Bad Astronomy

Snowpocalypse 2011 from space!

Just in case you haven’t seen enough snow this week, NASA and NOAA have released an amazing video made from GOES 13 weather satellite images. I present to you Snowpocalypse 2011:

[Set the resolution to 480p to see it best.]

The animation goes from January 31 to February 2, and you can really see how the wet air from the ocean and Gulf of Mexico gets slammed by incredibly cold arctic air that had screamed south, creating this enormous storm front that swept across the nation. I was in Nebraska when this hit; the night before it had been unseasonably warm, but then temperatures dropped a lot – like 40°C (65°F) – by the next day. Nebraska looked like another planet. Boulder didn’t get much snow (you can see from the animation that snow was mostly east of Colorado) but the temperatures were so cold they had to cancel schools; the fuel mix used in school buses wasn’t rich enough to start the engines!

The GOES satellites (Geostationary Operational Environmental Satellites, just so’s you know) orbit the Earth over the Equator at a height of about 40,000 km (24,000 miles) above the surface. This makes their orbital period 24 hours, so they orbit once for every time the Earth rotates once. From their point of view, it’s as if they are hovering over one spot on the Earth – which is why this is called a geostationary orbit* – making this a very useful orbit for weather and communication satellites.

In the animation, the Earth’s surface doesn’t move, but you can see the weather flowing over it. You can also see the day/night line, called the terminator, sweeping across as well. In the winter, with the Earth’s north pole tipped away from the Sun, the dawn terminator is tilted southwest to northeast (lower left to upper right in the animation)… and the dusk terminator is the other way (upper left to lower right). Confused? Yeah, three dimensional spinning balls get that way. I had to use an apple and a lamp to make sure I was getting this right.

As I write this, more snow is likely today, and we can predict this pretty well in large part because of satellite data like these. Think of how much money is saved, how many lives are saved, because of technology like this. The next time someone asks what NASA or NOAA or just the government in general) has done for them, remind them of this.


Tip o’ the parka hoodie to NASA’s Twitter feed.

* Geostationary orbits are a class of geosynchronous orbits, which is any orbit that lasts 24 hours – well, to be more precise, it’s actually Earth’s sidereal rotation period of 23 hours 56 minutes 4 seconds. However, such an orbit can be tilted, or non-circular, so the satellite may appear to wander as it speeds up and slows down in its orbit… though it generally hangs over the same area of the Earth’s surface. This is actually pretty cool stuff, and you might like reading about it more. I am endlessly fascinated by such things!