Investigating the past and future trends of cyclone formations/transitions over the South Atlantic Ocean basin

Abstract

Synoptic scale cyclones have a great influence on weather and climate conditions in South America and in the South Atlantic Ocean basin. In particular, these cyclones are associated with strong winds and waves over the sea. Recent knowledge indicates that these systems can acquire distinct characteristics (tropical, subtropical and extratropical) and experiment transitions throughout their life cycle. It was exactly this new view that led scientists to classify Catarina as the first hurricane in the South Atlantic basin, breaking a scientific paradigm until then that climatological conditions did not allow such systems in the region. After that, the number of studies investigating the occurrence of different phases of cyclones has grown, and in February 2019 a purely tropical formation was documented (tropical cyclone Iba). One of the questions that arises is whether other tropical events occurred before Catarina or whether its formation could be explained by changes in climate. The need to understand past climate to explain future trends has driven both the development of centenary reanalyses and the improvement of coupled numerical models at high spatial resolution. In this context, our main objective is to investigate long-term climate trends of the different cyclone phases (tropical, extratropical and subtropical) and associated extreme events (wind and rain) in the South Atlantic basin. For this, 20th century reanalysis (1900-2010) and high spatial resolution global climate projections from the CMIP6-HighResMIP project will be used. The 20th century reanalysis will allow us to answer whether changes are taking place in the characteristics of synoptic scale cyclones, while climate projections will indicate future trends in their characteristics. (AU)