Tag: fire

Pyrocumulus cloud

By Phil Plait | June 24, 2012 7:00 am

As I write this, the High Park fire is the second largest wildfire in Colorado history, currently at 75,000 acres (over 300 square kilometers, or 115 square miles). It’s been burning more than a week, and fighting it has been difficult due to dry conditions, wind, and oppressive heat in the area.

I can see the fire from Boulder, but yesterday I got a really good, if terrifying, view of it driving home from the airport. There was nothing but farmland and one low range of hills between me and it. I stopped and took some pictures with my phone:

I was about 55 km (35 miles) south of the fire when I took this. Note how the plume is whitish and looks like a storm cloud. I discovered there’s a word for this: pyrocumulus; "pyro" means fire, and "cumulus" is Latin for heap or piled up. Cumulus clouds are the ones that are the big puffy cauliflower-shaped ones. The puffiness is from convection, which is when hot air rises and cold air sinks. Usually, warmer moisture-laden air punches upward into the cooler air above it. The water condenses, and all the little convection cells give the cloud that lumpy appearance.

In this case, the fire is hot, and the air is thick with smoke as well as water from the efforts to put it out [UPDATE: As Dan D points out in the comments below, water from the vegetation contributes to this as well]. It rises rapidly, forming the pyrocumulus cloud. They’re usually grey, but I suspect the towering cloud I saw is white due to the water vapor. The smoke plume from the fire is blowing to the east (right), and stretches for a long, long way:

It actually extends well off to the right, outside the frame of this picture. The smoke plume is noticeably reddish to the eye. I was cycling up that way last week, just the day after the fire started, and the smoke plume was reddish-brown with a blue tinge to it around the upper edges. I suspect this is due to scattering. Incoming light of all colors from the Sun hits the cloud. Longer wavelength red light penetrates deeply into the cloud, but blue light only gets a short way in before scattering off the smoke and ash particles. Think of them like blue photon ricochets, hitting the cloud and bouncing off in all directions.

The upshot is that we see blue light coming from the edges of the cloud where it gets scattered, but the lower part of the cloud looks redder because of the intrinsic color of the smoke, and also because only the red light form the Sun gets through it (similar to why sunsets look red). The overall effect is eerie, and unpleasant.

Which fits. This fire is pretty bad, and it’s joined by many other fires in Utah and New Mexico, not to mention in other countries like Russia. I’ll note that it’s difficult to pin this down to global warming, but as the planet does warm, different weather patterns will make some places wetter, others drier. One commonly predicted outcome is more and bigger fires, and it does seem we’re approaching or breaking a lot of records lately.


Related Posts:

- Boulder fire from space
- Sunset on an alien world
- … I meant, Stardust "@" Home (more about this blue/red light effect from scattering)
- The twice reflected Moon light

CATEGORIZED UNDER: Miscellaneous, Pretty pictures

Did a telescope start a house fire in Arizona?

By Phil Plait | June 7, 2012 6:30 am

Well now, here’s a story you don’t hear every day: a telescope in Carefree, AZ may have caused a fire that burned part of a house. KNXV TV in Phoenix carried the story. I have comments below.

There’s are also articles at AZCentral and at Firegeezer with some more details.

My first reaction was, "No way." Then I looked into this more, and now I think the ‘scope may have indeed been the culprit.

The telescope is a design called a Schmidt-Cassegrain, or just SCT. I have one myself! It’s a tube with a big mirror (called the primary) in the back that’s curved. It reflects light back up the tube. At the top of the tube is a flat piece of glass (called a corrector plate) with a smaller mirror embedded in the middle. This reflects the light again down toward the bottom of tube, where it passes through the hole in the big mirror and into an eyepiece (and from there into your eye or camera). The inset diagram here shows how this works; click to newtonianate.

I called the Carefree fire department, and talked to Colin Williams, their Press Information Officer. He was very helpful, and told me more of what happened. Read More

CATEGORIZED UNDER: Astronomy, Miscellaneous

Explosion in Argentina following a "ball of fire from the sky"

By Phil Plait | September 26, 2011 9:32 am

[Update: It looks like the cause of this was a gas bottle exploding, and not a meteorite. See the update for 21:15 UT below).]

A deadly explosion and fire occurred in Argentina overnight, reportedly killing one woman and injuring several others. Two homes, a store, and several vehicles were destroyed or damaged.

The thing is, while it’s not clear what caused this incident, several people said they saw a ball of fire descend from the sky when it happened.

Neighbors’ accounts describe a ball of fire coming from the sky as the cause of the explosion. The chief of the firefighters, Guillermo Pérez, however, said the "causes remain unknown" and that "gas containers were found intact," ruling out a gas related incident.

Other reports are similar; in that article the ball of fire was described as being blue. I know a lot of folks will think this was caused by a meteor, but it’s a bit early to run with that yet. For one thing, it could’ve been a small plane on fire, for example; this happened very early in the morning (2:00 a.m.), and from the reports I’m seeing it’s not clear if the witnesses were already awake when they saw this or were awakened by it. Eye witness reports are notoriously unreliable, and it can’t help if the witnesses were suddenly woken up.

