Variability and factors of influence of extremewet and dry events in Northern Mexico

The goal of this study was to generate a method to examine seasonal variability by climatic classification and Pacific seasonal factors to identify extreme wet and dry events in northern Mexico for the period 1952-2013. Using the standardized precipitation and evapotranspiration index (SPEI) on scales of three months (SPEI-3) and 24 months (SPEI-24), the variability of extreme wet and dry events were measured. The SPEI-3 and SPEI-24 anomalies were divided by the standard deviation (standardized Z anomalies). A Pearson correlation for SPEI-3, SPEI-24, Pacific decadal oscillation (PDO) and the oceanic El Niño index (ONI) was applied. Wet extreme events were recorded in 1954, 1968, 1976-1977, 1981, 1984, 1986 and 2003, of which the greatest magnitude was recorded in 1984 for the Sinaloa-very dry region. Extreme dry events were recorded in 1952-1953, 1990, 1997, 2003 and 2011-2013. The Z anomalies of the wet extreme events observed coincide with +PDO phase anomalies. In this study, the El Niño southern oscillation (ENSO) has little influence on wet and dry extreme events in northern Mexico. The negative phase anomalies of sea surface temperature (-SST) in the equatorial and eastern Pacific are indicators of extreme wet events. This study shows for the first time the influence of the PDO and the ONI on seasonal variability of extreme wet and dry events by climatic classification through the SPEI index in northern Mexico.