Future Changes in Winter Stationary Wave in East Asia and the North Pacific

Tuesday, 16 December 2014
Shunya Wakamatsu, Masashi Harada, Shoji Hirahara, Hirokazu Murai, Yoshinori Oikawa and Shuhei Maeda, Japan Meteorological Agency, Tokyo, Japan
Future changes in winter stationary waves and their possible mechanisms are investigated using Coupled Model Intercomparison Project Phase 5 (CMIP5: Taylor et al. 2012) models and a linear baroclinic model (LBM: Watanabe and Kimoto 2000, 2001). The CMIP5 multi-model ensemble showed a teleconnection pattern of stationary waves from East Asia to the North Pacific and a weakening of horizontal divergence over the Maritime Continent in the upper troposphere. To investigate dynamical relationships among these changes, we performed LBM experiments using the zonal mean basic state and zonally asymmetric thermal forcing. The pattern of differences between the future and present experiments was similar to the changes that had been 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 pattern, whereas the change in thermal forcing accounted for the eastward shift of the stationary wave. The results of storm track experiments conducted with the LBM to investigate the role of transient eddy feedback on stationary wave changes suggested that eddy feedback shifts the thermally forced stationary waves northward. This shift may explain the difference between the LBM experimental results and the CMIP5 future projection.