Variabilidade Intrassazonal Extrema da Temperatura do ar à Superfície na Península Antártica

A Península Antártica (PA) é uma das regiões da Terra onde o aquecimento foi mais acelerado nos últimos 50 anos. Há indícios de que esta tendência esteja associada, em parte, ao aumento da atividade intrasazonal (IS) tropical. Utilizando dados de estações, este estudo mostrou que a variabilidade da temperatura do ar à superfície (Tsup) sobre a PA apresenta um pico estatisticamente significativo na escala IS (78 dias). A influência da Oscilação Madden-Julian (MJO) sobre os eventos IS da Tsup na PA foi quantificada: mais de 60% dos eventos foram associados à MJO, via trem de ondas de Rossby com periodicidade em torno de 30-40 dias. Portanto, outros mecanismos precisam ser investigados para explicar a variabilidade IS da Tsup na PA não associada à MJO (NMJO). Tanto os eventos NMJO quanto o total de eventos (MJO + NMJO) foram mais frequentes na primavera. Além disso, nos últimos 12 anos analisados (1998-2009) houve uma maior frequência de eventos MJO do que NMJO, principalmente na primavera e no inverno

Análise de Agrupamento da Temperatura do ar no Sul do Brasil entre 1961-2011

The economy in the southern Brazil is based on agriculture and livestock sectors which, in turn, depend on the meteorological parameters variability, such as precipitation and temperature. In this study was performed a climatological analysis of the air temperature in the southern Brazil during 1961-2011, using the cluster analysis and thereby providing information about the temperature spatial variability on the region

SPATIAL VARIABILITY OF AIR TEMPERATURE IN SOUTHERN BRAZIL BETWEEN 1961-2011

Temperature is one of the most important variables used in climate studies. Changes in its time series can cause various social and political impacts, affecting diverse sectors of society, such as agriculture, for example. Southern Brazil is a region that relies heavily on agriculture, contributing to national production. Therefore, it is important to check the air temperature characteristic, i.e., its spatial pattern in this region. For this, daily data of minimum and maximum temperature of the air of the National Institute of Meteorology were used in the period from 1961 to 2011. The statistical technique of cluster analysis was applied to identify the homogeneous regions of temperature and the boxplot for the characterization of each an. In general, the results showed maximum values of temperatures in the west of Rio Grande do Sul. The regions of minimum temperatures presented a more homogenous pattern, with averages around 15 ºC. The regions of the maximum temperatures showed average values oscillating between 22 ºC and 28 ºC.Temperature is one of the most important variables used in climate studies. Changes in its time series can cause various social and political impacts, affecting diverse sectors of society, such as agriculture, for example. Southern Brazil is a region that relies heavily on agriculture, contributing to national production. Therefore, it is important to check the air temperature characteristic, i.e., its spatial pattern in this region. For this, daily data of minimum and maximum temperature of the air of the National Institute of Meteorology were used in the period from 1961 to 2011. The statistical technique of cluster analysis was applied to identify the homogeneous regions of temperature and the boxplot for the characterization of each one. In general, the results showed maximum values of temperatures in the west of Rio Grande do Sul. The regions of minimum temperatures presented a more homogenous pattern, with averages around 15 ºC. The regions of the maximum temperatures showed average values oscillating between 22 ºC and 28 ºC

