Sea surface temperature (SST) anomalies caused by a warm core eddy (WCE) in the Southwestern Atlantic Ocean (SWA) rendered a crucial influence on modifying the marine atmospheric boundary layer (MABL). During the first cruise to support the Antarctic Modeling and Observation System (ATMOS) project, a WCE that was shed from the Brazil Current was sampled. Apart from traditional meteorological measurements, we used the Eddy Covariance method to directly measure the ocean–atmosphere sensible heat, latent heat, momentum, and carbon dioxide (CO2) fluxes. The mechanisms of pressure adjustment and vertical mixing that can make the MABL unstable were both identified. The WCE also acted to increase the surface winds and heat fluxes from the ocean to the atmosphere. Oceanic regions at middle and high latitudes are expected to absorb atmospheric CO2, and are thereby considered as sinks, due to their cold waters. Instead, the presence of this WCE in midlatitudes, surrounded by predominantly cold waters, caused the ocean to locally act as a CO2 source. The contribution to the atmosphere was estimated as 0.3 ± 0.04 mmol m−2 day−1, averaged over the sampling period. The CO2 transfer velocity coefficient (K) was determined using a quadratic fit and showed an adequate representation of ocean–atmosphere fluxes. The ocean–atmosphere CO2, momentum, and heat fluxes were each closely correlated with the SST. The increase of SST inside the WCE clearly resulted in larger magnitudes of all of the ocean–atmosphere fluxes studied here. This study adds to our understanding of how oceanic mesoscale structures, such as this WCE, affect the overlying atmosphere.

O presente estudo avalia o modelo WRF-Hydro uma ferramenta de previsão acoplada chuva/solo/vazão, buscando aperfeiçoar o grau de agilidade e confiabilidade das previsões na região considerada de grande vulnerabilidade, a bacia hidrográfica do Taquari-Antas/RS, localizada na região Sul do Brasil. A avaliação consistiu em analisar os resultados e a previsibilidade do modelo com diferentes resoluções espaciais na simulação de evento extremo ocorrido em janeiro de 2010. A primeira simulação foi realizada com duas grades do modelo meteorológico com 50 e 10 km e com a rede de canais com resolução de 1000 m. E a outra com três grades de 25, 5 e 1 km para meteorologia e rede de canais com 250 m. Avaliadas usando comparações da magnitude e da variabilidade dos fluxos da superfície da bacia, como precipitação e vazão do modelo com dados observados. Os resultados seguem as observações locais e apresentam bons resultados para servir como ferramenta em sistemas de alerta contra cheias nesta e em outras regiões. Predictability of the Wrf-Hydro Model in Hydrometeorological Modeling with Different Resolutions in the Taquari-Antas Basin A B S T R A C TThe present study evaluates the WRF-Hydro model, a rainfall/soil/flow coupled forecasting tool, aiming to improve the agility and reliability of the predictions in the region considered to be of great vulnerability, the Taquari-Antas/RS basin located in the region South of Brazil. The evaluation consisted of analyzing the results and predictability of the model with different spatial resolutions in the extreme event simulation that occurred in January 2010. The first simulation was performed with two grids of the 50 and 10 km meteorological model and with the channel network with resolution of 1000 m. And the other with three grids of 25, 5 and 1 km for meteorology and network of channels with 250 m. Evaluated using comparisons of magnitude and variability of basin surface fluxes, such as precipitation and flow of the model with observed data. The results follow local observations and present good results to serve as a tool in flood warning systems in this and other regions.Keywords: numerical forecasting, extreme events, WRF-Hydro, hydrological basin monitoring and hydro-meteorological modeling.

1 LMQA/CEPSRM/UFRGS -Porto Alegre -Rio Grande do Sul -2 GMO/CPTEC/INPE -São José dos Campos -São Paulo 3 gabriel.munchow@ufrgs.br RESUMO A camada limite planetária (CLP), região da atmosfera na qual habitamos, é fortemente regida pela interação com a superfície terrestre. Neste trabalho foi estudado o efeito na CLP da confluência Brasil-Malvinas utilizando o COAWST, um modelo numérico acoplado oceano-atmosfera-ondas-transporte de sedimentos. Para isso foi realizado dois experimentos, um somente com o modelo COAWST e outro somente o modelo atmosférico WRF. Foi notada uma intensificação nos gradientes horizontais de vento e theta, e no cisalhamento vertical do vento. Estas alterações podem levar a instabilidades afetando níveis mais altos da atmosfera. ABSTRACTThe planetary boundary layer (PBL) region of the atmosphere, is strongly influencied by the interaction with the surface. This paper studied the effect on PBL over the ocean using a coupled ocean-atmosphere-wave-sediment transport numerical model (COAWST). It was done two experiments, one with COAWST and another with atmospheric model WRF. INTRODUÇÃOA camada limite planetária (CLP), região da atmosfera na qual habitamos, é fortemente regida pela interação com a superfície terrestre (Stull, 2009). É nesta que ocorrem as trocas de energia entre a atmosfera e a superfície, formado por solo, vegetação, oceano, prédios, etc. Para cada caso, há interações e efeitos diferentes na atmosfera. Segundo Pezzi (2005), a CBM. Foram verificados gradientes horizontais e verticais de theta mais intensos, assim como cisalhamento do vento. Estas alterações podem levar a instabilidades ou outras alterações na atmosfera, mostrando a importância de estudos específicos sobre esta região utilizando modelo acoplado oceano-atmosfera.

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The state of Santa Catarina is often hit by extreme events such as heavy rain, windstorms, hail and eventually tornadoes. Thus, the goal of the present study was to verify how the inclusion of a larger number of observations could improve the prediction of such events. Thus, through a campaign carried out in the west of Santa Catarina, surface and radiosonde data were collected and assimilated through the GSI system. This process produced an updated initial condition to the weather prediction model WRF. The surface data assimilation had 84 new pressure observations. The radiosonde experiment had 162 observations of temperature, wind, and humidity assimilated. It was observed that the improvement of the initial condition through the insertion of the local surface and upper air data obtained during the campaign significantly improved the forecast in the conduced experiments.