Search

Nesse estudo utiliza-se simulações numéricas do modelo ECHAM5/MPI-OM para identificar os padrões dominantes de energia cinética com o objetivo de explicar a gênese e manutenção das trajetórias preferenciais dos ciclones extratropicais (Storm Tracks, ST) no Hemisfério Sul, localizando suas origens e apresentando suas trajetórias preferenciais através do vetor E ⃗. Os resultados mostraram que para um cenário futuro, os ST parecem estar ligados diretamente ao fluxo de oeste, podendo-se afirmar que em um cenário futuro haverá uma intensificação desse transporte e os mesmos poderão deslocar-se mais para Sul. Dessa forma, espera-se que haja implicações nos abastecimentos de água de algumas regiões como o Sul da África, onde maior parte da população é dependente da precipitação na região. No Sul do Brasil, os resultados indicam aumentos nas chuvas durante os meses de verão, contrastando com uma diminuição na frequência dos ST e aumento na intensidade no inverno. Sugerimos que essas mudanças podem impactar a dinâmica climática do litoral sul brasileiro, com magnitude ainda desconhecida.

Based on coupled climate experiments conducted with the coupled ICTP-CGCM model focusing on interglacial stages MIS5e (127 ka), MIS11c (409 ka) and MIS31 (1,072 ka), the Austral summer monsoonal system is investigated. The interannual variability and intensity of monsoon events are analysed from vorticity indices and air-sea interaction processes for Africa, Australia and South America monsoons. Results demonstrated with respect to present day conditions, an orbital driven decrease in precipitation in summer, but slightly shift of the onset and demise periods of monsoons. Sensitivity experiments indicate, furthermore, that the monsoons are forced not only by external factors such as the dominant effect of insolation, but also by distant climate anomalies, such as surface temperature of the equatorial Atlantic and Pacific basins. During the interglacial stages, cooling occurs in the Southern Hemisphere whereas Northern Hemisphere substantially warms, inducing remarkable changes in the position of the oceanic subtropical high pressure systems and equatorial convergence zone. Regionally, these mechanisms contribute to periods of drought, with reduced precipitation rate over sectors of the Amazon and Northeastern Brazil, northern Australia and southern Africa. Monsoonal rainfall shows different responses to precessional forcing, as well as the relationship between the monsoon and Niño 3.4 differs among the interglacial stages. Compared to current climate, correlation analyses have demonstrated weaker influence of the equatorial Pacific Ocean on the Austral summer monsoon for the MIS5e, MIS11c and MIS31. Exception is noticed for the South America monsoon, where the Niño 3.4 exerts a more prominent role in these distant intervals, in consonance with the tropical Atlantic in particular during the MIS5e.

The Southern Brazilian Continental Shelf (SBCS) is an area with great ecological and economic importance to Brazil. In this region can be observed the recurrent passage of frontal systems and extra-tropical cyclones, which are more frequent during the winter months of the southern hemisphere. These systems act on the ocean surface layers as direct driving forces, which may change the thermohaline structure of the water column and induce sea level perturbations. This study used the coupled ocean-atmosphere regional model (COAWST) to evaluate the effect of the passage of a frontal system associated with an extra-tropical cyclone. The ROMS oceanic model was configured with two nested grids, in order to solve the hydrodynamic processes at different scales. The parent (20–40° S/40–60° W) and child (25–29.3° S/46.3–50° W) grid comprise the coastal region, with a horizontal resolution of 1/9° and 1/27°, respectively, with 32 vertical levels. The initial conditions are the Global Analysis Forecast from CMEMS and forcing files used the Climate Forecast System v.2 (CFSv2) data, from NCEP. This event took place on the continental shelf of the State of Santa Catarina, in September of 2016. The model results were compared to remote sensing data and to the tide gauges from the City of Imbituba (State of Santa Catarina, Brazil). The comparison showed a correlation higher than 78 % between sea level rise data and the model results. The filtering of sea level data made it possible to identify the meteorological component in the model results. The comparison between the tidal-gauge and the model output presented values under 25 cm. The model was capable of representing the sea level anomalies propagation associated with the passage of the atmospheric frontal system. The model output showed the presence of a sea level anomaly propagating northward along the continental shelf at 480 km day−1, probably associated with the presence of a coastal-trapped wave.

