Interannual Variability of the Rainy Season and Rainfall in the Brazilian Amazon Basin

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Abstract
Interannual variability of seasonal rainfall in the Brazilian Amazon basin is examined in context of its relationship to sea surface temperatures in the tropical Pacific and Atlantic Oceans. Linear correlations reveal strong relationships, but rainfall patterns are of regional scale. Areas of rainfall exhibiting strong relationships with SST are confined to the equatorial region of the Brazilian Amazon. The best relationships are found either during the season of transition between wet and dry regimes, or entirely within the dry season. It is hypothesized, and results are shown in support, that during the transition seasons, an important contributor to the SST control on seasonal totals is its influence on the timing on the rainy season onset or end. That influence appears to be stronger than the SST influence on the rainy season rain rate. Abstract Interannual variability of seasonal rainfall in the Brazilian Amazon basin is examined in context of its relationship to sea surface temperatures in the tropical Pacific and Atlantic Oceans. Linear correlations reveal strong relationships, but rainfall patterns are of regional scale. Areas of rainfall exhibiting strong relationships with SST are confined to the equatorial region of the Brazilian Amazon. The best relationships are found either during the season of transition between wet and dry regimes, or entirely within the dry season. It is hypothesized, and results are shown in support, that during the transition seasons, an important contributor to the SST control on seasonal totals is its influence on the timing on the rainy season onset or end. That influence appears to be stronger than the SST influence on the rainy season rain rate.