Modulation of ENSO-related climate variations across the Southwest U.S. by the Pacific Decadal Oscillation

Pacific Ocean temperature variations clearly modulate seasonal temperature and precipitation anomalies across the southwest United States. Extrema in the ENSO cycle now form the principal basis for seasonal climate predictions in the Southwest, with most predictive skill demonstrated for winter and spring months. More recently decade-scale variations associated with off-equatorial Pacific surface temperature anomalies have also been shown to be correlated with Southwest U.S. precipitation anomalies. Our study examines the joint probabilities of monthly and seasonal precipitation anomalies across the Southwest associated with ENSO and the Pacific Decadal Oscillation (PDO). We find that interannual predictive relationships between ENSO and Southwest climate anomalies are stronger during the positive phase of the PDO, when midlatitude north Pacific surface temperatures are colder than normal.