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Journal of Southern Hemisphere Earth Systems Science Journal of Southern Hemisphere Earth Systems Science SocietyJournal of Southern Hemisphere Earth Systems Science Society
A journal for meteorology, climate, oceanography, hydrology and space weather focused on the southern hemisphere
RESEARCH ARTICLE (Open Access)

The subtropical ridge in CMIP5 models, and implications for projections of rainfall in southeast Australia

Michael Grose, Bertrand Timbal, Louise Wilson, Janice Bathols and David Kent

Australian Meteorological and Oceanographic Journal 65(1) 90 - 106
Published: 2015

Abstract

The subtropical ridge (STR) is the mean pressure ridge in the mid-latitudes, and is one of the key features affecting climate variability and change in southeast Australia. Changes to the STR and associated changes to rainfall in a warming climate are of strong interest, and the new Coupled Model Inter-comparison Project phase 5 (CMIP5) model archive provides new opportunities to examine this. Here we show that the STR is projected to strengthen and move pole-ward under global warming, contributing to reduced rainfall in the cool season in southeast Australia. This result is largely consistent among 35 models examined, and CMIP5 shows a greater increase in intensity relative to position than CMIP3 did. We show that the simulation of the STR in the CMIP5 is similar to that of the previous CMIP3 in many respects, including the underestimation of both the historical trends in the STR intensity and the correlation between inter-annual STR intensity and southeast Australian rainfall. These issues mean we still have reduced confidence in regional rainfall projections for southeast Australia and suggest that CMIP5 rainfall projections for this region in April to October may be underestimates.

https://doi.org/10.1071/ES15007

© Commonwealth of Australia represented by the Bureau of Meterology 2015. This is an open access article distributed under the Creative Commons Attribution-NonCommerical-NoDerivatives 4.0 International License (CC BY-NC-ND).

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