Abstract
The seasonal variations of convection associated with the South American monsoon system (SAMS) are analyzed using pentad means of outgoing longwave radiation (OLR) data during the 1979–2006 period. The data is filtered for the 0.4–1.2 year scale and an empirical orthogonal function (EOF) analysis is applied. The results provide three dominant modes with distinct convective features, which are referred to as: equatorially antisymmetric, intertropical convergence zone (ITCZ) and symmetric modes. The first two modes vary in an annual scale, and the latter one in a semiannual scale. The evolving aspects of these modes are studied by correlating (lagged and simultaneously) the principal component of each mode and the filtered OLR time series. The antisymmetric and the ITCZ modes evolve smoothly into each other reflecting the northwestward and northeastward propagation of convective activity. The propagation rates vary depending on development stage and region considered. On the other hand, the symmetric mode with the largest convective activity in the western Amazon evolves independently, and depicts the transition from dry to wet seasons and vice-versa.
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Acknowledgements
The authors were partially supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico of Brazil. This paper is part of the doctoral thesis of the first author. Thanks are due to two anonymous reviewers for their useful comments on earlier version of this work.
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Garcia, S.R., Kayano, M.T. Some evidence on the relationship between the South American monsoon and the Atlantic ITCZ. Theor Appl Climatol 99, 29–38 (2010). https://doi.org/10.1007/s00704-009-0107-z
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DOI: https://doi.org/10.1007/s00704-009-0107-z