How will climate change affect planetary waves?

Question

You can see planetary/rossby waves in the meanders of the jet stream. In short: If an air parcel moves from warm subtropics towards the pole, it will deviate toward the east due to conservation of angular momentum (movement towards the equator will lead to deviation toward the west). That results in a meandering motion.

How will climate change affect planetary wave activity and zonal wavenumber? Does polar amplification reduce planetary activity because of a smaller temperature gradient between subtropics and polar region? Will cooling of the stratosphere influence planetary waves as well?

Answer 1

As a non-climate specialist, this topic is on the edge of my understanding of meteorology, but here are some papers that I found potentially relevant to your topic.

Here is a quote from the summary of Limpasuvan and Hartmann, 1999:

The planetary wave propagation characteristics can be used to link changes in the tropospheric annular mode to changes in the strength of the stratospheric polar vortex during winter. Planetary waves are strongly attracted to polar regions during the low phase of the annular mode when the tropospheric westerlies are displaced equatorward. We should expect a weaker stratospheric polar vortex then, since planetary waves weaken the polar vortex by generating irreversible mixing.

And here is a quote from Shepherd and McLandress, 2011

In particular, the tropospheric warming that is robustly expected from climate change leads to a strengthening of the upper flanks of the subtropical jets, which causes the critical layers on the equatorward side of the jets to move upward, and with them the Rossby wave drag, allowing more Rossby wave activity to penetrate into the subtropical lower stratosphere (Figs. 4, 5). Because the subtropics represent the critical region for wave driving of the Brewer–Dobson circulation, the circulation is thereby strengthened.

So my conclusion from these two papers (there is obviously a lot more detail in the full text) is that polar vortex will weaken, subtropical jets and Brewer-Dobson circulation will strengthen, and Rossby waves will penetrate farther south. Of note, neither paper seemed (to me) to indicate that a cooler stratosphere was predicted.