Influence of Zonal Mean Flow Change on Stationary Wave Fluctuations

Abstract

The fluctuation of stationary waves caused by zonal mean flow changes is investigated using a barotropic model and GCM simulated upper-level data. The EOF analysis of monthly mean ? fluctuations during winter shows that a positive anomaly at the jet stream accompanies a negative anomaly of zonal mean flow in the high latitudes. The typical magnitudes of the anomalous zonal mean flow are 5 and 8 m s?1 in the jet stream latitudes and in the high latitudes, respectively. With these fluctuations of the basic state, the wave propagation characteristics are significantly modified from month to month. The zonal mean flow changes subject to fixed large-scale mountains result in a large part of the stationary wave fluctuations. It is also demonstrated that the precise location of the turning latitude plays an important role in the pattern of stationary wave responses to a fixed forcing.