El Niño and its effect on precipitation in Arizona and Western New Mexico

Abstract

Abstract This paper focuses primarily on the effect of El Niño on seasonal and annual precipitation at 26 locations in Arizona and western New Mexico for an 86‐year period from 1900 to 1985. Following Rasmusson (1984), each year is classified as either a non‐El Niño year (51) or an El Niño year (35), with the El Niños designated as being very weak (4), weak (8), moderate (12), or strong (11). Using the Mann‐Whitney U‐test for the 19 stations in Arizona, we find that, in the spring (March‐May) and in the autumn (September‐November), there is a positive relationship between precipitation in Arizona and both moderate and strong El Niños. These results are verified by correlating seasonal and annual precipitation for the complete 26‐station network with the pressure difference between Tahiti and Darwin. Plausible physical explanations for these results are given.