THE INFLUENCE OF STRONG EL NINO PHASES ON THE RAINFALL OVER THE YUCATAN PENINSULA, MEXICO

The combination of several large-scale atmospheric influences makes the complex climatology of the Yucatán Peninsula difficult to predict. This study explores the most important physical modulator of the rainfall over México, the El Niño Southern Oscillation (ENSO), and its effects over the peninsula. Two different analyses were applied: non-parametric correlations between the Standardized Anomaly Indices of the long-term seasonal precipitation and the Multivariate ENSO Index; and the assessment of the rainfall response to three case studies, a relatively long hot ENSO phase (1957-58), and the strongest Niños of the twentieth century (1982-1983 and 1997-1998). The main factor determining the ENSO influence over the Yucatan Peninsula precipitation was its intensity: the strong Niños of 1982-83 and 1997-1998 had a positive effect on the rainfall, particularly during the dry-season when conditions were generally wetter than normal over the entire region; furthermore, an unusually wet Nov-Apr period within an intense El Niño phase, provides a reliable indication that rainfall is likely to surpass long-term means for the wet season (May-Oct) as well.