An adequate representation by models and reanalyzes is fundamental since the coverage by observational data on the oceans is still limited. Therefore, this paper aims to evaluate the influence of the wind near the surface on the heat fluxes during the southern winter and summer seasons. Datasets from Coupled Model Intercomparison Project Phase 5 (CMIP5) and reanalyzes were used, in comparison to Objectively Analyzed Air - sea Fluxes (OAFlux) for the South Atlantic Ocean (SAO) during 1980-2005. Results point out an overestimation on the CMIP5 models and reanalyzes to reproduce the heat flux latent and sensible fluxes of SAO, mainly at medium and high latitudes. One possibility may be related the underestimating of surface wind speed, causing an impacts on the heat exchange between ocean and atmosphere. It was also possible to verify that the representation of heat flux, specific humidity, and air and ocean temperatures shows small biases (Mean Bias Error (MBE) to specific humidity (±5 kg.kg-1) and sensible heat flux (±10 W.m-2)). To the test Root Mean Square Error (RMSE)-observations Standard deviation Ratio (RSR), air temperature values are less than 1 °C, and for the wind with values greater than 2 m.s-1. There is less precision of CMIP5 models than OAFlux, resulting in low correlation values (between -0.3 and 0.3). On the other hand, the reanalyzes show small biases in air and ocean temperatures (between ±1 °C) and significant correlations (above 0.9) with the best performances for the NCEP and ERA5.

Here we investigate the ocean-atmosphere coupling and the contribution of the Sea Surface Temperature (SST) variations in: 1) Brazil-Malvinas Confluence (BMC) region, 2) Southwest Atlantic Ocean and 3) Southern Brazil. Numerical simulations of the ECHAM5/MPI-OM coupled ocean-atmosphere model were used to analyze the changes in the seasonal trajectory of the extratropical cyclones, in terms of intensification of physical mechanisms and implications for future scenarios. The numerical experiment for the future scenario considered an atmospheric CO2 concentration of approximately 770 ppm, which represents an increment of more than 350 ppm over the current values recorded by the Mauna Loa reference station. For this scenario, the results indicated a Storm Tracks (ST) displacement of 5° latitude toward south and changes of the meridional transport of sensible heat, close to 50°S. The increase in SST induces ST intensification and consequently an increase in the occurrence of extratropical cyclones. Overall, in the BMC region, we found a change in the pattern of cyclogenetic activity occurrence, with less frequent, but more intense events. On the Southern Brazilian region, the results of this study indicate increases in rainfall during summer months, whereas, a decrease in frequency and an increase in intensity were found for wintertime. We suggest that these changes could impact the climate dynamic of the Brazilian South coast, with a magnitude yet unknown.

DOI: não consta, por isso foi disponibilizado o link de acesso. Marine Isotope Stage 31 (MIS31, between 1085 and 1055 ka) was characterized by higher extratropical air temperatures and a substantial recession of polar glaciers compared to today. Paleoreconstructions and model simulations have increased the understanding of the MIS31 interval, but questions remain regarding the role of the Atlantic and Pacific oceans in modifying the climate associated with the variations in Earth's orbital parameters. Multi-century coupled climate simulations, with the astronomical configuration of the MIS31 and modified West Antarctic Ice Sheet (WAIS) topography, show an increase in the thermohaline flux and northward oceanic heat transport (OHT) in the Pacific Ocean. These oceanic changes are driven by anomalous atmospheric circulation and increased surface salinity in concert with a stronger meridional overturning circulation (MOC). The intensified northward OHT is responsible for up to 85 % of the global OHT anomalies and contributes to the overall reduction in sea ice in the Northern Hemisphere (NH) due to Earth's astronomical configuration. The relative contributions of the Atlantic Ocean to global OHT and MOC anomalies are minor compared to those of the Pacific. However, sea ice changes are remarkable, highlighted by decreased (increased) cover in the Ross (Weddell) Sea but widespread reductions in sea ice across the NH.

