The impact of SST biases in the tropical east pacific and agulhas current region on atmospheric stationary waves in the southern hemisphere

Chaim I. Garfinkel*, Ian White, Edwin P. Gerber, Martin Jucker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Climate models in phase 5 of the Coupled Model Intercomparison Project (CMIP5) vary significantly in their ability to simulate the phase and amplitude of atmospheric stationary waves in the midlatitude Southern Hemisphere. These models also suffer from a double intertropical convergence zone (ITCZ), with excessive precipitation in the tropical eastern South Pacific, and many also suffer from a biased simulation of the dynamics of the Agulhas Current around the tip of South Africa. The intermodel spread in the strength and phasing of SH midlatitude stationary waves in the CMIP archive is shown to be significantly correlated with the double-ITCZ bias and biases in the Agulhas Return Current. An idealized general circulation model (GCM) is used to demonstrate the causality of these links by prescribing an oceanic heat flux out of the tropical east Pacific and near the Agulhas Current. A warm bias in tropical east Pacific SSTs associated with an erroneous double ITCZ leads to a biased representation of midlatitude stationary waves in the austral hemisphere, capturing the response evident in CMIP models. Similarly, an overly diffuse sea surface temperature gradient associated with a weak Agulhas Return Current leads to an equatorward shift of the Southern Hemisphere jet by more than 38 and weak stationary wave activity in the austral hemisphere. Hence, rectification of the double-ITCZ bias and a better representation of the Agulhas Current should be expected to lead to an improved model representation of the austral hemisphere.

Original languageAmerican English
Pages (from-to)9351-9374
Number of pages24
JournalJournal of Climate
Issue number21
StatePublished - 1 Nov 2020

Bibliographical note

Funding Information:
Acknowledgments. CIG, IW, and ME acknowledge the support of a European Research Council starting grant under the European Union Horizon 2020 Research and Innovation Programme (Grant Agreement 677756). EPG acknowledges support from the U.S. NSF through Grant AGS-1852727. MJ acknowledges support from the Australian Research Council (ARC) Centre of Excellence for Climate Extremes (CE170100023) and ARC Grant FL 150100035. We thank Ori Adam and three reviewers for helpful comments on an earlier version of this manuscript. Code for this model configuration will be made available on GitHub as part of the MiMA v2.0 release.

Publisher Copyright:
© 2020 American Meteorological Society.


  • Boundary currents
  • Intertropical convergence zone
  • Stationary waves


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