Principal components of the North American summer temperature field and the antecedent oceanic and atmospheric conditions

The North American summer temperature field is evaluated in terms of the preceding patterns of the ocean and atmosphere. It is found that the planetary scale circulation associated with the thermal field over the western tropical Pacific and the ocean-atmosphere interaction over the central North Pacific-Aleutian region are important in determining the summer surface temperature pattern over North America. Also, evidence is presented for the possible impact of the El Nino-Southern Oscillation on the summer circulation pattern. It is suggested that by using the principal components, the predictability of regional circulation can be evaluated as a linear combination of independent sources of variability.