A atmosfera consiste em um dos menores reservatórios de água do planeta, contribuindo com 0,001% da massa total da água presente, porém, sendo de fundamental importância para os processos físicos na atmosfera. A partir de dados obtidos através de 130 perfis de radiossondas realizados durante dez cruzeiros oceanográficos nos meses de outubro e novembro, entre 2004 e 2015, analisa-se a influência dos gradientes de temperatura da superfície do mar (TSM) e a passagem de sistemas atmosféricos transientes na variabilidade espaço-temporal da concentração de vapor d’água da camada limite atmosférica marinha (CLAM), sobre a região da Confluência Brasil Malvinas (CBM), enfatizando-se a Operação Antártica 31 (OP31). Os dados de vapor d’água são obtidos calculando-se umidade específica em superfície e água precipitável dentro da camada limite atmosférica. Os resultados mostram que os gradientes térmicos entre as águas quentes da Corrente do Brasil (CB) e as águas frias da Corrente das Malvinas (CM) produzem diferenças significativas no conteúdo de vapor d'água da CLAM nos dois lados da frente oceanográfica. Na superfície, o valor médio da umidade específica sobre o lado quente (frio) foi 8,4 ± 1,67 mm (7,08 ± 1,51 mm). A CLAM foi localmente modulada pela TSM, sendo cerca de 2g/kg mais úmida sobre a região quente da frente oceanográfica em relação à região fria. Em todas as observações realizadas, o vapor d’água integrado na CLAM foi diretamente influenciada pela passagem de sistemas atmosféricos transiente.

Anomalies of sea surface temperature (SST) favor the emergence of climatic variability modes, which can be transferred by atmospheric teleconnections to different regions of the globe. The present study sought to identify influences of the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO) on the air temperature in Brazil, during the period from 1901 to 2012. It was found that the negative periods of the PDO and AMO (1901-2012) have a greater influence on the South and North regions of Brazil. When these modes of variability are in opposite phases (1901-1927), they mainly interfere in the southern region of Brazil. On the other hand, when the PDO is in the negative phase and the AMO is moving from the positive to the negative phase (1944-1975), the northern region of Brazil is more influenced.

It has long been recognized that the amplitude of the seasonal cycle can substantially modify climate features in distinct timescales. This study evaluates the impact of the enhanced seasonality characteristic of the Marine Isotope Stage 31 (MIS31) on the El Niño–Southern Oscillation (ENSO). Based upon coupled climate simulations driven by present-day (CTR) and MIS31 boundary conditions, we demonstrate that the CTR simulation shows a significant concentration of power in the 3–7-year band and on the multidecadal timescale between 15 and 30 years. However, the MIS31 simulation shows drastically modified temporal variability of the ENSO, with stronger power spectrum at interannual timescales but the absence of decadal periodicity. Increased meridional gradient of sea surface temperature (SST) and wind stress in the Northern Hemisphere subtropics are revealed to be the primary candidates responsible for changes in the equatorial variability. The oceanic response to the MIS31 ENSO extends to the extratropics, and fits nicely with SST anomalies delivered by paleoreconstructions. The implementation of the MIS31 conditions results in a distinct global monsoon system and its link to the ENSO in respect to current conditions. In particular, the Indian monsoon intensified but no correlation with ENSO is found in the MIS31 climate, diverging from conditions delivered by our current climate in which this monsoon is significantly correlated with the NIÑO34 index. This indicates that monsoonal precipitation for this interglacial is more closely connected to hemispherical features than to the tropical–extratropical climate interaction.

It has long recognized that the amplitude of the seasonal cycle can substantially modify climate features in distinct timescales. This study evaluates the impact of enhanced seasonality characteristic of the Marine Isotope Stage 31 (MIS31) on the El Niño-Southern Oscillation (ENSO). Based upon coupled climate simulations driven by present day (CTR) and MIS31 boundary conditions, we demonstrated that the CTR simulation shows signicant concentration of power in the 3–7 year band and on the multidecadal time scale between 15–30 years. However, the MIS31 simulation shows drastically modified temporal variability of the ENSO, with stronger power spectrum at interannual time scales but absence of the decadal periodicity. Increased meridional gradient of SST and wind stress in the Northern Hemisphere subtropics, in concert with weaker seasonal cycle of the windstress in the MIS31 simulation, revealed to be the primary candidates responsible for changes in the equatorial variability. The oceanic response to the MIS31 ENSO extends to the extratropics, and fits nicely with SST anomalies delivered by paleoreconstructions. The implementation of the MIS31 conditions results in distinct global monsoon system and its link to the ENSO in respect to current conditions. In particular, the Indian monsoon intensified but no correlation with ENSO is found in the MIS31 climate, diverging from conditions delivered by our current climate in which this monsoon is significatly correlated with the NINO34 index. This indicates that monsoonal precipitation for this interglacial is more closely connected to hemispherical features than to the tropical-extratropical climate interaction.

