A curious and well known feature of Earth’s climate is that in winter, eastern continental boundaries in midlatitudes are considerably colder than western boundaries and even continental interiors at similar latitudes. A variety of factors play a role in generating this feature, among them orographic stationary waves in the atmosphere and the generally more maritime character of the climate on western coasts in the region of midlatitude westerly winds. One factor that had been previously unrecognized is that a localized heating such as over western boundary currents leads to upstream cooling (to the west) through the generation of stationary Rossby waves. These waves form a plume that advects cold polar air into the region upstream of the heating and that extends westward over a length scale that depends, among other factors, on Earth’s rotation rate. The animation on the left shows this cooling upstream of the warm localized heating region and how it depends on rotation rate. A curious aspect (explained by propagation properties of Rossby waves, see Kaspi and Schneider 2012) is that the cold region expands as the planetary rotation rate increases, although other wave scales generally decrease with increasing rotation rate.
Kaspi, Y., and T. Schneider, 2012: The role of stationary eddies in shaping midlatitude storm tracks J. Atmos. Sci., submitted.