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The Southern Annular Mode (SAM) is an extratropical pattern that influences the climate of all Southern Hemisphere. However, the variability of this mode is an active area of research. The influence of lower frequency modes on SAM is a path to better knowledge about this pattern. The relationship between Quasi-Biennial Oscillation (QBO) and SAM’s counterpart in the Northern Hemisphere (Northern Annular Mode) has been addressed by previous work. Still, few studies focus on the association between QBO and SAM. The goal of this work was to evaluate the possible QBO-SAM relationship through statistical analyses. This association was investigated by comparing QBO and SAM indices, the latter on different levels of the troposphere and stratosphere, for the 1981-2010 period. The wavelet analysis showed that the SAM indices for troposphere and stratosphere presented variability in many scales, including a two-year band. Cross-wavelets techniques between QBO and SAM ratified that this relation has a complex interaction. There was a significant common high power around the two-year band, with lags varying over the analyzed period, including no lag. Further analysis without lag confirmed previous studies, indicating that the negative (positive) SAM phase is more frequent for easterly (westerly) QBO. However, this was not valid for all months. Some additional analysis suggested that the upward wave propagation to the stratosphere for each QBO phase changes the stratospheric jet and, consequently, the SAM phase.

This work aimed to identify the synoptic conditions associated with the Frontal Systems (FSs) passage that causes intense winds in the Santos Basin (SB). Furthermore, the atmospheric characteristics of the FSs, which generated intense (INTW) and moderate (MODW) winds in the studied area were identified. For this purpose, INTW and MODW composites of FSs episodes were elaborated. First, the INTW and MODW cases were selected from the 10 meters wind intensity (W10M) observed in the Santos buoy, belonging to Brazil's National Buoys Program. Satellite images and synoptic surface charts were analyzed to identify the synoptic systems responsible for INTW and MODW in the Santos buoy, keeping only the cases generated by FSs. From the comparison between the INTW and MODW composites, it was possible to observe in INTW: i) a stronger pressure gradient over the SB, which caused the intense winds registered in the buoy; ii) a baroclinic trough at medium and high levels reaching the SB region, and located westward of the surface system; iii) stronger 1000-500 hPa layer thickness and dew point temperature gradients over the continent, reaching the SB region, indicating the position of the FS and iv) a colder and drier air mass over southern Brazil. In large scale, the Rossby wave tracings were analyzed, where different wavenumbers were noticed for each composite. In INTW, the wavenumber was 2, while in MODW, it was 2 and 3. For case studies of INTW and MODW, the main characteristics found in the respective composites were observed.

This paper analyzed the anomalous rainy austral summer of 2020 over the southeastern region of Brazil (SEB), investigating its possible mechanisms. The SEB experienced dry summers in the years before 2020; however, the austral summer of 2020 in this region was the wettest since 1991. A wave train starting from the Indian Ocean to the Pacific Ocean, plus a wave train from the tropical north (U-shape), and another from the western equatorial Pacific (PSA-like) contributed to an anomalous anticyclonic circulation at high levels southward South America. This merged wave train continued its path with an anomalous cyclonic circulation over the southern region of Brazil and the state of Sao Paulo, and anticyclonic northward, enhancing (inhibiting) convection over SEB (southern Brazil). Besides, the Southern Annular Mode (SAM) pattern was in a positive phase, and there were negative sea surface temperature (SST) anomalies near SEB and Argentina, contributing for the configuration over the continent. Comparisons of the main differences between the austral summer of 2019 (dry) and the summer of 2020 show there was no anomalous divergence at high levels over the Indian Ocean in 2019, triggering a wave train from this region to the Pacific. The two wave trains from the Pacific merged in an anomalous anticyclonic circulation over the southeastern Pacific, near the South American coast. The SAM pattern was neutral in 2019; however, there were positive SST anomalies near SEB, southern Brazil and Argentina coastal. The South Atlantic SST and the wave trains generated an anticyclonic anomalous circulation over the southern Region of Brazil and cyclonic northward, in opposition to the 2020 configuration.

