Variations in ozone and greenhouse gases as drivers of Southern Hemisphere climate in a medium-complexity global climate model
The climate of the Southern Hemisphere (SH) is being affected not only by the global increase in the concentration of greenhouse gases (GHG) but also by the ongoing recovery of stratospheric ozone. The competing roles of both are usually studied by means of state-of-the-art global climate models (GCM) due to the complexity in the atmospheric processes and interactions involved. The main objective of this paper is to determine whether quantitatively similar results can be achieved using a simpler, medium-complexity GCM. This includes addressing the sensitivity of the medium-complexity model to changes in GHG and ozone concentrations as well as looking into the plausible mechanisms driving such patterns of variations in atmospheric circulation, precipitation and temperature extremes. Two sets of simulations are performed: one with fixed sea surface temperatures (SST) and another one making use of a mixed-layer ocean model coupled to the GCM. Results show that the GCM is highly sensitive to changes in the atmospheric composition, and that the largest differences are found when SST are allowed to vary accordingly, particularly in the case of temperature extremes. Specific analyses are also performed on changes in subtropical precipitation over the continental regions of the SH, with moisture budget decomposition being applied in order to provide explanations for the rainfall changes described in the manuscript.
KeywordsOzone and greenhouse gases Southern Hemisphere Moisture budget SPEEDY Global climate models
The authors would like to thank the two anonymous reviewers for their constructive comments that led to a substantial improvement of the paper. The first author acknowledges the support from the Abdus Salam International Centre for Theoretical Physics in the form of a Junior Associate position during which most of this research was done. Research leading to this manuscript has also been supported by Grant PICT 2016-1898 to the University of Buenos Aires.
- Wilks DS (2006) Statistical methods in the atmospheric sciences, 2nd. End. Academic Press, Waltham, p 141Google Scholar