Plausible drying and wetting scenarios for summer rainfall in South-eastern South America: A storyline approach

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Abstract

Summer rainfall trends in South-eastern South America (SES) affect an area where around 200 million people live. Literature identifies more than one driving mechanism for them, some of which have opposing effects. However, it is still not clear how much each mechanism has contributed to the observed trends or how their combined influence will affect future trends. In this work, we study how SES summer rainfall long-term changes in CMIP6 simulations can be explained by mechanisms related to large-scale extratropical circulation responses in the Southern Hemisphere (SH) to remote drivers such as warming sea surface temperature patterns or the delay of the stratospheric polar vortex breakdown date. While the change projected by the multimodel ensemble mean is a wetting, when considering all plausible large-scale storylines, drying scenarios are also found. In addition, we show how the definition of the SES regional box can impact the results, given that if the spatial pattern characterizing the dynamical influences are complex and the impacts can be averaged out if large-scale influences are not considered when aggregating.

Bio

Julia Mindlin is a PhD candidate from the University of Buenos Aires. Her research interests are the uncertainty atmospheric circulation under changing climates, El Niño Southern Oscillation variability and change, and regional climate change. She’s currently visiting the University of Reading, UK.

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