| Summary: | On Rio Grande do Sul the seasons of the year are well defined being felt, in its peculiar characteristics, in the winter,in the spring, in the summer and in the autumn. The pluviometric regime is quite regular and the precipitations are welldistributed during all the year on the State. The Multivariate Enso Index (MEI) lacks of a study about its relations withthe precipitation. It is a numeric index that integrates the action of different factors that characterize the phenomenon andthat oscilate between positive values for the warm phase, the El Niño, and negative values for the cold phase, the La Niña.It considers, in its composition, the following variables: sea level pressure, zonal and meridional wind components at thesurface, the Sea Surface Temperature (SST), the air temperature at the surface and a cloudiness indicator. This work hadthe objective to study the relations between the MEI and the SST of the Niño regions with the precipitations on Rio Grandedo Sul State. For this, it were utilized total monthly data of precipitation from 40 meteorological stations of Rio Grande doSul, bimonthly data of MEI and SST of the Niño regions for the period 1950 to 2002. The correlation coefficients betweenthe precipitation of the Rio Grande Do Sul with the MEI and the regions of the Niños showed low values due to the factof if using only the months of the beginning and end of the event. The MEI, although to be a more complex index of themethodologic point of view, it does not improve the coefficients of correlation with the precipitation of the State of the RioGrande do Sul, and it always presents lesser or equal values to obtained when using the TSM of the regions of the Niñosin the out/nov and nov/dez coupled of months. The MEI and the Niños regions 3 and 3.4 present the highest correlationcoefficient with the Rio Grande do Sul State precipitation for the bimonths oct/nov and nov/dec.
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