This work documents the main features of six subtropical cyclones occurred between the years 2010 and 2016 over the southwestern South Atlantic Ocean, near the Brazilian coast, which received names (with the exception of one) from the Brazilian Navy Hydrographic Center. The fine-resolution ERA5 reanalysis and rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) were used to describe the synoptic environment and the adverse weather conditions during the six events. The support of a small-amplitude trough at mid-levels or a cut-off low, weak vertical wind shear, and moisture flux convergence are the main features contributing to the subtropical cyclogenesis at the surface. On the other hand, sea surface temperature (SST) presents a secondary contribution since the cyclones develop over the ocean with a wide range of SST values (from 22.5 °C to 28.6 °C in the initial phase of cyclones). The six subtropical cyclones are less deep in the atmosphere column than the tropical ones and, unlike the extratropical cyclones, they have little or no westward tilt with an increase in height. The studied subtropical cyclones produced adverse weather conditions such as (a) strong winds (reaching 17 m·s−1 at 10 m high) for a long period occurring east/southeastward of the cyclone center, and (b) high amounts of rainfall along the southeastern coast of Brazil, where the accumulated rainfall varied between 170 to 350 mm, being in most cases higher than the monthly climatology. Over the continent, the Brazilian states of Rio de Janeiro and Espírito Santo were the most affected by the intense rainfall associated with the cyclones.

A região sudeste do Brasilapresentou déficit de precipitação no mês de janeiro dos anos de 2014 e 2015, o que impactoua disponibilidade de água para o consumo humano, a agricultura e a produção de energia hidrelétrica. O volume dos reservatórios de água passou a alcançar seus níveis mais baixos.Nesse contexto o objetivo do presente estudoé verificar se o padrão de anomalias atmosféricas associados à seca em janeiro de 2014 foi similar ao ocorrido com a seca de janeiro de 2015.  Entre os resultados têm-se que em ambos os anos há o deslocamento do Anticiclone Subtropical do Atlântico Sul (ASAS) para oeste de sua posição climatológica, implicando em anomalias positivas de pressão atmosférica sobre o sudeste do Brasil e anomaliaspositivas de temperatura da superfície do mar próximas à costa sul-sudeste do país. Essas características atmosféricas desfavorecem a ocorrência de precipitação no sudeste do Brasil. Palavras-chave: Sudeste do Brasil, verões anômalos, déficit de precipitação.

On 6 March 2010, Anita, the first subtropical cyclone observed over the South Atlantic Ocean, formed near the southeastern coast of Brazil, and during its life cycle, Anita almost acquired a tropical structure. The potential of Anita to undergo tropical transition in scenarios of increased sea surface temperature (SST) was investigated through a set of numerical sensitivity experiments. The results show that, if the SST had been 2°C warmer throughout Anita's life cycle, the system would have undergone tropical transition in its maturity stage; however, if the SST had increased only during Anita's quasi‐stationary period, the tropical transition completion would have occurred only with higher values of SST (6°C).