Este trabalho analisa a variação sazonal da temperatura do ar à superfície (Tar) na Antártica, e sua relação com os modos de variabilidade climática El Niño-Oscilação Sul (ENOS) e Oscilação Antártica (OA). Os resultados indicam que para os 4 períodos sazonais as Tar nas estações localizadas no setor oriental da Antártica apresentaram significativas correlações negativas (nível de significância de 1% na maioria das estações) com a OA. Todavia o único período sazonal, em que o setor continental (Amundsen-Scott, Dome C) apresentou forte correlação negativa com a OA, foi durante o inverno (significativa a 1%). Correlações positivas foram encontradas (significâncias entre 1% e 5%) entre as Tar da Península Antártica e Shetland do Sul com a OA para os períodos de outono, inverno e primavera. Os resultados demonstram a influência que a OA exerce sobre a climatologia da Tar na Antártica. É importante notar um dipolo entre as regiões oriental da Antártica e da Península Antártica, no que concerne as influências da OA. O modo de variabilidade ENOS apresentou correlação negativa significativa com as três estações da Península Antártica somente durante a primavera, enquanto que para a estação Rothera, à oeste da Península, a correlação foi significativa também para o outono e inverno. A correlação entre ENOS e Tar foi positiva e significativa no setor do Mar de Ross durante a primavera, e com o setor oriental da Antártica durante o verão, com nível de significância chegando a 5%. This study analyzes the seasonal variation in surface air temperature (Tar) in Antarctica, and its relationship with the modes of climate variability, namely El Niño-Southern Oscillation (ENSO) and Antarctic Oscillation (AO). The results indicate that during the 4 seasonal periods the Tar in the stations located in the eastern sector of Antarctica showed significant negative correlations (at 1% significance level on most stations) with AO. However, the only seasonal period in which the continental sector (Amundsen-Scott, Dome C), showed strong negative correlation with the AO was in winter (at 1%). Positive correlations were found (ranging from 1% to 5%) between the Tar values at the Antarctic Peninsula and South Shetland with AO for autumn, winter and spring. These results demonstrate the influence that AO exerts on the climatology of the Tar in Antarctica. It is important to note a dipole between eastern regions of Antarctica and the Antarctic Peninsula concerning the influences of AO. The ENSO mode presented significant negative correlation with the three stations at the Antarctic Peninsula only during the spring, while for the station Rothera, at the West sector the correlation was also significant for the autumn and winter. The correlation between ENSO and Tar was positive and significant in the Ross Sea sector during the spring, and with the eastern sector of Antarctica during the summer, with significance level reaching 5%.

Made available in DSpace on 2022-04-28T19:11:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) University of the Fraser Valley Extratropical cyclones and your preferred range of operation “storm tracks” play a key role in the global energy system, especially in regions of high latitudes. In this way, the current climatology of these systems are evaluated and its possible changes under situations of increased global temperature and CO2 concentrations are analysed from the global coupled climate model European Centre/Hamburg Model versão 5 / Max Planck Institute-Ocean Model (ECHAM-5-MPI-OM). So, with the intention of obtaining greater precision of intensity and spatial displacement of extratropical cyclones, evaluate important variables of climate energy component, as the flow of heat sensitive and dominant patterns of kinetic energy. To future conditions, the results obtained show that the trajectories of ST may suffer modifications in the distribution, moving South towards the pole. The results also indicate that variations in sea ice cover and sea surface temperature are fundamental in the distribution of the cyclonic activity in future climate conditions. Instituto Nacional de Pesquisas Espaciais Centro Regional Sul de Pesquisas Espaciais (CRS-INPE), Av. Roraima 1000, Bairro Camobi Universidade Federal do Rio Grande Instituto de Oceanografia, Av. Itália km 8 Universidade Federal de Viçosa Departamento de Engenharia Agrícola, P. H. Holfs S/N Universidade Estadual Paulista Faculdade de Ciências Centro de Meteorologia de Bauru, Av. Eng. Luiz Edmundo Carrijo Coube, 14-01 Universidade Estadual Paulista Faculdade de Ciências Centro de Meteorologia de Bauru, Av. Eng. Luiz Edmundo Carrijo Coube, 14-01

