Research Article Spatial and Temporal Variability of Rainfall in Eastern Amazon during the Rainy Season Douglas Batista da Silva Ferreira, 1,2 Everaldo Barreiros de Souza, 1 Bergson Cavalcanti de Moraes, 1 and Luiz Gylvan Meira Filho 1 1 Vale Institute of Technology, Boaventura da Silva Street 955, 66055-090 Bel´ em, PA, Brazil 2 Post-Graduate Program in Environmental Sciences, Federal University of Par´ a, Augusto Corrˆ ea Street 1, 66075-110 Bel´ em, PA, Brazil Correspondence should be addressed to Douglas Batista da Silva Ferreira; douglas.silva.ferreira@itv.org Received 12 November 2014; Revised 8 January 2015; Accepted 13 January 2015 Academic Editor: Hossein Tabari Copyright © 2015 Douglas Batista da Silva Ferreira et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Empirical orthogonal functions (EOF) and composites analysis were employed on pentad data in order to investigate the tropical atmospheric-ocean patterns over the Atlantic Ocean and the spatial-temporal characteristics of the rainfall in eastern Amazon during the peak of the rainy season (February to April). Te EOF results evidenced that the Intertropical Convergence Zone (ITCZ) is the main rainfall-producing system in eastern Amazon during the rainy season. Conditions associated with the southward SST gradient in the intertropical Atlantic formed the dynamic patterns that favored the position of the ITCZ to south of the equator, thus explaining the predominance of positive precipitation anomalies in eastern Amazon, especially in the state of Maranh˜ ao and northeastern Par´ a during the February and April months. 1. Introduction Te Amazon in South America and equatorial Africa and Indonesia form the three main centers of action of deep convection around the global tropical belt [1]. In particular, the Amazon exhibits a high spatial and temporal variability of rainfall with a very pronounced seasonality, such that the rainy and dry seasons typically occur during the months of summer/autumn and winter/spring, respectively [2]. Te focus of the present paper is on the spatial distribution of rainfall in eastern Amazon (see location in Figure 1(a)) during the period in which the maximum (the peak of the rainy season) of the annual cycle is reached, that is, February to April (FMA). Te climatological mean (1981– 2010) for FMA (Figure 1(a)) clearly shows that the continental precipitation maximum is concentrated over the eastern Amazon, with values above 11mm/day in most of the states of AP (Amap´ a), PA (Par´ a), and MA (Maranh˜ ao). Previous observational studies have investigated the cli- matological rainfall patterns in the Amazon [3] and reported that the pluviometric variability is explained by the man- ifestation of a wide range of meteorological systems, like the Intertropical Convergence Zone (ITCZ), squall lines, infuences of frontal systems, South Atlantic Convergence Zone (SACZ), and meso- and local-scale systems [4, 5]. On the other hand, the Amazonian climate variability is infuenced by the large-scale tropical climatic modes associated with the El Ni˜ no/Southern Oscillation (ENSO) cycle in the Pacifc Ocean [6, 7] and with the interhemispheric sea surface temperature (SST) gradient phases in the Atlantic Ocean [8, 9]. Of relevance to the scope of the present work is the Atlantic gradient that appears dominant during the austral autumn. Typically, a northward (southward) gradient features simultaneous positive/negative (negative/positive) SST anomalies in the tropical north/south basin of the Atlantic Ocean [8]. Such meridional gradients hydrostatically control the sea level pressure, wind patterns, and the moisture convergence in the lower-levels, thereby infuencing the lati- tudinal positioning of the ITCZ during its seasonal migration towards the south Atlantic [10]. Hindawi Publishing Corporation e Scientific World Journal Volume 2015, Article ID 209783, 9 pages http://dx.doi.org/10.1155/2015/209783