The precipitation pattern of the State of Rio Grande do Sul (RS) is changing, indicating an increase, although there are long periods of drought. Several studies indicate the influence of climate variability modes on RS precipitation. This work analyzes the influence of the Southern Annular Mode (SAM) and the El Niño -Southern Oscillation (ENSO) on precipitation anomalies (PP) of the Rio Grande do Sul Coastal Plain (RGSCP), dividing it into three regions: south, central and north. Contingency tables were used to correlate the indices, classifying them as neutral, below ou above the mean. To statistical significance we used percentage correctly classified with which the Student's t was aplied for each region. The PP of the RGSCP and the south coast have correlation with the ENSO and SAM; the central only with SAM. The PP of the north is not correlated to either index. Periods with more than 5 months of PP, SAM and ENSO anomalies were identified. Below average events were majority. The results indicate greater influence of SAM + and La Niña. The trend towards SAM+ and intensification of ENSO, could increase the frequency of droughts in RGSCP. In addition, it was possible to interpret that the geographical differences of the RGSCP can influence the results of precipitation totals. This work contributes to the understanding of the effects of the new trends of climatic variability under regional and geographical aspects. RESUMOO padrão de precipitação do estado do Rio Grande do Sul (RS) esta mudando, indicando aumento, ainda que se observe longos períodos de seca. Diversos estudos apontam influencia de modos de variabilidade climática na precipitação do RS. Este trabalho analisa a influência do Modo Anular do Hemisfério Sul (SAM) e do El Niño -Oscilação Sul (ENOS), nas anomalias de precipitação (PP) da Planície Costeira do Rio Grande do Sul (PCRGS), a dividindo em três regiões: sul, central e norte. Tabelas de contingência foram utilizadas para correlacionar os índices, os classificando como neutros, abaixo ou acima da média. Para significância estatística utilizamos o percentual corretamente classificado, com o qual se aplicou o teste t de Student para cada região. As PP da PCRGS e da costa sul possuem correlação com o ENOS e SAM; a central apenas com o SAM. As PP do norte não são correlacionadas há nenhum dos dois indices. Períodos com mais de 5 meses de PP, SAM e ENOS anômalos foram identificados. Eventos abaixo da média foram maioria. Os resultados indicam maior influência SAM+ e La Niña. A tendência ao SAM+ e intensificação do ENOS, poderá aumentar a frequência de secas na PCRGS. Além disso, foi possível interpretar que as diferenças geográficas da PCRGS podem influenciar nos resultados dos totais de precipitação. Este trabalho contribui para a compreensão dos efeitos das novas tendências da variabilidade climática sob aspecto regional e geográfico.Palavras-chave: Ambiente costeiro; Padrões de teleconexão; Clima regional.RBRH, Porto Alegre, v. 23, e14, 2018Precipitation anomalies in the Brazilian southern coast r...

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A morfologia de canais é resultado do ambiente em que se encontram, assim como de todas variáveis físicas atuantes. Se a desembocadura está situada em zonas costeiras, a tendência à instabilidade é amplificada pelo próprio meio. Neste artigo são apresentados os resultados do estudo morfodinâmico do canal de comunicação entre a Lagoa do Peixe e o Oceano Atlântico, localizado no Parque Nacional da Lagoa do Peixe, litoral médio do Rio Grande do Sul, Brasil. Também é medida a variabilidade da linha de praia adjacente ao parque. Com o objetivo de determinar a classifica- ção do canal e sua dinâmica natural, foram utilizados uma série de 47 anos de imagens Landsat (1973 – 2009), dados de precipitação da Agencia Nacional de Águas e equações. A interpretação da série temporal e os cálculos das médias de precipitação permitiram descrever o canal da Lagoa do Peixe como um canal de maré, com mecanismo de assoreamento morfodinâmico influenciado pelo regime de precipitação pluviométrica. Os resultados das equações indicaram como fatores determinantes à sua oclusão o prisma de maré e transporte e deposição sedimentar em frente a desembocadura, associados à deriva litorânea de padrão bidirecional da área de estudo. Sua desembocadura possui caráter intermitente e é instável quanto ao seu posicionamento e geometria. A mobilidade da linha de praia adjacente ao Parque Nacional da Lagoa do Peixe foi verificada pelo método de pontos extremos, pixel a pixel, entre duas imagens Landsat de mesmo mês, uma de 1987 e outra de 2009, sendo constatada erosão ao sul da desembocadura do canal da Lagoa do Peixe e acreção ao norte da mesma.