A RELAÇÃO ENTRE A POLUIÇÃO DO AR E AS PRINCIPAIS VARIÁVEIS CLIMATOLÓGICAS NO MUNICÍPIO DE CANOAS-RS

Nas últimas décadas, junto com o crescente aumento do número de veículos no Brasil, também tem crescido a preocupação com fatores ligados à poluição e suas consequências para a sociedade. Nesse contexto, o presente trabalho teve por objetivo aplicar técnicas estatísticas de análise multivariada aos dados de poluentes do ar e variáveis meteorológicas para investigar a relação entre estes componentes. Além disso, foram ajustados modelos de Previsão de Séries Temporais para os índices de poluição do ar, utilizando as variáveis climatológicas como exógenas aos modelos, com a finalidade de comparar o desempenho dos modelos. Os dados foram coletados junto ao Instituto Nacional de meteorologia (INMET) (variáveis climatológicas) e Fundação Estadual de Proteção Ambiental (FEPAM) (poluentes do Ar) referente ao município de Canoas-RS, durante o ano de 2014. Os resultados da análise de cluster mostram a formação de dois grupos bem definidos: O cluster 1 reúne as variáveis mais próximas (O3, Insolação, Evaporação, Temperatura Mínima e Temperatura Máxima), o cluster 2, as variáveis mais próximas (SO2, CO, PM10). Ajustaram-se modelos de previsão de Séries Temporais para a variável O3, usando as demais variáveis do grupo 1 como exógenas. O modelo de Série Temporal que permite a inclusão de variáveis exógenas (SARIMAX), obteve melhores resultados de previsão em relação aos seus concorrentes (SARIMA e da classe de Alisamento Exponencial). Conclui-se que o uso conjunto de modelos de análise multivariada e séries temporais proporciona melhores resultados de previsão. Destaca-se a ampla possibilidade de utilização das técnicas conjuntas de análise multivariada e séries temporais, podendo ser utilizadas como ferramenta de apoio nas tomadas de decisão

Variabilidade Hidroclimática da Bacia Hidrográfica do Rio Negro: Um Estudo de Caso para a Porção Brasileira

In this article we carried out a hydroclimatological characterization of the upper reaches of the Rio Negro Basin, located in the Brazilian portion. We used rainfall and streamflow data from the Instituto Nacional de Meteorologia (INMET) and the Agência Nacional de Águas (ANA) in the 1995-2014 period, collected at different points surrounding the watershed. From the data analysis, we can identify that the average annual precipitation over the basin varies between 1440 and 1480mm. The annual average streamflow was approximately 538,7mm, corresponding to a runoff coefficient of 38%. The accumulated rainfall and streamflow series showed that, as of mid-year 2004, there was a significant reduction of the accumulated streamflow, probably caused by an increase in water demand for agricultural irrigation due to lower volumes of rainfall. Pre-2005 runoff coefficient showed an interannual oscillation between 36% and 42%, after 2005 the runoff coefficient systematically decreased from 45% to 35%. This reduction suggests an increase in the extraction of water for irrigation which consequently favors greater crop evapotranspiration in a period with slightly lower annual precipitation (2005-2014) compared to the previous period (1995-2004).Neste trabalho realizou-se a caracterização hidroclimatológica do trecho superior da Bacia Hidrográfica do Rio Negro, localizado na porção brasileira. Para isso foram utilizados dados de precipitação e vazão fluvial provenientes do Instituto Nacional de Meteorologia(INMET) e da Agência Nacional de Águas (ANA) do período de 1995 a 2014, coletados em diferentes pontos no entorno dabacia hidrográfica. A partir da análise dos dados, pode-se identificar que a média anual da precipitação sobre a bacia varia entre1440 e 1480mm. A vazão média anual foi de aproximadamente 538,7mm, o que corresponde a um coeficiente de escoamento de38%. As séries de precipitação e vazão acumuladas mostraram que, a partir de meados do ano de 2004, houve uma significativaredução da vazão acumulada, ocasionada provavelmente pelo aumento na demanda hídrica para irrigação agrícola devido aosmenores volumes de precipitação. O coeficiente de escoamento pré-2005 mostrou uma oscilação interanual entre 36% e 42%, após2005 o coeficiente de escoamento diminui sistematicamente de 45% para 35%. Esta redução sugere um aumento na captação de água para irrigação que consequentemente favorece a maior evapotranspiração das culturas num período com precipitação anuallevemente menor (2005-2014) em comparação ao período prévio (1995-2004)

Intraseasonal Extreme Temperature Anomalies in the Antarctica Peninsula and Atmospheric Mechanisms

