I was under the impression that, as the poles are MORE affected by global warming, the jet stream is becoming weaker? is that incorrect?
...but I fully agree with the rest of your comment.
(Edit: though apparently the additional moisture in the Tropics more than counteracts any reduction in temperature difference: see link in Retric's comment)
The projected warming at the North Pole is much stronger than the projected warming at the equator, decreasing the temperature gradient. However the moisture carrying capacity of air increases exponentially with temperature. Since the equator starts warmer, a given change in temperature has a bigger effect on moisture carrying capacity. It turns out that heating up the equator by one degree Celsius and the North Pole by 2 degrees Celsius increases the moisture capacity gradient, despite the temperature gradient dropping. And that increasing moisture capacity gradient strengthens the jet stream.
(at least that's the intuitive reason they were probably going for. In reality there are many factors and a good bit of "if we simulate it this keeps happening")
But I also thought that it was the jet stream getting weaker that caused it to meander more (which sounds like it could increase CAT events ??), which we seem to be observing ??
The truth is there are many oscillations and teleconnections(themselves being impacted by global warming) which influences this temperature gradient on a local/seasonal basis. QBO, El Nino/La Nina and mountain torque events to name a few can move and shift heat at the tropopause in a short period of time and is why we see this wider variance at both ends of the spectrum.
https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/202...
The poles warm FASTER than the equator. Thus, the global temperature gradients are getting smaller.
And as a result, not only does the Jetstream weaken: as a result, weather patterns become more stable which leads to greater continuous periods of draught or flooding.
“The new study, by University of Chicago Professor Tiffany Shaw and NSF NCAR scientist Osamu Miyawaki, uses climate models to show that climate change intensifies this density contrast because moisture levels for air above the tropics will increase more than above the poles.”
https://news.ucar.edu/132935/jet-stream-winds-will-accelerat....
That weakening means the jetstream meanders more, with more latitudinal movement in its form.
The strength overall of the jetstream wind is weaker when it's meandering, but can also be much more intense in places.
This says nothing about humidity or energy or pressure, just windspeed and direction.
“The new study, by University of Chicago Professor Tiffany Shaw and NSF NCAR scientist Osamu Miyawaki, uses climate models to show that climate change intensifies this density contrast because moisture levels for air above the tropics will increase more than above the poles.”
https://news.ucar.edu/132935/jet-stream-winds-will-accelerat....
The article cites the Prosser Report which contradicts this claim, but I find it hard to understand how this could be true for very long. Why wouldn't the atmosphere stabilize as gradients diminish?