Chuvas intensas sao eventos de baixa previsibilidade, mas com grande impacto social, causando prejuizos tanto financeiros quanto humanos. Neste interim, os indices de instabilidade sao uma boa ferramenta para auxiliar os previsores, pois podem indicar se o ambiente atmosferico e ou nao propicio para a formacao de nuvens profundas. Neste trabalho, foi analisado o comportamento de alguns indices de instabilidade para diferentes taxas de precipitacao. Foram utilizados os dados SYNOP (1996 a 2014), provenientes de estacoes meteorologicas das Regioes Sul e Sudeste do Brasil, para as quais tambem estavam disponiveis os dados das sondagens atmosfericas. Os dados coletados foram categorizados em tres intervalos de classe de interesse de acordo com os registros dos acumulados pluviometricos: acima de 60 mm/dia (classe 1 – chuva intensa), entre 60 mm/dia e 5 mm/dia (classe 2 – chuva moderada) e abaixo de 5 mm/dia (classe 3 – chuva fraca/nao chuva). Os eventos de chuvas intensas (classe 1) mais frequentes ocorreram associados a atuacao de Sistemas Frontais, desta forma optou-se por selecionar, para as tres classes, eventos de chuva que estivessem associados a esse sistema. Ao final, 12 eventos de chuvas intensas foram identificados. De forma a uniformizar as classes, foram selecionadas tambem 12 eventos das classes 2 e 3, onde todos os casos com chuva (fraca e moderada) tambem estavam associados a Sistemas Frontais. Os casos sem chuva (precipitacao igual a zero) da classe 3 nao tinham nenhum sistema associado. Foram calculados cinco indices de instabilidade para as tres classes de precipitacao (12 eventos em cada). Os indices K, Total Totals (TT) e Severe Weather Threat (SWEAT) se destacaram como bons indicadores nos casos de chuvas moderadas a intensas (classes 1 e 2). Os indices Lifted Index (LI), Indice Showalter (IS) e Convective Potential Available Energy (CAPEv), entretanto, nao caracterizam bons resultados para os eventos de chuva analisados (associados com sistemas frontais). A analise combinada entre os indices K, TT e SWEAT tambem se mostrou eficiente como um indicador atmosferico para a ocorrencia de chuvas moderadas a intensas.

Padroes de teleconexoes, tais como El Nino-Oscilacao Sul (ENOS) e o Modo Anular Sul (SAM) afetam a circulacao e, consequentemente, o clima da America do Sul. Alguns trabalhos mostram que esses padroes podem estar relacionados a variacoes na ocorrencia de sistemas transientes, tais como, as frentes frias. A extensao de gelo marinho antartico tambem afeta a circulacao em todo o Hemisferio Sul. Porem, nao ha um estudo analisando os impactos em conjunto do ENOS, do SAM e do gelo marinho antartico na atuacao das frentes frias na America do Sul. Desta forma, o objetivo deste trabalho foi avaliar a frequencia de frentes frias na America do Sul nos anos com anomalias do gelo marinho antartico nos mares de Bellingshausen-Amundsen (MBA) e Weddel (MWD) em conjunto com a atuacao das fases do SAM e do ENOS. Os resultados apresentam diferenca nas atuacoes das frentes entre o continente e o Oceano Atlântico adjacente. Em geral, para ambos os mares analisados, e possivel notar a atuacao da La Nina e SAM positivo em todas as analises de frequencias maximas de frentes frias sobre o oceano, variando somente a extensao do gelo marinho. No continente, o El Nino junto com a fase negativa do SAM domina as maximas frequencias de frentes em ambas as extensoes de gelo marinho no MBA e combinado com maxima extensao de gelo marinho no MWD. As diferencas entre o oceano e continente indicam que os tres fatores (SAM, ENOS e gelo marinho) influenciam na trajetoria das frentes, mais meridional e continental ou entao mais maritima.