O clima na Antártica tem um papel fundamental no balanço de energia global. Estudos sugerem que a atividade convectiva tropical e a circulação estratosférica exercem um papel importante sobre a circulação atmosférica nos extratrópicos. A temperatura do ar é uma variável sensível às mudanças na circulação, no entanto, ainda não foi investigada a importância da escala intra-sazonal na sua variabilidade sobre a Antártica. Neste trabalho estudou-se a variabilidade intra-sazonal da temperatura do ar a superfície na região da Península Antártica enfocando as interações trópicos-extratrópicos e troposfera-estratosfera na modulação de eventos extremos de temperatura naquela região. Foram utilizados dados diários de estações localizadas nos setores leste e oeste da Península Antártica no período de 1986-2002. A análise espectral dos dados ressaltou a importância da escala intra-sazonal na variabilidade da temperatura na Península Antártica, principalmente no período de inverno, primavera e verão. Baseado nestes resultados, os dados foram filtrados na escala intra-sazonal (banda de 20-100 dias) e posteriormente, obteve-se os extremos intra-sazonais frios e quentes para as três estações do ano, através dos quartis da distribuição dos dados. Os eventos extremos intra-sazonais de temperatura (EIT) foram mais intensos no inverno e mais fracos no verão. As características da circulação atmosférica intra-sazonal associada aos EIT foram obtidas através de composições defasadas das anomalias intra-sazonais da altura geopotencial em 200 hPa, vento zonal em 200 hPa e vento meridional em 850 hPa. Nas três estações do ano, observou-se nos eventos extremos intra-sazonais frios (EIF) a persistência de anomalias ciclônicas em altos níveis, a diminuição da intensidade do jato polar e uma advecção de ar frio em baixos níveis sobre a região de estudo. Uma situação oposta foi verificada nos eventos extremos intra-sazonais quentes (EIQ). De forma geral, observou-se um trem de ondas entre latitudes médias e altas no Hemisfério Sul (HS) durante os EIT, particularmente no inverno e primavera. Esta configuração mostrou-se semelhante a tele-conexão conhecida como Pacífico-Sul Americano (PSA). O papel do modo anular do HS sobre os EIT foi analisado através do cálculo de Funções Ortogonais Empíricas das anomalias intra-sazonais da altura geopotencial em 700 hPa ao sul de 20ºS. Sua estrutura foi mais intensa (mais fraca) nos EIF (EIQ) de inverno sobre a região de estudo. A interação troposfera-estratosfera no controle dos EIT foi investigada através do Fluxo Eliassen-Palm. Nas composições das anomalias intra-sazonais deste fluxo (EPIS), observou-se durante os EIF (EIQ) de inverno, um aumento da atividade de onda da baixa estratosfera (alta troposfera) para a alta troposfera (baixa estratosfera) sobre a região de estudo, associado à diminuição (aumento) da intensidade do jato polar. Na primavera, a atividade de onda foi mais intensa e verificou-se uma mudança na direção do fluxo EPIS quando comparado com os EIT de inverno. O fluxo EPIS e as anomalias intra-sazonais do vento zonal foram mais fracos no verão. As anomalias intra-sazonais da circulação atmosférica e da atividade de onda na troposfera e estratosfera foram observadas por cerca de 10 dias antes da observação dos EIT de inverno. Portanto, a atividade intra-sazonal nos extratrópicos e as interações troposfera-estratosfera são fatores relevantes para um melhor entendimento da variabilidade da temperatura sobre a Península Antártica.The Antarctic climate plays a significant role for the global energy budget. Previous studies suggest that interactions tropics-extratropics and the dynamics of the stratosphere are important factors to understand climate variations in the extratropics. The air temperature near surface responds to changes in circulation in low and upper levels. However, no previous studies have objectively investigated the importance of intraseasonal variations in modulating temperature around the Antarctica Peninsula. The present study examines intraseasonal extreme anomalies of near surface air temperature in the Antarctica Peninsula, and investigates interactions tropics-extratropics and troposphere-stratosphere. Daily temperature data from stations located east and west of the Antarctica Peninsula during 1986-2002 are investigated. Spectral analyses indicate that intraseasonal anomalies in temperature records are statistically significant during summer, winter and spring in all stations. Based on these results, temperatures are band-filtered on intraseasonal timescales (20-100 days) and extreme anomalies are investigated in each season (spring, summer and winter) based on the quartiles of the distributions. Intraseasonal extreme temperature (IET) anomalies are more intense during winter than during summer. Variations in the atmospheric circulation during IET are investigated by performing composites of intraseasonal anomalies of the geopotential height in 200hPa, zonal wind in 200hPa and meridional wind in 850hPa. During the three seasons, cold IET are associated with persistent upper level cyclonic anomalies, easterly anomalies of the polar jet and cold advection in low levels over the Peninsula. Opposite features are observed during warm IET. An extratropical wave-train is observed during all IET with stronger intensity during winter and spring. This feature resembles the Pacific South American (PSA) teleconnection pattern. The Southern Hemisphere Annular mode during the IET, identified as the first Empirical Orthogonal Function (EOF) of the intraseasonal 700hPa geopotential height anomalies poleward of 20oS, is more intense (weak) during cold (warm) IET events during winter. The stratosphere-troposphere interaction during IET events was examined with composites of the Eliassen-Palm Flux intraseasonal anomalies (EPIS). During spring, the wave activity is more intense and the EPIS direction is opposite to winter. During summer, EPIS are weak. Intraseasonal anomalies in the circulation and the wave activity in the troposphere and stratosphere lead the IET during winter in about 10 days. Therefore, the intraseasonal activity in the extratropics and the interactions stratosphere-troposphere are important factors for a complete understanding of the temperature variability over the Antarctica Peninsula

