Determination of Homogeneous Precipitation Regions of the Standardized Precipitation Index (SPI) in the Eastern Amazon

Abstract This paper aims to determine homogeneous regions of the SPI-6 in the Eastern Amazon and analyze the main characteristics of dry and rainy events in each region. For the calculation of the SPI, we used rainfall data of 72 rainfall stations distributed in the eastern Amazon. Furthermore, were used Ward hierarchical grouping to identify homogeneous regions and the Principal Components Factor Analysis (PCA) to determine the main climate variability patterns associated with dry and rainy events. The results showed three homogeneous regions (HR): HR-1 (coast), HR-2 (central region) and HR-3 (south). Generally, the coastal region showed more dry events than rain. In the other regions (central and south) the situation is reversed, i.e, there are more rain events, but with short duration. The results obtained by PCA showed that the dry and wet events in Eastern Amazonia were associated, mainly, to climate variability associated the Atlantic Ocean (Atlantic Dipole) and Pacific Ocean (ENSO).



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