Frequency dependence of the structure and temporal development of wintertime tropospheric fluctuations comparison of a GCM simulation with observations

The datasets examined include NMC analyses of the 500 mb height and sea level pressure fields for 18 winters, as well as a 12-winter simulation of the same fields by a 15-wavenumber general circulation model at GFDL. Statistically significant phase differences between 500 mb height fluctuations at selected centers of action and the corresponding fluctuations at all other grid points are displayed for various frequency bands using a vectorial format. Similar plots are constructed to elucidate the vertical phase structure in the middle and lower troposphere at individual grid points, as well as the propagation characteristics of the sea level pressure field in the vicinity of sloping terrain. It is demonstrated that these phase/coherence diagrams offer a useful alternative for quantifying the lead/lag relationships between different anomaly centers associated with some of the well-known teleconnection patterns. Comparison between model and observational results indicates that the GCM examined here is capable of reproducing the frequency and geographical dependence of the principal modes of variability in the Northern Hemisphere wintertime circulation. -from Authors