A região sul do estado de Minas Gerais (RSMG) possui topografia acidentada tendo como destaque a Serra da Mantiqueira. Devido a essa característica peculiar, em geral, os modelos climáticos com resoluções horizontais grosseiras não conseguem representar adequadamente o clima da região. A fim de identificar o impacto da topografia da RSMG na temperatura do ar, precipitação e circulação atmosférica, foram realizados dois experimentos numéricos, em alta resolução (12 km), com o Regional Climate Modelversion 4 (RegCM4): um denominado de controle (CTRL) e outro em que a topografia foi removida (STOPO). O período das simulações foi de novembro de 2008 a fevereiro de 2009. A temperatura do ar simulada no experimento CTRL foi validada através de comparação com a Climate Forecast System Reanalysis (CFSR), enquanto que a precipitação com as estimativas do Tropical Rainfall Measuring Mission (TRMM). Ambas as variáveis simuladas também foram comparadas com dados medidos em estações meteorológicas convencionais do Instituto Nacional de Meteorologia (INMET). Entre os resultados têm-se que a ausência da topografia conduz a maiores temperaturas médias mensais e acumulados de precipitação, bem como a desconfiguração da circulação de brisa de vale e montanha sobre a RSMG. Palavras-chave: Sul de Minas Gerais. Topografia. Modelo Climático. Topography influence of the Southern Region of Minas Gerais State on the atmospheric variables simulated by RegCM4 A B S T R A C T The Southern Region of the Minas Gerais State (RSMG) has rugged topography, such as the Serra da Mantiqueira. Due to this peculiar feature, in general, climate models with coarse horizontal resolutions may not represent adequately the climate of this region. To identify impacts of RSMG topography on air temperature, precipitation and atmospheric circulation, two high resolution (12 km) numerical experiments were performed using the Regional Climate Modelversion 4 (RegCM4): a control simulation (CTRL) and a second one with removed topography (STOPO). The simulation period was from November 2008 to February 2009. Simulated air temperature fields from CTRL were validated against Climate Forecast System Reanalysis (CFSR), and rainfall against Tropical Rainfall Measuring Mission (TRMM) ground estimates. Simulated variables were also compared with data from conventional meteorological stations of the National Institute of Meteorology (INMET). Among the results we highlight that average monthly temperatures and precipitation increase, and the circulations of valley and mountain breeze are obliterated with suppressed topography.

A precipitação é uma variável de grande importância para a compreensão do clima em diferentes escalas espaciais como, por exemplo, a regional e global. Se os modelos climáticos conseguem reproduzir a variabilidade espacial e temporal da precipitação, se tem confiabilidade para o uso deles em estudos do clima futuro. Portanto, este estudo tem como objetivo avaliar a performance de 50 modelos climáticos globais do Coupled Model Intercomparison Project Phase 6 (CMIP6) a fim de selecionar aqueles que melhor simulam a climatologia da precipitação sobre dois subdomínios da América do Sul (sul da Amazônia – AMZ e sudeste do Brasil – SDE), no período histórico (1995-2014). Para isso, são realizadas análises estatísticas entre cada modelo e dados considerados como referência (Global Precipitation Climatology Project Version 1.2 - GPCP e Climate Prediction Center Merged Analysis of Precipitation - CMAP). Os resultados indicam que o modelo INM-CM5-0 é o que melhor simula a precipitação na AMZ e os modelos MPI-ESM1-2-HR e NESM3 na região SDE. Como estudos com modelos globais necessitam de muitos recursos computacionais, é mais conveniente selecionar aqueles que mostram boa performance para ambas as regiões, assim, são indicados os modelos EC-Earth3-Veg-LR, INM-CM4-8, INM-CM5-0 e MPI-ESM1-2-HR.Palavras-chave: Modelos de Circulação Geral, CMIP, IPCC, América do Sul.Performance of CMIP6 climate models in simulating precipitation in subdomains of South America in the historical period  A B S T R A C TPrecipitation is a variable of great importance in understanding the climate at different spatial scales, such as regional and global. Whether climate models can reproduce the spatial and temporal variability of precipitation, they are reliable for their use in future climate studies. Therefore, this study aims to evaluate the performance of 50 global climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) in order to select those that best simulate the climatology of precipitation over two subdomains of South America in the historical period (1995- 2014): southern Amazon (AMZ) and southeastern Brazil (SDE). In this sense, statistical analyses are performed between each model and data considered as reference (Global Precipitation Climatology Project Version 1.2, GPCP and Climate Prediction Center Merged Analysis of Precipitation - CMAP). The results indicate that the INM-CM5-0 model is the one with best performance in simulating precipitation in AMZ and MPI-ESM1-2-HR and NESM3 models in SDE. As studies with global models need a lot of computational resources, it is more convenient to select those models with good performance in both regions. In this way, EC-Earth3-Veg-LR, INM-CM4-8, INM-CM5-0 and MPI-ESM1-2-HR are the models indicated for both regions.Keywords: General Circulation Models, CMIP, IPCC South America