Based upon coupled climate simulations driven by present-day conditions and conditions resembling the Marine Isotope Stage 31 (this simulation is called WICE-EXP), insofar as the West Antarctic Ice Sheet (WAIS) configuration is concerned, it is demonstrated that changes in the WAIS orography lead to noticeable changes in the oceanic and atmospheric circulations. Compared with the present-day climate, WICE-EXP is characterized by warmer conditions in the Southern Hemisphere (SH) by up to 5°C in the polar oceans and up to 2°C in the Northern Hemisphere (NH). These changes feed back on the atmospheric circulation weakening (strengthening) the extratropical westerlies in the SH (northern Atlantic). Calculations of the southern annular mode (SAM) show that modification of the WAIS induces warmer conditions and a northward shift of the westerly flow; in particular, there is a clear weakening of the polar jet. These changes lead to modification of the rate of deep water formation, reducing the magnitude of the North Atlantic Deep Water but enhancing the Antarctic Bottom Water. By evaluating the density flux it is found that the thermal density flux has played a main role in the modification of the meridional overturning circulation. Moreover, the climate anomalies between the WICE-EXP and the present-day simulations resemble a bipolar seesaw pattern. These results are in good agreement with paleorecontructions in the framework of the Ocean Drilling Program and Antarctic Geological Drilling (ANDRILL) project.

Observacoes em superficie da temperatura global sobre os continentes e oceanos indicaram um aumento no ultimo seculo como resposta a eventos cadas vez mais frequentes e intensos de anomalia da temperatura da superficie do mar. Desta forma, o objetivo deste estudo e apresentar as influencias exercidas pela Oscilacao Multidecadal do Atlântico (AMO) sobre as temperaturas da America do Sul, durante o periodo de verao austral, para o periodo de 1901 a 2012. Foi observado que a temperatura do ar apresentou tendencias positivas estatisticamente significativas para a regiao Sudeste e Sul do Brasil. Padrao semelhante foi observado para os extremos de temperatura para todo o periodo em analise. Ao dividir em periodos conforme a oscilacao da AMO, e removendo a tendencia, verifica-se que as anomalias das temperaturas do ar sao mais acentuadas durante a AMO-, e esperado um aumento (reducao) da temperatura do ar e seus extremos principalmente sobre a Bacia do Rio da Prata e Nordeste do Brasil (Centro-Oeste e Sudeste do Brasil). Estes padroes sao esperados pelo fato que durante a AMO+ ocorre um aumento da nebulosidade sobre a regiao correspondente a formacao da ZCAS, alem de um deslocamento mais para norte da ZCIT, fazendo com que a temperatura do ar fique com menores valores. Por outro lado, no extremo Sul da AS, as anomalias negativas da Tar e Tmin durante a AMO+ estao associadas com o transporte de umidade do Oceano Atlântico Sul pelo centro de alta pressao que se forma no litoral da Argentina. Decadal fluctuations in South American air temperature during the southern summer period and its relationship to the North Atlantic Ocean A B S T R A C T Surface observations of global temperature on continents and oceans have indicated an increase in the last century in response to increasingly frequent and intense sea surface temperature anomaly events. Thus, the aim of this study is to present the influences exerted by the Atlantic Multidecadal Oscillation (AMO) on South American temperatures during the austral summer period, from 1901 to 2012. It was observed that the air temperature presented statistically significant positive trends for the Southeast and South of Brazil. Similar pattern was observed for temperature extremes for the entire period under analysis. By dividing into periods as the AMO fluctuates, and removing the trend, it is found that anomalies in air temperatures are more pronounced during AMO-, an increase (decrease) in air temperature and its extremes is expected mainly over the Silver River Basin and Northeast Brazil (Midwest and Southeast Brazil). These patterns are expected due to the fact that during AMO + there is an increase in cloudiness over the region corresponding to the formation of ZCAS, as well as a further northward displacement of the ZCIT, making the air temperature lower. On the other hand, in the extreme south of AS, negative Tar and Tmin anomalies during AMO + are associated with the transport of moisture from the South Atlantic Ocean through the high pressure center that forms off the Argentine coast. Keywords: AMO, air temperature and teleconnection

