Effects of ENSO on precipitation in Mexico City

This study investigates the relationship between the phenomenon known as El Niño-Southern Oscillation, characterized by the ENSO Multivariate Index, and the annual precipitation around Mexico City. The spatial and temporal behavior of precipitation during the 1950-2010 period was also assessed, revealing that during the period mentioned the annual mean precipitation does not show a linear trend, but a variation with a single cycle only. Contingency tables and the Chi-square test were used to reject the hypothesis of independence between precipitation and ENSO. In addition, the bootstrap resampling technique showed that negative ENSO phases reduce precipitation in the Mexico City area; the neutral phase increases precipitation and lowers the probability that precipitation be below the median value. During the positive phase, precipitation is not significantly affected.