The Paraiba do Sul River Basin (PSRB) is a vital source of water resources in Brazil, providing water for human consumption, industry, agriculture, and hydroelectric energy generation. As part of one of the most developed areas of the country, in the Southeast of Brazil, the region is vulnerable to the impacts of climate change, with evidence of extreme events such as droughts and floods affecting the availability and quality of water. Hence, this study analyzes precipitation and streamflow rates data from the PSRB between 1939–2020 to investigate the spatial variability of average patterns and extreme events, trends, and their relationship with urban growth and socioeconomic development. The analysis reveals significant spatial variations in precipitation and runoff rates, with higher altitude areas, such as the Serra da Mantiqueira, exhibiting higher average values. Moreover, the Mann–Kendall trend results showed in most of the sites no significant trend regarding precipitation data; however, about 50% of the sites in the PSRB presented a decreasing trend of runoff rates. Since the precipitation does not explain identified changes in the hydrological patterns, the evaluation of the area’s urban growth and socioeconomic development throughout the decades suggested that human activities, such as those associated with urbanization, have played a significant role in altering the runoff patterns in the basin. These findings highlight the importance of sustainable land-use planning and water resource-management practices in the PSRB to mitigate the negative impacts of urbanization on the hydrological cycle and to enhance the resilience of the region’s water resources.

A região sul do estado de Minas Gerais (RSMG) possui topografia acidentada tendo como destaque a Serra da Mantiqueira. Devido a essa característica peculiar, em geral, os modelos climáticos com resoluções horizontais grosseiras não conseguem representar adequadamente o clima da região. A fim de identificar o impacto da topografia da RSMG na temperatura do ar, precipitação e circulação atmosférica, foram realizados dois experimentos numéricos, em alta resolução (12 km), com o Regional Climate Modelversion 4 (RegCM4): um denominado de controle (CTRL) e outro em que a topografia foi removida (STOPO). O período das simulações foi de novembro de 2008 a fevereiro de 2009. A temperatura do ar simulada no experimento CTRL foi validada através de comparação com a Climate Forecast System Reanalysis (CFSR), enquanto que a precipitação com as estimativas do Tropical Rainfall Measuring Mission (TRMM). Ambas as variáveis simuladas também foram comparadas com dados medidos em estações meteorológicas convencionais do Instituto Nacional de Meteorologia (INMET). Entre os resultados têm-se que a ausência da topografia conduz a maiores temperaturas médias mensais e acumulados de precipitação, bem como a desconfiguração da circulação de brisa de vale e montanha sobre a RSMG. Palavras-chave: Sul de Minas Gerais. Topografia. Modelo Climático. Topography influence of the Southern Region of Minas Gerais State on the atmospheric variables simulated by RegCM4 A B S T R A C T The Southern Region of the Minas Gerais State (RSMG) has rugged topography, such as the Serra da Mantiqueira. Due to this peculiar feature, in general, climate models with coarse horizontal resolutions may not represent adequately the climate of this region. To identify impacts of RSMG topography on air temperature, precipitation and atmospheric circulation, two high resolution (12 km) numerical experiments were performed using the Regional Climate Modelversion 4 (RegCM4): a control simulation (CTRL) and a second one with removed topography (STOPO). The simulation period was from November 2008 to February 2009. Simulated air temperature fields from CTRL were validated against Climate Forecast System Reanalysis (CFSR), and rainfall against Tropical Rainfall Measuring Mission (TRMM) ground estimates. Simulated variables were also compared with data from conventional meteorological stations of the National Institute of Meteorology (INMET). Among the results we highlight that average monthly temperatures and precipitation increase, and the circulations of valley and mountain breeze are obliterated with suppressed topography.