Southern oscillation index (SOI) and total monthly rainfall relationship in Maringá, state of Paraná, Brazil

Abstract

The correlation between the southern oscillation index (SOI) and the deviation of total monthly rain for Maringá region (Lat.: 23º25´S; Long.: 51º57´ W and, Alt.: 542 meters) was analyzed in a series of 21 years (76-96). SOI shows inverse correlation (-0,14) with the rain deviation observed in the region. The correlation coefficient is significant when the SOI is related to the rain deviation of three months in advance, i.e., the SOI of January reflects the alteration of total rain of April and May, indicating a 3-to-4-month delay between an event of anomalous temperature and pression in the Pacific Ocean, and its manifestation in north/northwest of the state of Paraná. When El Niño has moderate to strong intensity (negative SOI) the rain deviation is positive during 47% of the months analyzed, indicating in this case that SOI values can be used for quantitative forecast of rain deviation, with a 3-to-4-month antecedence and, of course, 47% of probability.