Influence of the Pacific Decadal Oscillation on Arizona Winter Precipitation during Years of Neutral ENSO

Abstract

Abstract Recent studies indicate that correlations between ENSO and winter precipitation in the southwestern United States may vary with the phase of the Pacific decadal oscillation (PDO). In-phase relationships between ENSO and the PDO strengthen the impact of ENSO on winter precipitation, while out-of-phase relationships weaken this impact. It has been suggested that this knowledge of PDO phase can improve long lead winter forecasts. However, all of these studies have focused on the impact of the PDO on both El Nino and La Nina only. Years of neutral ENSO have been neglected even though neutral years occur roughly half the time and coincide with highly variable winter precipitation. It is expected that some of this variability may be caused by the phase of the PDO, although the extent of its relationship with ENSO is not well understood. When years of neutral ENSO from 1925 to 1998 are split by PDO phase, it is found that Arizona winter precipitation and its predictability are strongly influenced. Years...