Evaluation of CMIP5 and CMIP6 models based on weather types applied to the south Atlantic ocean

Abstract

Changes in climate in the South Atlantic region and adjacent regions have been described in numerous works using projections from global climate models from CMIP5 and CMIP6. This paper presents an evaluation of the ability of these models to reproduce the atmospheric circulation patterns (weather types) and their seasonal and inter-annual variability. The analyses are performed based on the probability of occurrence of weather types in the historical period and in future projections. The scatter index and the relative entropy are the statistical parameters used to evaluate the models' performance in the historical period. Future projections consist of RCP2.6, 4.5 and 8.5 scenarios for the CMIP5 models and the SSP126, 245, 370 and 585 scenarios for the CMIP6 and are assessed at different time intervals: short term (2015-2039), mid-term (2040-2069) and long term (2070-2100). The performance of projections is measured by analysing their consistency, that is, based on the similarity between projections of the same scenario in different models. The results show that the reproduction of the probability of occurrence of historical weather types and their seasonal and interannual variability was better performed by ACCESS1-0, HadGEM2-ES, HadGEM2-CC, CMCC-CM and MPI-ESM-P when assessing the models from CMIP5, and by HadGEM3-GC31-MM, ACCESS-ESM1-5, ACCESS- CM2 and MRI-ESM-P when assessing the models from CMIP6. As for future projections, only the BESM-AO2-5, GFDL-ESM4 and HadGEM3-GC31-MM models showed inconsistency in one or more scenarios.