Distribuição espacial da pluviometria em Alagoas com ênfase à variabilidade causada pelos padrões de temperatura da superfície do mar

Abstract

The characteristics of the spatial distribution of annual and intraannual rainfall in Alagoas were analyzed using observed data. The influence of relief in precipitation annual was assessed. Also, Pearson's Coefficient of Asymmetry was employed to determination areas of homogeneous rainfall. The emphasis of this work was on the influence of the sea surface temperature (SST) patterns associated with EI Niño and La Niña events and Atlantic Ocean Dipole SST pattern, both positive and negative phase, on rainfall variability. Rain annual and monthly mean series were selected from extinct SUDENE ( Superintendence for the Development of the Northeast) raingage network, with variable periods between 1931 – 1991. The evaluation of the influence of the anomalous SSt on the variability of rainfall was performed transforming the annual values into índices of Rainfall Deviations (RDI) from the mean normalized by the standard deviation and submetting them to a statical procedure nemed composed acses analyses. The results showed that there is a strong rain gradient (480 mm/100 Km) between the Coast and Interior. The configuration of the relief in Alagoas presented a close relationship with the distribution of the rainfall annual means. The intranual rainfall distribution (January to December) is very similar for the microregions within the rainy period April to July and the dry period October to January. The rainfall interannual variability was remarkable in all mesoregions, presenting below the normaltendency precipitation in mosto f years. There were identified six groups of área homogeneous rainfall in Alagoas. RDI were negative in most El Niño years of the composite (66,6%), with deviations between -2,5%. In La Niña events, the analysis showed a rainfall tendency above the annual mean in 53,3% of the composite, withdeviations between 4,8% and 46,5%. As far as the influence of the Atlantic Dipole positive phase SST patterns, the results showed a rainfall tendency to be below the annual mean in 70,0% of the cases of the composite, with deviations between -2,5% and -24,4%. The negative phase of the SST Dipole, on the other hand, the results presented a tendency for the rainfall to be above the annual mean in 72,7% of the cases of the composite, with deviations between 4,8% and 46,5%. The Atlantic SSt patterns seem to exert a major influence on Alagoas rainfall.