The weather here in Boulder has been pretty warm lately, and most of the snow is gone. I know that this can change at any moment (and in fact we’re due for more snow in a day or so), and NASA has provided a chilling but ethereally lovely reminder that this winter has been one to remember:

This image was taken by the Terra satellite on January 24, and shows what happens when there is a confluence of three conditions. The first is extremely frigid arctic air blowing down from the north west. The second is warmer waters in the Atlantic; the air above the water gets humid and rises into the colder air, condensing to form clouds. But the third is what’s needed to make this amazing rippling effect: a layer of warm air above the cold layer, called a temperature inversion. This acts like a ceiling for the rising, condensing air below. The clouds that form can’t rise any higher, so they roll east with the moving air, forming these "streets".

I think the effect of this image is heightened by the lack of clouds over land; it’s the ocean water that creates the clouds, so the skies were clear over the Atlantic seaboard, allowing us to see the snow-covered landscape. I like to think of how much meteorologists and climate scientists can learn from images like this, and of course that’s why we launch satellites like Terra into orbit. But I also don’t have too much of a problem just sitting back and admiring the beauty and artistry of our planet from space, either.

Image credit: NASA, Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center. Addition credit to my old pal Michael Carlowicz.

[This post is about the recent eruptions of Mt. Etna in Sicily. It's part of a set of gorgeous images of volcanoes as seen from space; the first three are of Etna. Click the thumbnail picture to get a bigger picture and more information, and scroll through the gallery using the left and right arrows.]

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I focus a lot of attention on NASA images of space, from our Moon to distant quasars. But NASA has a fleet of satellites which don’t look out, they look down, studying our home planet. One of the most amazing and beautiful of their targets are active volcanoes, like Mount Merapi in Indonesia:

[Click to hephaestenate.]

Merapi has been active for some time, blowing out hot ash and dust. This material can blast down the slope of the volcano in what’s called a pyroclastic flow, one of the most terrifying events I think the Earth can produce. It’s a wall of vaporized rock that can move very rapidly; Merapi’s flows have been clocked at 150 kph (90 mph).

In this image, taken with NASA’s Terra satellite on November 15, vegetation is shown in red (not green; the detector used by Terra can see light in the near-infrared, where plants are highly reflective, and this is colored red in the images). The ash and rock from the volcano appear gray. You can see where pyroclastic flows have flooded the forests on the volcano slope, destroying whatever plant life they touch. You can also see white clouds, and the gray plume of ash from the crater itself. Note that I have rotated the image so that north is to the left; I did this to make it fit better on the blog.

The long, feather-like finger to the right is the Gendol river, choked with mud flows called lahars which cascade down the mountain (much of the damage done by Mt. St Helens in 1980 was through lahars). Just below the river is a squiggly red region; that’s actually a golf course that’s been hit by a pyroclastic flow.

Images like this help scientists keep track of volcanoes in near-real time. While there is a chilling beauty to them, satellite images of volcanoes can be used to understand how they behave, and in a very literal sense help save lives. Yogyakarta, for example, is a city of nearly 400,000 people located not quite 30 km (18 miles) south of Mount Merapi. If I lived there, I imagine I’d be very happy indeed that people are keeping a close eye on the not-so-sleepy giant to the north.

Image courtesy NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team

The Earth is a writhing, seething cauldron of molten rock and metal. In some spots under the Earth, the pressure builds and builds, until something has to give, and KABLAM! You get a huge volcanic eruption.

On the other hand, sometimes the pressure just gets relieved nicely and steadily and politely, like in the Klyuchevskaya volcano in Kamchatka, Russia, as seen in this gorgeous Terra satellite image:

It’s a bit hard to tell here, but this is one teeny tiny part of a breathtakingly ginormous image that you can get by clicking the picture. Seriously, it’s 6000 x 8500 pixels.

