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

Drought events are critical environmental threats that yield several socioeconomic impacts. Such effects are even more relevant for South America (SA) since different activities essential for the continent, such as agriculture and energy generation, depend highly on water resources. Thus, this study aimed to evaluate future changes in precipitation and hydrological drought occurrence in SA through climate projections from eight global climate models (GCMs) of CMIP6. To this end, statistical downscaling was applied to the projections obtained using the quantile delta mapping technique, and the method proved to be efficient in reducing systematic biases and preserving GCMs’ trends. For the following decades, the results show considerable and statistically significant reductions in precipitation over most of SA, especially during the austral spring, with the most intense signal under the SSP5-8.5 forcing scenario. Furthermore, GCMs showed mixed signals about projections of the frequency and intensity of drought events. Still, they indicated agreement regarding the increased duration and severity of events over the continent and a substantial proportion of moderate and severe events over most of Brazil during the 21st century. These results can be helpful for better management of water resources by decision-makers and energy planners.

At the end of June 2020, an explosive extratropical cyclone was responsible for an environment in which a squall line developed and caused life and economic losses in Santa Catarina state, southern Brazil. The aims of this case study are the following: (a) to describe the drivers of the cyclogenesis; (b) to investigate through numerical simulations the contribution of sea–air interaction to the development of the cyclone as an explosive system; and (c) to present the physical properties of the clouds associated with the squall line. The cyclogenesis started at 1200 UTC on 30 June 2020 on the border of southern Brazil and Uruguay, having a trough at middle-upper levels as a forcing, which is a common driver of cyclogenesis in the studied region. In addition, the cyclone’s lifecycle followed Bjerknes and Solberg’s conceptual model of cyclone development. A special feature of this cyclone was its fast deepening, reaching the explosive status 12 h after its genesis. A comparison between numerical experiments with sensible and latent turbulent heat fluxes switched on and off showed that the sea–air interaction (turbulent heat fluxes) contributed to the cyclone’s deepening leading it to the explosive status. The cold front, which is a component of the cyclone, favored the development of a pre-frontal squall line, responsible for the rough weather conditions in Santa Catarina state. While satellite images do not clearly show the squall line located ahead of the cold front in the cyclone wave due to their coarse resolution, radar reflectivity data represent the propagation of the squall line over southern Brazil. On 30 June 2020, the clouds in the squall line had more than 10 km of vertical extension and a reflectivity higher than 40 dBZ in some parts of the storm; this is an indicator of hail and, consequently, is a required condition for storm electrification. In fact, electrical activity was registered on this day.

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Drought events are evident effects of climate change around the globe and yield several socio-economic impacts. Such effects are even more relevant for South America (SA) since different activities essential for the continent, like agriculture and energy generation, depend highly on water resources. Thus, this study aimed to evaluate future changes in precipitation and hydro-logical droughts occurrence in SA through climate projections from eight global climate models (GCMs) of CMIP6. To this end, statistical downscaling was applied to the projections with the Quantile Delta Mapping technique, and the method proved to be efficient in reducing systematic biases and preserving GCMs’ trends. For the following decades, the results show considerable and statistically significant reductions in precipitation over most of SA, especially during the austral spring, with the most intense signal under the SSP5-8.5 forcing scenario. Furthermore, GCMs showed mixed signals about projections of the frequency and intensity of drought events. Still, they indicated agreement regarding the increase in duration and severity of events over all of SA and a substantial proportion of moderate and severe events over most of Brazil during the 21st century. These results can be helpful for better management of water resources by deci-sion-makers and energy planners.