Reconstruction of the winter Pacific-North American teleconnection pattern during 1895-1947 and its application in climatological studies

Abstract

The Pacific-North American (PNA) teleconnection pattern is one of the most prominent teleconnection patterns in the Northern Hemisphere winter It manifests as anomalies in the 700 or 500 rnb geopotential height field and is closely related to the upper-level flow patterns and surface temperature and precipitation conditions in the United States. Various indices were developed to represent the strength of the PNA teleconnection. However, their apphcation in climatological research CLIMATE RESEARCH Clim. Res. is limited by a short record length as continuous upper-level measurements are widely available only since 1947. The purpose of this study is to reconstruct the winter PNA pattern for the period 1895 to 1947. A regression model is developed based on the relationship between the PNA pattern, represented by a PNA index, and surface temperature anomaly f~eld across the continental United States. The model can explain over 89 % of the variance in the PNA Index and offers unbiased estimates. Using this model, the winter PNA index is extended back to the 1895-96 winter. Analysis of winter precipitation anomalies in the United States from 1895 to 1988 illustrates the application potential of this extended record. With a longer record length, more extreme cases of the PNA teleconnection can be identified to analyze its relation to surface conditions. The extended PNA index is useful in explaining the cooling trend from the 1940s to the 1970s in the eastern United States. It is also significantly related to an extended Southern Oscillation index from 1895 to 1988. However, the relationship is not strong enough to suggest a completely synchronized occurrence of the 2 teleconnection patterns.