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Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

Abstracts

The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

Dynamic Topography; Geoid Models; Geostrophic Currents


A utilização de modelos geoidais na determinação da Topografia Dinâmica Média foi impulsionada com o lançamento dos satélites do sistema GRACE, já que seus modelos apresentam precisão e resolução espacial e temporal sem precedentes. No presente trabalho, além do modelo de nível médio do mar DNSC08, foram utilizados os seguintes modelos geoidais com o objetivo de calcular as TDMs: EGM96, EIGEN-5C e EGM2008. No método adotado, foram calculadas as respectivas correntes geostróficas para o Atlântico Sul a partir das TDMs. O grau e ordem dos modelos geoidais influenciam diretamente na determinação da TDM e correntes. Neste trabalho verificou-se que presença de ruídos da TDM requer a utilização de técnicas de filtragem eficientes, como o filtro baseado em Singular Spectrum Analysis, que apresenta vantagens significativas em relação aos filtros convencionais. As correntes geostróficas resultantes dos modelos geoidais foram comparadas com resultados de modelo numérico hidrodinâmico HYCOM. Como principais conclusões, os resultados mostraram que as TDMs e respectivas correntes geostróficas calculadas com os modelos EIGEN-5C e EGM2008 foram similares aos resultados do modelo numérico, especialmente em relação às principais feições de grande escala, como as correntes do contorno e a retroflexão na Confluência Brasil Malvinas.

Topografia Dinâmica; Modelos Geoidais; Correntes Geostróficas


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Publication Dates

  • Publication in this collection
    15 May 2012
  • Date of issue
    Mar 2012

History

  • Received
    19 Feb 2011
  • Accepted
    02 Mar 2012
  • Reviewed
    16 Aug 2011
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