This study investigates the origin of the interdecadal variability in the warm Arctic and cold Eurasia (WACE) pattern, which is defined as the second empirical orthogonal function of surface air temperature (SAT) variability over the Eurasian continent in Northern Hemisphere winter, by analyzing the Twentieth Century Reanalysis dataset. While previous studies highlight recent enhancement of the WACE pattern, ascribing it to anthropogenic warming, the authors found that the WACE pattern has experienced a seemingly periodic interdecadal variation over the twentieth century. This long-term variation in the Eurasian SAT is attributable to the altered coupling between the Siberian high (SH) and intraseasonal Rossby wave emanating from the North Atlantic, as the local wave branch interacts with the SH and consequentially enhances the continental temperature perturbation. It is further identified that these atmospheric circulation changes in Eurasia are largely controlled by the decadal amplitude modulation of the climatological stationary waves over the North Atlantic region. The altered decadal mean condition of stationary wave components brings changes in local baroclinicity and storm track activity over the North Atlantic, which jointly change the intraseasonal Rossby wave generation and propagation characteristics as well. With simple stationary wave model experiments, the authors confirm how the altered mean flow condition in the North Atlantic acts as a source for the growth of the Rossby wave that leads to the change in the downstream WACE pattern.
Bibliographical noteFunding Information:
Acknowledgments. This research is supported by KMIPA2015-2093(PN17040) of the Korean government. M.-K. Sung is supported by the National Research Foundation of Korea grant (NRF-2016R1A6A3A11931456). Y.-S. Choi is supported by ‘‘Development of Climate and Atmospheric Environmental Applications’’ project, funded by ETRI, which is a subproject of the ‘‘Development of Geostationary Meteorological Satellite Ground Segment’’ (NMSC-2017-01) program funded by NMSC of KMA. Y.-S. Choi also acknowledges support by the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the National Aeronautics and Space Administration (NASA).
© 2018 American Meteorological Society.
- Atmospheric circulation
- Rossby waves
- Stationary waves