Impacts of Slowed Tropical Circulation on Winter Stationary Waves in East Asia and the North Pacific

Future changes in winter stationary waves are investigated using Coupled Model Intercomparison Project Phase 5 (CMIP5) models and a linear baroclinic model (LBM). The CMIP5 models showed a wave-like pattern of stationary waves from East Asia to the North Pacific and a weakening of horizontal divergence over the Maritime Continent. To investigate dynamical relationships among these changes, we performed LBM experiments using the zonal mean basic state and zonally asymmetric thermal forcing. The differences between the future and present experiments were similar to the changes projected by the CMIP5 models, although positions and amplitudes differed slightly. In addition, two of the LBM experiments showed that the change in the basic state explained most of the changes in the stationary wave, whereas the change in thermal forcing accounted for the eastward shift of the stationary wave. The storm track experiments conducted with the LBM to investigate the role of transient eddy feedback on stationary wave changes suggested that the feedback shifts the thermally forced stationary waves northeastward. This shift may explain the difference between the LBM experiments and the CMIP5 future projection.