[Update (17:30 UT): This is looking less like a meteorite to me; this news story has a witness saying he saw the blue fire after hearing the explosion, and after he went outside to see what was what. Thanks to JoseManuelp2 for the link.]

As testament to that, I’m seeing some reports that the ball was red, and a picture was posted to the imaging site yfrog claiming, without any any supporting evidence, to be a shot of it. I include it here; note it’s very dark, out of focus, and very low resolution (from the pixelation). I have no clue what this picture shows, but I have my doubts it’s a fireball. I expect we’ll be seeing lots of rumors and things like this today.

[Update (21:15 UT): The image shown here of the red fireball is a hoax, and the man responsible for it has been arrested. Also reported in that link is that there were gas bottles secretly hooked up to a pizza making stove in a nearby house, and that this may be the cause of the explosion. I expect that is the final straw on this story -- enough evidence is piling up that this was not something form space, or even from the sky; it was some kind of terrestrial event, as expected.]

The explosions and devastation appear to be very real, though. This is the only video I could find on YouTube, and it has no audio, but it shows the aftermath:

I don’t see any obvious airplane wreckage, but it’s hard for me to see that a meteorite impact would’ve done this; for it to have been big enough to cause this much devastation, there would’ve been a big crater as well (like the one that hit in Peru a couple of years back). None is evident, so I’m strongly of the opinion something more terrestrial was to blame here.

I won’t be surprised to hear people asking if this was from the UARS satellite, too. However, that’s pretty much impossible; the satellite came down Friday night, and there couldn’t have been pieces of it still in orbit two days later. Also, again, the type of destruction seen here is unlikely to have been from just a simple impact.

Hopefully we’ll find out soon. If you hear anything please leave a comment below (with a link if you have one), and I’ll post an update when I learn more.

[Update: A grass fire in Texas Saturday night has been reported, and it's claimed to be linked to something falling from the sky. Again, a meteorite is extremely unlikely there, since it would take a big impact to ignite fires. Stuff like this happens all the time, and remember Texas is extremely dry right now. I would guess this was fireworks, but there's not much info on this story either. Thanks to Baron Grim on Twitter for the story.]

Tip o’ the Whipple Shield to Antropomorficah on Twitter. Image credit: screen grab from embedded C5N video.


Related posts:

- UARS down over the Pacific ocean
- Meteorite mayhem III: solved
- Peruvian “meteor” freaks out medi
- Midwest megameteor makes media madness
- What a falling star looks like… from space!

CATEGORIZED UNDER: Astronomy, Skepticism

Boulder fire damage seen from space

By Phil Plait | August 3, 2011 7:00 am

As I write this, storm clouds are gathering in the west. That’s a pretty common situation here in Boulder, Colorado, in the summer. We get fine, clear mornings, and sometimes rain in the afternoon. In general big storms aren’t exactly rare, but this summer we’ve been getting pounded. On my bike rides it’s been routine to see the creeks in the area swollen to the point of overflowing.

But this summer, that situation has turned more dangerous. We’ve been getting some serious flood scares, and the reason may not be obvious to people who don’t live in the area: fires.

Last year, the Fourmile Canyon area north and west of Boulder burned pretty vigorously for many days. The smoke plume was visible from space, and it caused a lot of local grief. What wasn’t clear to me at the time was how this would affect flooding.

The image above, taken on June 7, 2011, is from NASA’s Earth Observing-1 satellite, and is a combination of far-infrared and visible light. Water (reservoirs and lakes) shows up as purple in this false-color image, vegetation is mostly green, and red/orange shows the fire damage. You can see Boulder to the lower right of the burned area.

When fire burns off all the plants, there’s nothing to hold the rain water in when we get storms. The water all washes downhill, in this case into the Fourmile Creek. That runs into the Boulder Creek, and that, well, here’s a natural color image which shows why that’s bad:

Read More

CATEGORIZED UNDER: Miscellaneous, Pretty pictures

Boulder fire from space

By Phil Plait | September 7, 2010 11:46 am

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:

terra_boulderfire

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:

Smoke and Sun

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.

CATEGORIZED UNDER: Miscellaneous, Pretty pictures
MORE ABOUT: Boulder, fire, Terra

Another tornado MADE OF FIRE! Waiting now for tornado made of locusts.

By Phil Plait | August 30, 2010 12:30 pm

When I posted the awesome video of a fire tornado last week, I had only heard rumors of such things. Apparently, they’re more common than I thought.

Here’s another amazing video, and this one is even better: it’s longer, and you can see the rotating smoke cloud around the column of fire!

This really is a fantastic demonstration of how microscale weather works. Imagine: a fire starts. As the air is heated above the fire, it rises, and the upward motion can be very strong. This leaves a lower pressure spot at the fire, and the air from outside the fire rushes in to fill the gap. The air is very turbulent, and as the inward-moving air from one side hits air coming in from the other, swirls can form. These get amplified by the constant gale of air, and rotation on a larger scale can get started and sustained. The whirlwind gets pumped by the hot air rising, and the next thing you know you’ve got a full-blown tornado of fire.
Read More

CATEGORIZED UNDER: Astronomy, Cool stuff, Geekery, Science
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