Winds and precipitation are two meteorological variables of great impact on the economy and society, especially when extreme events occur. The objective of this study is to investigate the subtropical cyclone (SC) impacts on near‐surface wind extremes (defined by 95th percentile) and precipitation in the South Atlantic basin. For the period 1979–2015, the analysis used two reanalysis data (ERA5 and Climate Forecast System Reanalysis [CFSR]) and estimated precipitation from the Tropical Rainfall Measuring Mission (TRMM) considering the extended warm (from September to February) and cold (from March to August) seasons. A total of 169 SCs occurred in the warm season against 87 in the cold one. Two approaches are used to quantify SC impacts: Lagrangian, where the composites follow the cyclone center, and Eulerian, which considers the averaged environment during the cyclone lifecycle. In general, both approaches indicate SC contribution to the positive anomalies of mean and extreme near‐surface wind speeds to the east and northeast of a cyclogenetic region in southeastern Brazil (RG1). For all analyses conducted, wind speeds from CFSR are higher than in ERA5. The SC activity contributes to the enhancement of precipitation to the east and inside RG1 in an organized northwest‐southeast positive anomaly band from the continent to the ocean, while favoring drier conditions to the south. These positive precipitation anomalies are associated with an anomalous low pressure, low‐level moisture flux convergence and warm advection occurring at the same time with an upper‐level divergent flow near RG1. All these features are intensified in the cold season.

In the year 2023, the Earth experienced the highest near‐surface temperature anomalies ever recorded until then. In addition, several extreme weather and climate events occurred around the world, including in Brazil. In this context, the primary objective of this study is to analyze the anomalous temperature and precipitation patterns observed in Brazil during 2023, along with the most significant extreme events. Different datasets and methodologies were applied. The north coast of the state of São Paulo had the highest accumulation of rainfall recorded in Brazil in a single day. September, October, and November 2023 experienced the large precipitation deficits over the Amazon region, leading to a very intense and prolonged drought. The south of Brazil was affected by a large amount of precipitation in a short time, associated with cyclones, resulting in fatalities and economic losses. Southeast and Central‐West Brazil experienced two intense heatwaves in the austral spring, breaking daily temperature records in major cities like São Paulo and Rio de Janeiro. Overall, this study describes the main physical processes responsible for these extremes, along with the socioenvironmental impacts caused by most of them.

O Grupo de Estudos Climáticos da Universidade de São Paulo (GrEC-USP) foi criado em 1997 por alunos de graduação e pós-graduação de Ciências Atmosféricas com o intuito de realizar discussões mensais sobre o clima e sua variabilidade, com foco especial sobre o Brasil, colocando uma síntese dessas discussões em forma de relatórios mensais. Com passar dos anos o Grupo manteve suas discussões mensais e elaboração dos relatórios que passaram a ser disponibilizados a comunidade acadêmica e ao público em geral. Além dos relatórios, o grupo também passou a disponibilizar produtos para o monitoramento e previsão do clima, além de promover atividades de extensão e divulgação científica a serviço da sociedade. Este trabalho apresenta a evolução do Grupo ao longo dos anos, bem como toda sua produção científica, com o objetivo de divulgar suas atividades e homenagear todos os alunos e pesquisadores que participaram dos 25 anos de história GrEC-USP.

The Regional Climate Modeling system (RegCM) has undergone a significant evolution over the years, leading for example to the widely used versions RegCM4 and RegCM4-NH. In response to the demand for higher resolution, a new version of the system has been developed, RegCM5, incorporating the non-hydrostatic dynamical core of the MOLOCH weather prediction model. In this paper we assess the RegCM5’s performance for 5 CORDEX-CORE domains, including a pan-European domain at convection-permitting resolution. We find temperature biases generally in the range of -2 to 2 degrees Celsius, higher in the northernmost regions of North America and Asia during winter, linked to cloud water overestimation. Central Asia and the Tibetan Plateau show cold biases, possibly due to sparse station coverage. The model exhibits a prevailing cold bias in maximum temperature and warm bias in minimum temperature, associated with a systematic overestimation of lower-level cloud fraction, especially in winter. Taylor diagrams indicate a high spatial temperature pattern correlation with ERA5 and CRU data, except in South America and the Caribbean region. The precipitation evaluation shows an overestimation in South America, East Asia, and Africa. RegCM5 improves the daily precipitation distribution compared to RegCM4, particularly at high intensities. The analysis of wind fields confirms the model’s ability to simulate monsoon circulations. The assessment of tropical cyclone tracks highlights a strong sensitivity to the tracking algorithms, thus necessitating a careful model interpretation. Over the European region, the convection permitting simulations especially improve the diurnal cycle of precipitation and the hourly precipitation intensities.

Regional climate models (RCMs) from the CORDEX enable further investigations of the regional aspects of climate change impacts in South America. Here, we assess the CORDEX‐RCMs' present and future projections of extratropical cyclones, focusing on their frequency, early‐stage synoptic features, and added value relative to the global climate models (GCMs). Cyclones were tracked using a common algorithm in the present (1985–2005) and future RCP8.5 scenarios (2080–2099). ERA5 reanalysis was used as reference data in the present climate. Both GCMs and RCMs can identify the three major cyclone hot spots in South America: Argentina (ARG), La Plata Basin (LPB), and the south‐southeast Brazilian coast (SBR). RCMs improve GCMs' representation of the cyclogenesis frequency, adding value by decreasing the biases (~10%). Early‐stage cyclone synoptic structure also indicates RCMs' improvement of the low‐level fields by presenting mesoscale structures of warm/cold advection and moisture flux convergence/divergence in greater agreement with ERA5 (except for moisture flux divergence for LPB). RCMs and GCMs project a general decrease in cyclogenesis for the end of the century. For the cyclogenesis cores, GCMs' and RCMs' projections agree on the trend signals in SBR, LPB, and ARG in austral winter and disagree in ARG in austral summer. For LPB and SBR cyclogenesis, the RCMs and GCMs suggest a future increase in moisture flux convergence and warm advection at low levels, while a decrease in upper level divergence is projected. This indicates a reinforcement of cyclogenesis (negative sea‐level pressure trend) in the future due to the low‐level features and associated diabatic processes. For ARG, the future trends in the mean structure of cyclogenesis are relatively weak. Following other studies, cyclogenesis frequency may decrease; however, changes could occur in some important physical processes, such as low‐level moisture flux convergence and warm advection, suggesting more intense events in the future.