Evaluation of the ability of CMIP6 models to simulate precipitation over Southwestern South America: Climatic features and long-term trends (1901?2014)

Abstract

This study evaluates the performance of precipitation simulated in the historical runs of the Climate Model Intercomparison Project Phase 6 (CMPI6) in capturing the complex spatial and temporal patterns observed over Southwestern South America (SWSA). Precipitation outputs from 14 general circulation models (GCMs) were compared with observations from CRU TS 4.03 database for the period 1901–2014, using a set of statistical metrics, with particular focus in the quantification of the long-term precipitation decline that triggered recent recurrent drought conditions over SWSA. The main features of regional precipitation were adequately captured by the majority of CMIP6 models, although with a wet bias south of 35°S especially along the Andes ranges and in southern Chile, which can exceed 100 mm during the winter rainy season. The magnitude of the long-term precipitation decline was reasonably captured by the different GCMs, but model outputs tend to locate the maximum in precipitation decrease south of the position of the observed trends. The precipitation decline can be linked to the observed positive long-term trend in SLP over the subtropical southeast Pacific Ocean. Nevertheless, only few GCMs were able reproduce the spatial patterns of observed SLP trends. Finally, considering a comprehensive rating index, we selected a subset of five GCMs that best reproduced the climatological features of precipitation and its temporal and spatial changes over the study area, with a brief discussion of implications for the assessment of future precipitation over SWSA.