climate, weather, and weird weather
Dec. 29th, 2022 09:20 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
ljgeoffBecause the arctic has been warming, and warming faster than the mid-latitudes, the temperature difference between the arctic and the mid-latitudes is getting smaller.
A smaller temperature difference between the arctic and the mid-latitudes causes the polar jet stream to weaken.
Rossby waves flow across the mid-latitudes, flowing from west to east in a wavy pattern. So imagine a wave that flows north from southern California, up the Rockys, until it hits the northern jet stream up by the arctic circle, bounces off the jet stream, and bends to the south.
When the jet stream is weakened and that rossby wave hits it, the rossby wave actually distorts the jet stream. When the jet stream is weak and distorted, it's unable to keep the polar vortex trapped over the arctic. Instead of a tight, cyclonic wind over the pole, the polar vortex gets sloppy and starts spinning outside of its zone, dipping down onto the mid-latitudes.
click to animate (how cool is that!) (from Uniquorn on the Arctic Ice Blog)
Sometimes the rossby waves crash into the jet stream like waves crashing onto a breakwall, and are pushed up on top of the polar vortex. This action is called a sudden stratospheric warming. Imagine that air that got picked up in southern California crashing into and over the jet stream, piling on top of the polar vortex like a baker's torch on a Baked Alaska, squishing the polar vortex all over the mid-latitudes.
Because it's so high up in the atmosphere, the effects of sudden stratospheric warming takes a while to reach the surface, but mainly what you see is weird weather - unusually cold temps in the south and warmer than average temps in the arctic. The cold snap of February 2021 that took out the Texas power grid and killed as many as 700 people across the US was caused by a sudden stratospheric warming formed on January 5th, about 5-6 weeks before the cold outbreak.
Interesting, huh? Can you visualize it now?
A smaller temperature difference between the arctic and the mid-latitudes causes the polar jet stream to weaken.
Rossby waves flow across the mid-latitudes, flowing from west to east in a wavy pattern. So imagine a wave that flows north from southern California, up the Rockys, until it hits the northern jet stream up by the arctic circle, bounces off the jet stream, and bends to the south.
When the jet stream is weakened and that rossby wave hits it, the rossby wave actually distorts the jet stream. When the jet stream is weak and distorted, it's unable to keep the polar vortex trapped over the arctic. Instead of a tight, cyclonic wind over the pole, the polar vortex gets sloppy and starts spinning outside of its zone, dipping down onto the mid-latitudes.
click to animate (how cool is that!) (from Uniquorn on the Arctic Ice Blog)
Sometimes the rossby waves crash into the jet stream like waves crashing onto a breakwall, and are pushed up on top of the polar vortex. This action is called a sudden stratospheric warming. Imagine that air that got picked up in southern California crashing into and over the jet stream, piling on top of the polar vortex like a baker's torch on a Baked Alaska, squishing the polar vortex all over the mid-latitudes.
Because it's so high up in the atmosphere, the effects of sudden stratospheric warming takes a while to reach the surface, but mainly what you see is weird weather - unusually cold temps in the south and warmer than average temps in the arctic. The cold snap of February 2021 that took out the Texas power grid and killed as many as 700 people across the US was caused by a sudden stratospheric warming formed on January 5th, about 5-6 weeks before the cold outbreak.
Interesting, huh? Can you visualize it now?