On the influences of the El Niño, La Niña and Atlantic Dipole pattern over Amazonian Rainfall During 1960-1998

This work analyzes the influence of the large scale modes of the climate variability dominant in the tropical Pacific and Atlantic on the Amazonian rainfall. Composite analyses of the precipitation anomalies are based on the years of the occurrences of El Niño (La Niña) and the sea surface temperature (SST) anomalous north/south dipole pattern in the tropical Atlantic of the last four decades (1960 to 1998). The anomalous precipitation composites for the years of extremes in the Southern Oscillation (El Nino or La Nina) as well as for the years with north/south SST dipole in the Atlantic, in the Amazon during the austral summer and autumn present values (magnitude and sign) consistent with previous studies. However, during those years with the simultaneous occurrences of El Nino and negative SST anomalies in the tropical South Atlantic and positive SST anomalies in the tropical North Atlantic, the negative precipitation anomalies intensify over eastern and central Amazon suggesting that the SST dipole pattern in the tropical Atlantic plays an important role in the Amazon rainfall distribution.

Key-words: Legal Amazonian, ENSO, seasonal precipitation, climatic variability.