• JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
 
  Bookmark and Share
 
 
Doctoral Thesis
DOI
10.11606/T.21.2006.tde-24092009-140739
Document
Author
Full name
Leandro Calado
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2006
Supervisor
Committee
Silveira, Ilson Carlos Almeida da (President)
Castro Filho, Belmiro Mendes de
Fontes, Roberto Fioravanti Carelli
Lorenzzetti, Joao Antonio
Pereira, Adriene Ferreira
Title in Portuguese
Dinâmica da interação da atividade de meso-escala da Corrente do Brasil com o fenômeno da ressurgência costeira ao largo de Cabo Frio e Cabo de São Tomé, RJ
Keywords in Portuguese
corrente do Brasil
meandros
modelos de feição
vórtices
Abstract in Portuguese
Os meandros da Corrente do Brasil ao largo do sudeste brasileiro s~ao singulares em termos de sua composic¸ ~ao termohalina. Estes v´ ortices, principalmente na regi~ao de Cabo Frio e Cabo de S~ao Tom´e, constituem um sistema integrado a ressurg^encia costeira e a pr´opria Corrente do Brasil, caracterizando um sistema din^amico que propomos denominar Corrente do Brasil-v ´ ortice-ressurg^encia. Apresentamos uma metodologia de construc¸ ~ao de modelos param´etricos das feic¸ ~oes oceanogr´aficas (ou Modelos de Feic¸ ~ao) que comp~oem o sistema. Estes modelos s~ao capazes de construir tridimensionalmente feic¸ ~oes oceanogr´aficas individuais a partir de dados sin´oticos de superf´?cie e fundo para elaborac¸ ~ao de campos iniciais de modelos num´ericos, com o objetivo de compreender a interac¸ ~ao do sistema din^amico Corrente do Brasil-v´ ortice-ressurg^encia. Atrav´es da simulac¸ ~ao num´erica dos campos iniciais baseados nos Modelos de Feic¸ ~ao investigamos o processo que conduz `a assimetria termohalina dos v´ ortices da Corrente do Brasil, acima descrita. Esta foi devida a aproximac¸ ~ao desses v´ ortices junto ao talude continental e ao ajustamento barocl´?nico das correntes `as menores profundidades. Verificamos, ainda, que a penetrac¸a~o da A´ gua Central do Atla^ntico Sul pela camada de Ekman de fundo n~ao tem efeito significativo na estrutura dos v´ ortices. Realizamos experimentosnum´ericos adicionais com o objetivo de investigar quais os tipos de instabilidade geof´?sica estariam envolvidas no fen^omeno do crescimento dos meandros e v´ ortices da Corrente do Brasil. Analisando os resultados atrav´es de c´alculos de convers~ao de energia pudemos concluir que o sistema Corrente do Brasil-v´ ortice-ressurg^encia apresenta instabilidade mista ( barotr ´opica e barocl´?nica). Contudo, verificamos quantitativamente que a instabilidade barocl´?nica foi dominante. O sistema, no entanto, mostrou-se sens´?vel `a ac¸ ~ao da tens~ao de cisalhamento do vento de nordeste na regi~ao e consequentemente `a ressurg^encia costeira. Interpretamos tal sensibilidade como fator respons´avel pela relev^ancia da instabilidade barotr ´opica no processo de crescimento dos meandros da Corrente do Brasil. Por fim, verificamos que um meandro cicl ^onico frontal, quase-estacion´ario, em condic¸ ~oes especiais de crescimento por mecanismo de instabilidade, pode auxiliar no estabelecimento da ressurg^encia costeira. O v´ ortice do Cabo de S~ao Tom´e simulado apresenta velocidade de fase muito baixa e cresce em direc¸ ~ao a oceano aberto, de forma praticamente perpendicular `a quebra de plataforma. Logo, o crescimento do vo´ rtice de Cabo de Sa~o Tome´ faz com que o mesmo advecte A´ gua Costeira para seu interior provocando, por continuidade, afloramento da A´ gua central do Atla^ntico Sul junto `a costa. Assim, podemos dizer que h´a, de fato, uma interac¸ ~ao entre o sistema costeiro e a atividade de meso-escala da Corrente do Brasil.
Title in English
Dynamics of meso-scale interactions activity between Brazil Current and coastal upwelling phenomenon off Cape Frio and Cape of São Tomé, RJ
Keywords in English
Brazil Current
Feature Models.
South Atlantic
Western Boundary Currents
Abstract in English
The Brazil Current meanders off the Brazilian southeast coast are unique in terms of their thermohaline structure. These eddies, especially off the Cape Frio and S~ao Tom´e region constitute an integrated system with the Brazil Current and the coastal upwelling, characterizing a dynamic system which we propose to nominate as Brazil Current-eddy-upwelling system. We present a methodology of parametric model construction of the oceanographic features (or Feature Models) which compose the inferred system . These models are capable of three-dimensionally building independent the relevant features from synoptic surface and bottom data in order to compose the initial fields for numerical models with the objective of understanding the dynamics of the interaction of Brazil Current-eddy-upwelling system. By means of numerical simulation usingthe initial fields based on the Feature Models, we investigated the process which conducts to the thermohaline asymmetry of the eddies in the Brazil Current as mentioned above. This is due to the baroclinic approximation of the currents to shallower depths. The penetration of the Central Water in the South Atlantic by the bottom Ekman layer does not have a significant effect on the eddy structure. Additional numerical experiments were carried out with the objective of unders tanding which of the geophysical instabilities were involved in the growth of the Brazil Current meanders and eddies. The results analyzed through calculation of energy conversion allowed us to conclude that the Brazil Current-eddie-upwelling system presents mixed instability (barotropic and baroclinic). However, the baroclinic instability is dominant and is mostly associated to the vertical shear of the oceanic currents. The system, however,was sensitive to the action of the northeast wind shear and consequently to the coastal upwelling. Such sensibility was interpreted as the main responsible for the relevance of barotropic instability in the growth process of meanders in the Brazil Current. Lastly, we verified that a quasi-stationary frontal cyclonic meander, in special growth conditions by instability mechanisms, mayhelp in establishing coastal upwelling. The simulated S~ao Tom´e Cape Eddy presented a very low phase velocity and grew towards the open sea, almost perpendicularly to the continental shelf break. Therefore, the growth of the S~ao Tom´e Cape Eddy advects Coastal Water into its center and, therefore, lead to upwelling of South Atlantic Central Water near the coast. We can therefore say that there are in fact interaction mechanisms between the coastal system and the meso-scale activity of the Brazil Current.
 
WARNING - Viewing this document is conditioned on your acceptance of the following terms of use:
This document is only for private use for research and teaching activities. Reproduction for commercial use is forbidden. This rights cover the whole data about this document as well as its contents. Any uses or copies of this document in whole or in part must include the author's name.
TESE_LEANDRO.PDF (20.25 Mbytes)
Publishing Date
2010-12-13
 
WARNING: Learn what derived works are clicking here.
All rights of the thesis/dissertation are from the authors
Centro de Informática de São Carlos
Digital Library of Theses and Dissertations of USP. Copyright © 2001-2021. All rights reserved.