And it’s stunning. This volcano, located in the far east side of Asia, erupts pretty steadily. (more…)

I’ve posted quite a few pictures from NASA’s Earth-observing Terra satellite over the past few months, some of them showing devastating natural disasters. But I never thought I’d post one that shows something so close to home.

This image was taken yesterday, September 6th, at about noon Mountain time:

That shows the plume of smoke from the Fourmile Canyon fire that I wrote about yesterday. The image is roughly 300 km (190 miles) across. The vertical dividing line is the actual edge of the Rocky Mountains; to the left (west) are the mountains, and to the right (east) is the start of the Great Plains stretching most of the way across the US.

The green smudge just to the south of the plume is Denver, and the smoke goes directly over Boulder… and my house. The fire is still going as I write this, but the winds have shifted and there is no longer a plume overhead. It smells like ash outside though, and the foothills — usually visible a few kilometers to the west from my house — are almost totally hidden.

I appreciate all the notes and tweets I’ve gotten, but we’re safe here. The fire is pretty far west of us, though we could see it poking over the first set of foothills last night. Creepy.

My brother-in-law has taken some amazing pictures of the fire from his house, located even farther to the east than where I am. This one shows the tops of the fires.

I’ll add that the sunset yesterday was desperately beautiful:

The smoke is made up of tiny particles of soot and ash. When blue light hits them, it scatters like a pinball off a bumper. So when you look to the Sun through the smoke, all the blue light has bounced off in a different direction, leaving only the redder light able to make its way straight to your eye. This happens on a lesser scale every night with particles in the air, making sunsets red. But this fire has really strengthened the effect, and the Sun went through myriad shades of red on its way down past the mountains last night. It was astonishing. Making it even more wrenching was knowing what was a causing it, and that there were people in the middle of all that smoke trying to put the fires out.

So far, there are still no reported injuries, though many homes have been destroyed and over 1000 people have been evacuated from the area.

My thanks to NASA_GoddardPix for the link to the Terra picture.

Holy Hurricanes. NASA’s Terra Earth-observing satellite caught this incredible and beautiful image of two major hurricanes in the western Atlantic ocean:

[Click to encategory5ennate.]

The northern one is Danielle, the southern Earl. This image, taken on the morning of August 29 (just a few hours ago as I write this) shows them off the US east coast. The image has the Leeward Islands — north of Venezuela and east of Puerto Rico — outlined on the western side of Earl. It’s not likely that either will have their eyes move over land, but they hardly need to for there to be an impact. Earl is Category 4 as it is now (150 mph sustained winds) but that’s near the eye; the edges will almost certainly sweep over the coast of North Carolina which still means lots of wind and rain. Most likely the coast will be spared a full onslaught, but if you live there, it’s best to be prepared for stormy weather.

Danielle is weaker and likely to wane more as it moves north; the waters are colder, starving it of the heat needed to sustain its shape and coherence. Incredibly, though, it’s 1000 km (600 miles) across. Still, it’s unlikely to have much of an impact on the US.

Chris Mooney at Discover’s The Intersection blog is keeping a close eye on these, as well as on Fiona, which is starting to gain strength in the Atlantic as well. Chris wrote the fascinating book Storm World, which is about hurricanes, so it’s no surprise he’s on top of this. You can also read NASA’s Terra page about this image to learn more.

One of the biggest predictors of global warming is the retreat of sea ice in the high northern latitudes. As oceans warm, the ice will take longer to form in the winter, and retreat faster in the spring. Scientists, therefore, have been watching the ice north of Canada very carefully.

What they’re seeing isn’t very hopeful.

This picture, from the Terra Earth-observing satellite, shows the state of sea ice as it was on August 17. This region is the so-called Northwest Passage — a waterway through the Canadian archipelago connecting the Atlantic and Pacific oceans. Usually the sea ice prevents regular trade routes from being utilized there. But over the past few years — <sarcasm>coincidentally</sarcasm> the time when scientists say global warming is accelerating — the sea ice has thinned considerably.
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