Winter cold of eastern continental boundaries induced by warm ocean waters
In winter, northeastern North America and northeastern Asia are both colder than other regions at similar latitudes. This has been attributed to the effects of stationary weather systems set by elevated terrain (orography), and to a lack of maritime influences from the prevailing westerly winds. However, the differences in extent and orography between the two continents suggest that further mechanisms are involved. Here we show that this anomalous winter cold can result in part from westward radiation of large-scale atmospheric waves—nearly stationary Rossby waves—generated by heating of the atmosphere over warm ocean waters. We demonstrate this mechanism using simulations with an idealized general circulation model, with which we show that the extent of the cold region is controlled by properties of Rossby waves, such as their group velocity and its dependence on the planetary rotation rate. Our results show that warm ocean waters contribute to the contrast in mid-latitude winter temperatures between eastern and western continental boundaries not only by warming western boundaries, but also by cooling eastern boundaries.
© 2011 Macmillan Publishers Limited. Received 30 August 2010, accepted 10 February 2011, Published online 30 March 2011. We thank D. Abbot, I. Eisenman, X. Levine and T. Merlis for comments. This research was supported by the National Oceanic and Atmospheric Administration Climate and Global Change Postdoctoral Fellowship administered by the University Corporation for Atmospheric Research (Y.K.), by a David and Lucile Packard Fellowship (T.S.), and by a grant from the National Science Foundation (AGS-1019211). The simulations were performed on the California Institute of Technology's Division of Geological and Planetary Sciences Dell cluster. Author Contributions: Y.K. and T.S. designed the study and wrote the paper; Y.K. performed the numerical simulations and data analyses.
Supplemental Material - nature09924-s1.pdf