Characterization and Spatial Coverage of Heat Waves in Subtropical Brazil

Given the increase in the frequency, intensity, and persistence of heat waves since the 1970s, and in view of the impacts that extreme temperatures may cause for society and the economy, this study aims to characterize heat waves in the subtropical region of Brazil and compare findings with the criterion defined by the World Meteorological Organization (WMO). Daily maximum temperature data was used. By using the percentile methodology, the subtropical region was divided into two regions: region 1 and region 2. We identified 54 heat waves in region 1 and 34 in region 2, which occurred more frequently in winter and spring, and less frequently in summer. A close relationship was observed between the Pacific Decadal Oscillation (PDO) and El Niño−Southern Oscillation (ENSO), both of which are able to modulate the heat waves in each of the different regions. Region 1 presented the highest number of heat waves during the warm (cold) phase of the PDO. As for ENSO, heat waves were more frequent in the neutral phase in both regions. Finally, there was shown to be an increase in the frequency and persistence of heat waves since the 1980s, especially in region 2. The methodology used in this study allows the identification and characterization of heat waves in several regions of different climates

Influence of the Antarctic Oscillation on the South Atlantic Convergence Zone

The South Atlantic convergence zone (SACZ) is the main summer-typical atmospheric phenomenon occurring in South America, and it is of great interest because it regulates the rainy season in the most populated regions of Brazil. Frequency variability, persistence, and geographical position of the SACZ and its relationship with intraseasonal variability is well described in the literature. However, the influence of extratropical forcing on the SACZ is not well understood. Consequently, the aim of this study is to evaluate the role of the Antarctic Oscillation (AAO) in SACZ events. The persistence and frequencies of SACZ events, mean, standard deviation of total precipitation per event, lag composite of daily precipitation and geopotential height anomalies were obtained for each phase of the AAO. Therefore, frequency, persistence and total precipitation of SACZ events were higher in positive AAO (AAO+) than negative AAO (AAO−). A teleconnection mechanism between the extratropics and the SACZ region is evident in AAO+, through intensification of the polar and subtropical jets, in the days preceding SACZ. The same was not observed in the AAO−, where the anomalies were confined in the subtropical region and displaced to the South Atlantic Ocean

