Lorenz Energy Cycle Climatology for the Southwestern Atlantic Cyclones

Danilo Couto de Souza , Pedro Leite da Silva Dias, Carolina Barnez Gramcianinov, Ricardo Camargo

This study presents a climatological assessment of the Lorenz Energy Cycle (LEC) applied to South Atlantic cyclones, using a Semi-Lagrangian framework. Over 6,700 cyclones were identified from ERA5 reanalysis (1979–2020), and LEC components were computed and averaged across four objectively defined life cycle phases: incipient, intensification, mature, and decay. Results reveal a coherent energy transfer structure: baroclinic conversions dominate during intensification, while barotropic conversions peak during the mature phase and reach magnitudes 2–3 times larger than baroclinic counterparts. Diabatic generation of eddy available potential energy plays a secondary but relevant role, particularly during intensification, occasionally surpassing baroclinic contributions. Eddy kinetic energy imports are most significant during the early phases, reinforcing development. Despite substantial variability among systems, an EOF analysis shows that most cyclones share a common energy structure, with variability manifesting as amplification or suppression of specific pathways. The leading EOFs are linked to differences in cyclone intensity, genesis region, and seasonality. Among the most intense systems, distinct clusters emerge with varying energetic configurations, some dominated by baroclinic processes, others by barotropic conversions or enhanced diabatic generation. These findings demonstrate that South Atlantic cyclones encompass a spectrum of dynamical behaviors and can be classified based on their energy cycle characteristics. This study provides the first large-sample application of the Semi-Lagrangian LEC to extratropical cyclones in the South Atlantic and highlights the importance of barotropic processes in their development. The results offer a robust framework for interpreting cyclone energetics and establish a comprehensive baseline for classifying these systems.