Model uncertainty in synoptic circulation patterns and precipitation changes in Southern South America using CMIP5 and CMIP6 models

OLMO, MATÍAS EZEQUIEL; BETTOLLI, MARÍA LAURA; BALMACEDA-HUARTE, ROCÍO

CLIMATIC CHANGE

SPRINGER

Año: 2023 vol. 176

0165-0009

The effects of global warming on the regional climate of southern South America (SSA)during the recent decades have been exhaustively documented with consistency throughoutthe literature. However, the projected changes on temperature- and precipitation-relatedclimate hazards depict an important uncertainty, mostly in the intensity of the changes.This work assessed a set of CMIP5 and CMIP6 global climate models (GCMs) in reproducingthe observed atmospheric circulation patterns (CPs) over SSA and their expectedchanges for the twenty-first century. Furthermore, the attribution of the seasonal precipitationchanges to changes in the CPs was explored for the late future (2070–2100). GCMswere generally able to represent the variety of CPs and their seasonal frequencies, althoughpresenting more deficiencies in capturing their respective precipitation patterns over SSA.Larger model agreement was found in the increasing and/or decreasing frequency of specificCPs for the near future (2040–2070) than for the late future, when model spreadbecame more noticeable. Particularly, CPs associated with larger positive rainfall anomaliesover southeastern South America—a hotspot for precipitation extremes—are expectedto become more frequent in the near future, whereas their changes in the longer term aremore uncertain. When performing an attributional study, precipitation changes showedimportant differences between GCMs and were often associated with changes in the intrapatternvariability rather than in the CP changing frequency. In this way, the modificationof the precipitation regime of SSA may not be explained only by changes in the large-scalecirculation but probably also by other regional-to-local features.