UV solar radiation climatology and its behaviour during events of influence of the Antarctic ozone hole over south of Brazil

Ultraviolet solar radiation that reaches the surface of the Earth has a very important role in the energy budget of our planet, although at certain amounts of exposure it can be harmful not only for human health, but animals and plants. Brazil is a tropical country receiving high intensity of UV radiation mostly of the year. UV radiation, specially UV-B is mainly absorbed in the ozone layer, changes in ozone content or ozone distribution directly affects UV radiation attenuation, so that surface UV. Ozone hole is characterized by an intense ozone depletion in the stratosphere in Antarctic region, happening during spring in the south hemisphere. There is evidence of poor-ozone air masses detachment from polar vortex and reaching mid-latitude regions, such as South of Brazil. Those air masses cause impact on the regions which they act due to low ozone content, allowing more radiation to reach the surface. UV index data from a Brewer Spectrophotometer (MKIII #167), located in south of Brazil, in the Southern Space Observatory (29.42° S, 53.87° W) was analysed with data collected between 2005 and 2017. Ground data was compared to satellite-derived from OMI/Aura, resulting in a correlation coefficient of 0.95 %. The climatology of Brewer data was done, analysing seasonal and interannual variability. Wavelet analysis showed the influence of ENSO, QBO and solar cycle on the variability of UV index. The results show a typical seasonal behaviour of UV Index, reaching extreme during summer season. Events of secondary effects of Antarctic ozone hole, identified between 2005 and 2016 (Bittencourt, 2018), were selected and the behavior of UV index and UV-B non-weighted during those events were studied. All ten events studied showed a significant increase in UV radiation at the days of events, the majority resulted in an increase of 4 % of UV index for each 1 % ozone total column decrease. One specific event was described in detail due to the major ozone depletion. Occurred in October 2016, ozone depletion was of almost 20 % while UV index increased 88 % in relation to the climatological mean, raising the concern with public health regarding excess exposure to UV radiation

Brazilian Annual Precipitation Analysis Simulated by the Brazilian Atmospheric Global Model

The strategy for assessing simulations produced by climate models established as part of the Atmospheric Model Intercomparison Project (AMIP) delivers an outline for model analysis, verification/validation, and intercomparison. Numerical models are continuously being developed to find the best representation for the amount and distribution of precipitation in Brazil to improve the country’s precipitation forecast. This article describes the key features of the Brazilian Global Atmospheric Model (BAM) (developed by the Center for Weather Forecasting and Climate Studies of the National Institute for Space Research (CPTEC/INPE)) and analyses of its performance for annual rainfall climate simulations. This study considered the representation of the annual precipitation in Brazil mainly during the rainy season in the central part of Brazil by the BAM. The model was run over the 1990 to 2015 period using spectral Eulerian model dynamics with a 70-horizontal resolution of approximately 1.0∘× 1.0∘ and 42 vertical sigma levels. The analysis was divided into two stages: the annual precipitation and the rainy season precipitation. Model precipitation analyses were performed using statistical methods, such as the mean and standard deviation, comparing modeled data with observed data from two datasets, data from the XAV (observed data from INMET, ANA, and DAEE), and the Climate Prediction Center (CPC). In general, the BAM model simulations reasonably replicated the configuration of the spatial distribution of precipitation in the Brazilian territory almost entirely, especially compared with the XAV. The accumulated precipitation in the southern region presented great variation, accumulating from 750 mm year−1 in the extreme south to 1750 mm year−1 in the north of this region. Average values of the BAM accumulated precipitation ranged from 1000 to 2000 mm year−1, within the expected average, compared to observed values of 750–1500 mm year−1 (CPC and XAV, correspondingly). Although there was an underestimation of the accumulated precipitation by the model, the model reasonably reproduced the precipitation during the rainy season. The performed assessment identified model aspects that need to be improved