Este artigo tem como objetivo analisar relacoes entre as fases de padroes de teleconexoes tropicais, subtropicais e extratropicais e as extensoes de gelo marinho antartico no Mar de Weddell (MW). Busca-se melhor compreensao acerca da variabilidade do gelo marinho e das interacoes entre a criosfera e a atmosfera, alem de prover dados para estudos sobre previsoes e variabilidade climaticas. Este artigo analisa setembro, o mes com a maior cobertura de gelo marinho no Mar de Weddell. Utilizou-se os indices mensais dos padroes Modo Anular do Sul ( Southern Annular Mode – SAM), Modo Meridional do Atlântico ( Atlantic Meridional Mode – AMM) e Gradiente Subtropical do Atlântico Sul (GSA). O indice SAM foi calculado atraves da Funcao Ortogonal Empirica nas anomalias de altura geopotencial em 700 hPa na regiao ao sul de 30oS, o indice AMM foi extraido do National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) e o indice GSA foi criado a partir dos dados de temperatura da superficie do mar (TSM) do ERSSTv5 do National Oceanic and Atmospheric Administration (NOAA). Nas avaliacoes conjuntas, as combinacoes de fases que se relacionaram as maiores extensoes de gelo foram SAM negativo/AMM positivo e SAM negativo/GSA positivo enquanto as que se associaram as menores extensoes foram as de sinais opostos. As correlacoes do SAM com o gelo marinho sao negativas e dos indices AMM e GSA com o gelo marinho sao positivas, mostrando coerencia com os resultados apresentados nos compostos e nos graficos boxplots. Extreme Antarctic Sea Ice In The Weddell Sea And Links With Teleconnection Patterns Of Climate Variability ABSTRACT This article examines the links between the phases of teleconnection patterns of climate variability and the Weddell’s Sea ice extent. The goal is to understand better the sea ice variability and connections between the cryosphere and the atmosphere. This paper focuses on September, the month with the largest sea ice cover in the Weddell Sea. The Southern Annular Mode (SAM), the Atlantic Meridional Mode (AMM) and the Atlantic Subtropical Gradient (ASG) monthly indices were used. The SAM index was calculated through Empirical Orthogonal Function in the geopotential height anomalies of 700 hPa. The AMM index was obtained by the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR). The ASG index was created using sea surface temperature (SST) data obtained by the National Oceanic and Atmospheric Administration (ERSSTv5/NOAA) through the difference of SST anomalies averaged at two distinct areas situated in the Subtropical Atlantic Ocean. Considering the effect of these indices combined, the negative SAM/positive AMM phase and the negative SAM/positive ASG phase were associated with maximum Antarctic sea ice extents. The opposite combinations of indices were related with minimum Antarctic sea ice extents. The correlations between the SAM and the sea ice extent are negative and between AMM and ASG with the sea ice extent are positive. These results are coherent with the results presented in the composite maps and the boxplots charts. Keywords: Teleconnection patterns, climate variability, antarctic sea ice, Weddell Sea.

The goal of this paper is to study month-to-month impacts of Southern Hemisphere Annular Mode (SAM) phases over South America (SA). Composite analyses were performed excluding ENSO years. Southeastern SA (SESA), part of Southeastern and Central-West of Brazil seem to be more affected by SAM. However, SAM influences are different for each month, and there are also differences of the influences between SAM phases (not always opposite). For air temperature, March, May, July, August, September, and November show positive (negative) anomalies affecting regions cited above during the negative (positive) SAM phase. Although, the coverage of these anomalies is different among these months. February and December present a temperature anomaly dipole, with positive (negative) anomaly at SESA and negative (positive) northward, in the negative (positive) SAM phase. January has a different behavior compared with other months but also presents a nearly opposite signal between SAM phases. Precipitation anomalies composites indicate a weakening (strengthening) of South Atlantic Convergence Zone configuration at negative (positive) SAM phase (November-January and March). SESA region shows positive (negative) precipitation anomalies at negative (positive) SAM phases, during March-June and December. Nevertheless, in October, SAM oppositely influences this region. A case study (January 2017 - negative SAM - neutral ENSO) shows great similarity with the precipitation composites, ratifying the results. However, for temperature, the coastal region is the only which presents similarity with the composites. The goal of this paper is to study month-to-month impacts of Southern Hemisphere Annular Mode (SAM) phases over South America (SA). Composite analyses were performed excluding ENSO years. Southeastern SA (SESA), part of Southeastern and Central-West of Brazil seem to be more affected by SAM. However, SAM influences are different for each month, and there are also differences of the influences between SAM phases (not always opposite). For air temperature, March, May, July, August, September, and November show positive (negative) anomalies affecting regions cited above during the negative (positive) SAM phase. Although, the coverage of these anomalies is different among these months. February and December present a temperature anomaly dipole, with positive (negative) anomaly at SESA and negative (positive) northward, in the negative (positive) SAM phase. January has a different behavior compared with other months but also presents a nearly opposite signal between SAM phases. Precipitation anomalies composites indicate a weakening (strengthening) of South Atlantic Convergence Zone configuration at negative (positive) SAM phase (November-January and March). SESA region shows positive (negative) precipitation anomalies at negative (positive) SAM phases, during March-June and December. Nevertheless, in October, SAM oppositely influences this region. A case study (January 2017 - negative SAM - neutral ENSO) shows great similarity with the precipitation composites, ratifying the results. However, for temperature, the coastal region is the only which presents similarity with the composites.

Southeastern Brazil is a highly industrialized and populated region which largely contributes to the country's economy. Extreme precipitation over this region can cause floods and landslides occurrences or lack of precipitation that can affect many sectors of economy. The objective of this work is to identify atmospheric characteristics associated with austral summer extreme precipitation over part of Southeastern Brazil. The atmospheric characteristics obtained from wet and dry composites suggest that extreme precipitation was associated with anomalous circulation over the region, forced by a PSA-like wavetrain intensified by the Southern Annular Mode. Copyright © 2010 Royal Meteorological Society