The linkage between the Pacific-North American teleconnection pattern and the North Atlantic Oscillation

In this study, using the ECMWF reanalysis data, the possible linkage between the Pacific-North American teleconnection pattern (PNA) and the North Atlantic Oscillation (NAO) during boreal winter (December- February) is investigated. The PNA and the NAO pattern are obtained by performing Rotated Empirical Orthogonal Function (REOF) analysis on an anomalous daily mean 300-hPa geopotential height field. The composite daily NAO indices show that the NAO indices are prone to be negative (positive) when the contemporary PNA indices are extremely positive (negative). The correlation coefficients between the daily PNA and NAO indices also confirm that, indeed, there is a significant anti-correlation between the PNA and NAO indices. The correlation peaks at a lag of 0 days (meaning contemporary correlation), and its value is 0.202. Analyses of a newly defined Rossby wave breaking index and diagnostics of the stream function tendency equation indicate that the anti-correlation between PNA and NAO may be caused by the anomalous Rossby wave breaking events associated with the PNA pattern. © 2009 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag GmbH.