Thirty-one years of monthly data are used to evaluate the seasonal dependence of the associations between large-scale temperature anomalies over the United States and the North Pacific Ocean. Both station (grid-point) values and empirical orthogonal functions of temperature are used in the correlative analysis.
The North Pacific sea surface temperature (SST) anomalies correlate most highly with temperature fluctuations over the southeastern and the far western states. Correlations with the SST anomalies have opposite signs in the two portions of the United States. The associations with the SST anomalies are independent of season only in the western states. The association involving the southeastern states is strongest during the winter and insignificant during the summer. The pattern of North Pacific SST that correlates most highly with the United States temperature is an east-west SST gradient between the West Coast and 35°N, 160°W. Statistically significant fractions of temperature variance over at least some areas of the United States are described by regression onto the SST anomalies in all seasons except spring. The results imply some seasonal predictability based on North Pacific SST patterns alone, although useful predictability appears to be confined primarily to the winter.
The pattern analysis shows that the failure to rotate the dominant eigenvectors can obscure the spatial and temporal interrelationships deduced from the two sets of data fields.