BAN #295: Polar vortex meanderings, Cooper hawk sightings

08 February 2021   Issue #295

February 08, 2021

[The planetary nebula M 2-9, winds from a dying star. Credit: NASA / ESA / Hubble Legacy Archive / Judy Schmidt]

Subscribers flow with purpose, keeping winter at bay.

Is it hot in here, or is it just anthropogenic global warming?

Climate change is real, y’all

I downloaded a new weather app the other day (forecasts for the plains just east of the Rockies are hard — the changes as you move north/south are sudden and dramatic due to the different elevations of the mountains to the west affecting the weather patterns — and I generally like to look at a couple of different apps and average the results), and while I was checking it out I saw the forecast for the next few days.

Holy plunging mercury! Just last week it was shirtsleeve weather, and now it looks like we’ll be seeing a drop of about 60° F.

I knew even before checking what the culprit would be: Another meandering polar vortex.

You’ll be hearing a lot about it over the next few days, since it will affect essentially the entire United States, and in some places it’ll be very cold. 0° F for us is not too unexpected for this time of year, usually (though the mild weather we’ve had will make it seem a lot worse when it hits), but a lot of folks will be very surprised by this event.

My guess is you’ll also hear a lot of people in the media talking about this being the polar vortex, but as I’ve written before, that’s a little unfair. Yes, it’s the vortex, but more accurately it’s a meander in the jet stream confining the vortex, an excursion that drops the usually high-latitude frigid air down to lower latitudes.

The vortex is an area of low pressure over the Earth’s poles. The jet stream blowing from west to east fences in the bitterly cold air polar air, keeping it over the poles. However sometimes the winds in the vortex weaken and the stratospheric air drops down and heats up (as it falls it gets compressed by higher pressure, and when you compress a gas it heats up). This is called sudden stratospheric warming. This in turn can weaken the jet stream, which becomes wavy. When this happens fingers or blobs of cold air can move away from the poles, bringing that freezing air with it.

So yeah, it’s the vortex that brings that cold air, but the reasons behind it dropping down are a bit more complex.

[A diagram explaining the polar vortex. One the left is the usual situation, with cold polar air kept up north by the jet stream. On the right is shown what happens when the system weakens or even collapses, allowing a wavy jet stream to bring cold air south. Credit: NOAA]

I wrote about this a few years ago when the term became popular (it had been used for decades, but in 2014 or so bubbled up into the public consciousness). Also, there is some evidence that global warming exacerbates all this; the jet stream is powered in part by the change in temperature with latitude (essentially, it gets colder as you head north). The Arctic is warming at a rate much higher than lower latitudes, and that’s reducing that gradient. So it’s quite possible, ironically, that these sudden and vicious temperature drops are caused or at least exacerbated by global warming.

The thing is, air is complicated. It flows, and changes temperature and pressure and composition across the planet and with altitude, making its behavior fiercely complex such that it can do things that are unfamiliar and unexpected to folks not versed in the physics.

So if you hear anyone this frigid week say, “Wow, so much for global warming!” then set ‘em straight.

And check your own local weather to see what’s what! We’ll be prepping the horses and goats, making sure the former have their blankets and the latter have their heat lamps set up and working in their little house. Have a care with your pets, and make sure everyone is safe and warm.

[The goats (Sam, Batman, Clayton, and Jack Burton from left to right) and their shed, which is outfitted with heat lamps and a heated water bucket attached to a thermostat. Credit: Phil Plait]

Blog Jam

What I’ve recently written on the blog, ICYMI

[Sunday, February 7 is New Year’s Day on Mars. The reason why is… science! And a bit of arbitrariness, too. From Friday’s article. Credit: Getty Images / Fotonen / arsenic and NASA/ESA, J. Bell (Cornell U.) and M. Wolff (SSI) / Phil Plait]

Friday 5 February, 2021: Happy (Martian) New Year!

Red in Tooth and Claw

I live in rural Colorado, and we get nature here

I noticed a bedroom window curtain was closed while I was puttering around recently, so I threw it open, only to see this lovely raptor sitting on the roof:

[Credit: Phil Plait]

So I grabbed the camera and took a bunch of shots. It didn’t take long to figure out it was an immature Cooper’s Hawk, which are pretty common. Still, I hadn’t seen one up close before, so this was a treat. I can’t say for sure I’ve ever seen one before, but it’s very likely I’ve seen them flying around or in distant trees. I’m not great at IDing birds so who knows. 

It either didn’t seem to notice me or didn’t care I was there… until this shot:

[Credit: Phil Plait]

I feel seen.

Even so, it didn’t give me much attention, and went back to looking around, presumably for small birds to eat. You can see the solar panels to the left; usually there’s an assortment of LBJs (Little Brown Jobs) sitting there or in the gap under the panels, but not today, I’m sure.

Et alia

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