Origin and propagation of planetary waves

Contact: Hauke Schmidt, Elisa Manzini, Felix Bunzel, Andreas Miller

During Northern hemispheric winter, stationary atmospheric waves originating from the surface can propagate up into the stratosphere. These waves, which are also referred to as planetary waves (PWs), reflect nothing more than the vertical transport of eddy heat and horizontal transport of momentum, the so-called Eliassen-Palm (EP) flux. Their dissipation in the stratosphere and, thus, the divergence of the EP flux, impacts the strength of the polar vortex and leads to a deceleration of the polar night jet.
As the summer troposphere is not transparent to PWs, their propagation is suppressed in the summer hemisphere. The relatively small amount of land masses in the Southern hemisphere compared to the Northern hemisphere, makes the wave activity generally weaker there. Here, the largest PW amplitudes are found in late winter and spring, when the strong polar vortex vanishes.

The figures above show the EP flux (arrows) as well as its divergence (contours), averaged over the winter (DJF, left) and summer (JJA, right) of the climatological year of a 50-year ECHAM6 simulation under stationary boundary conditions, representing the present-day (1990) climate state. The strongest deceleration of the polar night jet by EP fluxes occurs in Northern hemispheric winter.