particularly in relation to minimising biases in Antarctic winter temperatures, and adequately treating feedbacks from dynamical processes associated with wave-induced momentum transfer and mixing (SPARC CCMVal 2010;WMO 2011a).…”

Numerical Modeling of Climate-Chemistry Connections: Recent Developments and Future Challenges

“…Simulations performed with CCMs support these findings (Chapter 3 in [3]); most CCMs are able to reproduce adequately the variations and long-term evolution of stratospheric temperature over the last five decades (Figure 2). Results derived from CMIP3 climate model simulations (Figure 3) in general show less agreement with the radiosonde climatology; but nevertheless it is demonstrated that the observed global mean cooling trend in the lower stratosphere is clearly underestimated by AOGCMs that do not include the decline of stratospheric ozone concentration over the last three decades [42,43]. This strongly indicates the significant role of stratospheric ozone in connection with climate (see Section 3.2.2).…”