A atmosfera consiste em um dos menores reservatórios de água do planeta, contribuindo com 0,001% da massa total da água presente, porém, sendo de fundamental importância para os processos físicos na atmosfera. A partir de dados obtidos através de 130 perfis de radiossondas realizados durante dez cruzeiros oceanográficos nos meses de outubro e novembro, entre 2004 e 2015, analisa-se a influência dos gradientes de temperatura da superfície do mar (TSM) e a passagem de sistemas atmosféricos transientes na variabilidade espaço-temporal da concentração de vapor d’água da camada limite atmosférica marinha (CLAM), sobre a região da Confluência Brasil Malvinas (CBM), enfatizando-se a Operação Antártica 31 (OP31). Os dados de vapor d’água são obtidos calculando-se umidade específica em superfície e água precipitável dentro da camada limite atmosférica. Os resultados mostram que os gradientes térmicos entre as águas quentes da Corrente do Brasil (CB) e as águas frias da Corrente das Malvinas (CM) produzem diferenças significativas no conteúdo de vapor d'água da CLAM nos dois lados da frente oceanográfica. Na superfície, o valor médio da umidade específica sobre o lado quente (frio) foi 8,4 ± 1,67 mm (7,08 ± 1,51 mm). A CLAM foi localmente modulada pela TSM, sendo cerca de 2g/kg mais úmida sobre a região quente da frente oceanográfica em relação à região fria. Em todas as observações realizadas, o vapor d’água integrado na CLAM foi diretamente influenciada pela passagem de sistemas atmosféricos transiente. A B S T R A C TThe atmosphere is the smallest contributor of the planet's water tanks, providing only 0.001% of the water total mass, however, it is of fundamental importance for playing a key role in the atmosphere's physical processes. The data were obtained from 130 radiosondes profiles taken during ten oceanographic cruises carried out during the months of October and November between 2004 and 2015, analyzed the influence of the sea surface temperature (SST) gradients and the passage of transient atmospheric systems at the spatial-temporal variability of the water vapor concentration within the marine atmospheric boundary layer (MABL), over Brazil-Malvinas Confluence (BMC), emphasizing the Antarctic Operation 31 (AO31). Water vapor data are obtained by calculating surface specific moisture and precipitable water within the atmospheric boundary layer. The results show that the thermal gradients between the warm waters of Brazil Current and the cold waters of the Malvinas Current were able to produce significant differences in the water vapor content of the MABL on both sides of the oceanographic front. On the surface, the average of the specific humidity over the warm (cold) side was 8.4 ± 1.67 mm (7.08 ± 1.51 mm). The MABL was locally modulated by the SST, being about 2 g/kg wetter over the warm part of the front with respect to the cold one. In all the observations made, the water vapor integrated in the MABL was directly influenced by the passage of transient atmospheric systems.Key words: Southwest Atlantic; Oceanographic front; Transient atmospheric system

Brazil is responsible for 27% of the world production of soybeans and 7% of maize. Mato Grosso and Para states in Brazil are among the largest producer. The viability to the cultivation of maize (Zea mays) and soybeans (Glycine max), for future climate scenarios (2070-2100, GHG) is evaluated based on crop modeling (DSSAT) forced by observational data and regional climate simulations (HadRM3). The results demonstrated that a substantial reduction in the yield in particular for maize may be expected for the end of the 21st century. Distinct results are found for soybeans. By applying the A2 climate changes scenario, soybean yield rises by up top 60% assuming optimum soil treatment and no water stress. However, by analyzing the inter-annual variability of crop yields for both maize and soybean, could be demonstrated larger year-to-year fluctuations under greenhouse warming conditions as compared to current conditions, leading to very low productivity by the end of the 21st century. Therefore, these Brazilian states do not appear to be economically suitable for a future cultivation of maize and soybeans. Improved adaptation measures and soil management may however partially alleviate the negative climate change effect.