Variabilidade da Corrente do Brasil na região da Confluência Brasil-Malvinas através de simulações numéricas

Gramcianinov, Carolina Barnez

doi:10.11606/d.21.2013.tde-26092013-163638

Cited by 2 publications

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“…seasons. The southward shift of the BMC has been reported during the last decade in studies using observational and satellite data (e.g., Lumpkin and Garzoli, 2011;Goni et al, 2011), in numerical simulations (e.g., Gramcianinov, 2013;Combes and Matano, 2014) and also in future projections (e.g., Grieger et al, 2014;Pontes et al, 2016). However, the drift of the South Atlantic SST gradient does not explain completely the observed changes in genesis and track density in the South Atlantic, as also found by Reboita et al (2018).…”

Section: Intensity and Other Aspectsmentioning

confidence: 82%

Changes in South Atlantic Cyclones due Climate Change

Gramcianinov¹

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Cyclones distribution and intensities impact directly on human activities, mainly due to their associated intense precipitation and winds. The main aim of this thesis is to understand changes in the cyclones originated in the South Atlantic focusing on their genesis and intensifying mechanisms. Cyclones are identified and tracked based on the relative vorticity field at 850 hPa computed from the winds. The characteristics of the cyclones are obtained by diagnostic variables sampled within a radial distance from each cyclone center and to produce a spatial distribution of the cyclone properties at the time of genesis. Also, cyclone centered composites are used to analyze the cyclone structure and the evolution of cyclones during their genesis. The climatology of cyclones was done using NCEP-CFSR and shows four main cyclogenesis regions in the South Atlantic Ocean: on the Southern Brazilian coast (SE-BR, 30 • S), over the continent near the La Plata river discharge region (LA PLATA, 35 • S), on the southeastern coast of Argentina (ARG, 40 • S-55 • S) and on the Southeastern Atlantic (SE-SAO, centered at 55 • S and 10 • W). To access changes in cyclone development, we used the CMIP5 HadGEM2-ES historical experiment (1980-2005) and RCP8.5 future projection (2074-2099). The HadGEM2-ES can represent the main South Atlantic characteristics of cyclones according to NCEP-CFSR climatology. However, there is an underestimation in cyclone frequency in the equatorward side of the storm track, particularly in the LA PLATA region. The HadGEM2-ES RCP8.5 future projection shows a general decrease of approximately 10% of cyclogenesis in the South Atlantic domain, which is mainly related to the poleward shift of the storm track. However, LA PLATA region presents a slight increase in its cyclogenetic activity (6.1 and 3.6%, in the summer and winter, respectively). The increase in genesis at 30 • S over the continent is associated with the strengthening of the upper-level jet and the increase of warm and moisture advections at the same location. The enhance in the moisture transport from the tropics is also related to the intensification of the cyclone in the domain, mainly northward of 35 • S. Finally, a downscaling using WRF was performed in an attempt to improve the climate model resolution. However the downscaling produces less and weaker cyclones in the NCEP-CFSR and HadGEM2-ES runs. The only region that presented an improvement was LA PLATA, due to the better representation of local features related to orography and moisture processes. The downscaled HadGEM2-ES RCP8.5 also shows an increase in cyclogenesis in the LA PLATA region and other locations. The HadGEM2-ES RCP8.5 projection and its downscaling shows that the cyclogenesis in some locations of South America is increasing, mainly due to the increase in the low-level moisture content and the strengthening of the equatorward flank of the upper-level jet. The cyclones in this locations will be slightly intense (between 20 • S and 30 • S) and will affect a narrow area close to...

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Section: Intensity and Other Aspectsmentioning

confidence: 82%

Changes in South Atlantic Cyclones due Climate Change

Gramcianinov¹

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“…A redução do fluxo indicado como recirculação pode estar relacionado a uma migração para sul de toda a estrutura de recirculação. Uma provável indicação deste deslocamento seria a variabilidade encontrada na confluência Brasil-Malvinas e na frente da CB, que apresenta deslocamento para sul, constatado por dados observacionais (e.g Lumpkin & Garzoli, 2011;Goni et al, 2011) e inclusive em um trabalho envolvendo o mesmo modelo numérico utilizado (Gramcianinov, 2012).…”

Section: Considerações Finaisunclassified

Variabilidade de longo-termo do transporte da Corrente do Brasil ao longo de 30º S - Um estudo numérico

Carvalho¹

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Long term variability has been detected in the South Hemisphere large-scale wind pattern, using models, reanalysis and observations. Recent studies have suggested an oceanic response to changes in the atmospheric pattern, such as the Subtropical Front migration, increase in the Agulhas leakage and intensification of the subtropical gyre (SG). Despite the importance of the South Atlantic in the global heat distribution, the variability of its circulation and response to changes in the large-scale wind field remains unclear. The current study aims to investigate, from a numerical simulation using HYCOM (Hybrid Coordinate Ocean Model), the variability of the Brazilian Current (BC) volume transport at its central region (~30ºS) according to the wind field from Reanalysis I-NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research). The NCEP/NCAR results show an intensification and a poleward shift of the Southern Hemisphere westerly winds, leading changes in the wind curl along the SA, and a southern migration of the zero and maximum curl lines in subtropical latitudes. Even with the intensification of the mean wind curl over the SA, the time series of integrated Sverdrup return flow transport at 30ºS show a decrease between 1960 and 2010. This pattern is in agreement with the reduction trend in the zonal mean curl along the same latitude. The computed BC transport by HYCOM results present a similar trend to the integrated Sverdup transport (approximately 0.1 Sv per decade), with a 0.6 maximum correlation with a 2 year delay. Along the 30ºS, close to the western boundary, a north flow was identified as the return of a recirculation cell, with a 4,25±2,87 Sv mean transport. This flow also presents a reduction trend, which could be related to southern migration of the entire recirculation structure, following the Brazil-Malvinas confluence and Subtropical Front displacement. The residual transport at the western boundary (BC+Recirculation) shows an increase in the south flow that could indicates an increase of the SG, which is in agreement with the intensification and expansion of the Subtropical Ridge observed in the Reanalysis I. However, no significant correlation between the wind field and residual transport variability along the western boundary was found.

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Variabilidade da Corrente do Brasil na região da Confluência Brasil-Malvinas através de simulações numéricas

Cited by 2 publications

References 27 publications

Changes in South Atlantic Cyclones due Climate Change

Changes in South Atlantic Cyclones due Climate Change

Variabilidade de longo-termo do transporte da Corrente do Brasil ao longo de 30º S - Um estudo numérico

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