A Rotated Eigenanalysis of the Correlation between 700 mb Heights and Sea Surface Temperatures in the Pacific and Atlantic'

Abstract

Associations between Pacific and Atlantic sea surface temperature (SST) and the 700 mb circulation were studied using 30 years (1949-78) of gridded monthly data. The monthly data were grouped into four (nonstandard) seasons for the analysis. The linear correlation between the two fields (SST and 700 mb heights) was analyzed by finding the eigenvalue solution of the mean product matrix of the cross correlations. This technique, introduced by Prohaska, was modified through the use of a varimax rotation. The result is a set of pairs of patterns (one pattern for each medium) which explains part of the linear correlation between the two fields. The number of significant modes (pairs) was determined by a Monte Carlo simulation. One well-known atmospheric teleconnections pattern, referred to as the Pacific/North American (PNA) pattern by Wallace and Gutzler, was found in all seasons; however, seasonal differences were noted. During the warm season, the PNA pattern manifests itself as the Great Plains (GP) pattern. The OP pattern results in dry/hot (wet/cool) conditions over much of the central and eastern United States. Another, the Northeast (NE) pattern, has a center along the coast of the eastern United States and can result in dry/cool (wet/warm) weather in the Northeast. Additionally, the North Atlantic Oscillation was identified during both the coldand warm seasons. In the examination of lag associations, significant relationships in which the atmosphere leads the ocean were found for all seasons (and many modes) in the Pacific, but only for the case of January-March 700 mb heights leading SST (by one to two months) in the Atlantic. In the case of the ocean leading the atmosphere (by one to two months), significant results were found only for Pacific SST leading JanuaryMarch 100 mb heights.