Este estudo examina a relação entre anomalias da circulação atmosférica antártica e uma ciclogênese explosiva na Bacia do Prata na primavera de 2016. A instabilidade se iniciou na Bacia do Prata, evoluindo para um ciclone extratropical que se deslocou para o Oceano Atlântico com fortes ventos sustentados gerando uma intensa maré de tempestade no litoral sul do Brasil. Para identificar a origem da ciclogênese, foram reconstruídos campos de altura geopotencial, vetores vento u e v e temperatura em 925, 500 e 200 hPa da primavera e dos dias do evento (25 a 28/outubro) para o Hemisfério Sul com dados ERA/Interim. A associação entre o Modo Anular do Hemisfério Sul, padrão de onda três, ventos, altura e direção de ondas possibilitaram relacionar essa ciclogênese explosiva as anomalias de circulação atmosférica na região antártica. Palavras-chave: variabilidade climática, aquecimento global, teleconexões climáticas, ENOS, SAM   Abstract This study examines the relationship between Antarctic atmospheric circulation anomalies and an explosive cyclogenesis in the La Plata Basin in the 2016 spring. This instability began in the La Plata Basin, evolving into an extratropical cyclone, moved to the Atlantic Ocean with strong sustained winds generating an intense storm surge in the Brazilian southern coast. We reconstructed the fields of geopotential height, vectors wind u and v and temperature in 925, 500 and 200 hPa of the spring and the days of the event (25 to 28 / October) for the Southern Hemisphere with ERA / Interim data to identify the origin of the cyclogenesis. The association between the Southern Annular Mode, zonal wave three pattern, winds, height and wave direction made it possible to relate this explosive cyclogenesis to the atmospheric circulation anomalies in the Antarctic region. Keywords: climate variability, global heat, climate teleconnections, ENSO, SAM

Here we analyze the trends of rainfall and the frequency of rainy days over the Brazilian Cerrado between 1960 and 2021 in four distinct periods according to the seasonal patterns over the region. We also evaluated trends in evapotranspiration, atmospheric pressure, winds, and atmospheric humidity over the Cerrado to elucidate the possible reasons for the detected trends. We recorded a significant reduction in rainfall and frequency of rainy days in the northern and central Cerrado regions for all periods except at the beginning of the dry season. The most pronounced negative trends were recorded during the dry season and the beginning of the wet season, where we recorded reductions of up to 50% in total rainfall and the number of rainy days. These findings are associated with the intensification of the South Atlantic Subtropical Anticyclone, which has been shifting atmospheric circulation and raising regional subsidence. Moreover, during the dry season and the beginning of the wet season, there was a reduction in regional evapotranspiration, which also potentially contributed to the rainfall reduction. Our results suggest an expansion and intensification of the dry season in the region, potentially bringing broad environmental and social impacts that transcend the Cerrado boundaries.

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Abstract. Stable water isotopes and accumulation data extracted from polar ice/firn cores provide valuable climate information. Here, we present novel isotopic and accumulation time series from an upstream area of the Möller Ice Stream (MIS) basin, Weddell Sea Sector (WSS), Antarctica – a Brazilian research area (84°00’00’’S; 79°29’39’’W; 1276 m a.s.l.). Our purpose was to understand the depositional history and investigate how much the recent climate signal (21st century) is stored in the shallowest ice sheet layers in this area. Therefore, we crossed the isotopic (δ18O, δD, and d-excess) and snow accumulation data of two shallow firn cores (both ⁓9.0 m deep) with glaciological information, local and regional meteorological data (both ERA5 and AWS), indices of large-scale atmospheric modes (as SAM and ENSO) and the Amundsen Sea Low (ASL). The isotopic records cover 16 years (from 1999 to 2015-austral summer) and the accumulation records cover 20 years (from 1999 to 2018). We find that interannual δs variability is strongly explained by changes in the phase of the SAM (r = 0.74; p < 0.05; α = 0.05) and, consequently, also by changes in pressure of both the WSS (r = -0.57; p < 0.05; α = 0.05) and the ASL (r = -0.56; p < 0.05; α = 0.05). The regional temperature in WSS (r = 0.50; p < 0.05; α = 0.05) and Antarctica Peninsula (r = 0.70; p < 0.05; α = 0.05), as well as the sea ice concentration in the Weddell Sea (r = -0.49; p = 0.05; α = 0.05) are other factors that measurably influence the δs in the study area. In the period covered by our study, the rarest and strongest wind events (SWE; > ⁓15 m/s) and extreme precipitation events (EPE) oscillate almost completely out of phase, and this relationship is largely explained by the sub-decadal changes in the SWE-ENSO relationship and by the SAM variability. This oscillatory pattern between SWE and EPE justifies the non-temporally stable correlation between δs and local temperature in the study area. For the period of 2013–2018, we show that the trigger to start accumulating snow on the studied site is the occurrence of a range of EPE in a short time or of the one EPE with higher snowfall rates and that, the low snowfall events are hardly ever preserved. Our snow accumulation composite record shows that the SWE-EPE seesaw governs the snow accumulation in the upstream area of the MIS basin in the 1999–2018 period. When the frequency of SWE increases and EPE decreases, the local snow accumulation increase. In contrast, in the opposite scenario, the accumulation approaches the forecast precipitation data indicating that the influence of blowing snow and wind drift decreases. Because of this relation, incredibly there was a significant decrease in snow accumulation in the study area in the 1999–2018 period due to an increase in EPE in recent years. Probably, in a scenario of future warming, the persistence of SAM positive trend, and the EPE increase due to intensification of wetter and warmer air masses incursions by the WSS such a relationship will change. Our results indicate that both isotopic compositions and snow accumulation are strongly influenced by large-scale modes of climate variability in the MIS basin inland. Furthermore, they also provide valuable information to understand mass balance at the basin scale in the WSS. We recommend more shallow drills and snow pits in this site to construct the best composite record to reconstruct these atmospheric circulation patterns and solve challenges regarding the topographic effect.