Volcanic ash: you can’t avoid if you can’t detect it

A post by Chris RowanIf you’re wondering what all the fuss is about with the “ashpocalypse” still shutting down most air travel in Europe, particularly in the light of several airlines trumpeting successful ‘test flights’ through the European skies, this is the only quote you really need to read:

Guy Gratton, head of Cranfield University’s facility for airborne atmospheric measurement, took a flight with fellow researchers to gather data.

Speaking as an aeronautical engineer, I would not want to be putting an airliner up there at the moment, said Gratton.

There is a lot of fairly nasty stuff there that we were running away from, knowing what we did. We have standard airline instruments on the aeroplane, we have got a storm scope and we have got a weather radar and they were looking straight through it.

Neither of those were seeing any of this stuff. It was only our specialist cloud physics instruments that were able to see the particles.

Jet engines do not react well with volcanic ash, but this would not be so much of a concern if commercial airliners could detect when they were flying into areas with dangerously high concentrations and divert around them, much as they do with storm systems. But the ash is too fine to be picked up on radar, meaning that normally equipped planes are effectively flying blind, reliant on external satellite and model data to steer a safe path. Do these data sources have the reliability, the resolution, and more importantly, the timeliness, to provide the pilots warning that they are flying into danger? A pilot’s first indication that something was wrong could well be when an engine shuts down.
Hopefully someone is seriously exploring solutions to this detection problem (can that specialised cloud physics instrumentation be deployed more widely, I wonder?), which is in the long term the only way to minimise disruption if Icelandic volcanism continues. In the meantime, it’s interesting that many people seem to be chafing more at the disruption brought on by a natural hazard with a clear and well-defined associated risk, than they do at restrictions in the name of protecting us from the much smaller chances of an undefined terrorist attack.

Categories: geohazards, public science, ranting
Tags:

Comments (21)

  1. eddie says:

    Thank you. Especially that last bit; so needed to be said.

  2. Lassi Hippel?§inen says:

    Since the stuff is so nasty, who not try to stop it at the source? You can’t seal the vent, but how about cooling the plume before it reaches the altitude where high winds will spread the ash all over Europe?
    I don’t have any numbers about how much heat the plume carries, but there is lots of cold water nearby to absorb it. You just need the right kind of equipment:
    http://en.wikipedia.org/wiki/Aerial_firefighting
    The airlines claim losses of around 200 million euros per day, so even a little help might be worth it.

  3. Julia says:

    Hell yes. Some of our teachers are stranded overseas at the moment and I’ve been doing a lot of cover today. We’ve also had power cuts on campus as the new building is being brought online. So there’s been a great opportunity to teach each class a bit about the volcano and why it’s dangerous. I have to say the majority of students have been satisfied that it is potentially a far more dangerous situation for aeroplanes than has been made out in the media.

  4. Lassi – Your idea of using water to cool the plume is an outrageously bad idea. The reason this eruption is producing so much ash in the first place is because the eruption is occurring in the presence of large amounts of water (glacier melt). The water rapidly quenches the magma producing the ash explosions. Adding more water to the mix is a bad idea from that point of view alone.
    Second, adding water to ash in the atmosphere will exacerbate the local effects of the eruption by essentially creating acid rain, which will damage crops, livestock, and even human health. See here for a recent article related to this phenomenon.

  5. CherryBomb says:

    The pressure seems to be building to get those planes back in the air ASAP, whether it is safe or not. Several airlines have already made some test flights to demonstrate that it is “safe.” I think I’ll take the train.

  6. Luna_the_cat says:

    They’re putting planes back in the air tomorrow.
    I hope for no tragedies.

  7. Robert S. says:

    Which “specialist cloud physics instruments” is the expert referring to? I assume some form of lidar?

  8. Lassi Hippel?§inen says:

    #7 Anne – I’m not suggesting to pour more water to the vent. Dump it on the plume. It shouldn’t cause any more ash to form, because all magma droplets have already solidified.
    The link you give is one more good reason why the effects should be limited to local scale. At the moment all those bad things are spreading to an area where half a billion people live and produce their food.

  9. Lassi Hippel?§inen says:

    … and Anne is at #4, not #7. Sorry.

  10. Chris Rowan says:

    Lassi – in that case I think your scheme faces a slight problem of scale. Check out this photo. It would be like trying to fight a forest fire with a water pistol. An ant’s water pistol.

  11. MadScientist says:

    I do worry that people will take the silly attitude that “hey, we didn’t crash on this flight, let’s ignore the London VAAC”. This is an old question and in almost 30 years we are still hardly any closer to answering it: what amount of volcanic dust is tolerable? Offhand that would depend on the particle size(s), the amount out there (g/m^3), and how long you fly through the stuff. I do not know of any public information on such tests on engines, nor can I imagine any manufacturers saying “you can fly our engines in these conditions” (lawsuit anyone?)
    LIDAR on aircraft may help if you can develop one to discriminate sand from ice and water droplets. RADAR is 100% useless although I hear that some manufacturers are trying to sell meteorological RADAR along with the claim that it can detect volcanic ash. Multichannel infrared imaging works well from space (and from the ground) but with numerous caveats – for example, with enough water adhering to the sand, the particles will appear to be ice. Also, if there is enough ice then the signal from the ice will mask the signal from the sand, making it appear that there is less sand or even no sand. In principle you can build a multichannel infrared imager to mount on aircraft (and it should work better than an imager on the ground).
    Keep in mind too that if you fly into the stuff, how do you tell if things will get better or worse in the path you are taking? Even if we did have appropriate instrumentation (which we don’t), the game would be to dodge the sand, not to fly through it.
    I am not aware of any funding going into developing such instrumentation; for over 20 years the attitude has been “it doesn’t affect us frequently”. As someone said in a meeting of experts on the subject almost 10 years ago now, “this will probably not change until we do lose a passenger aircraft”.
    @Lassi: The material actually cools relatively fast in the air; for somewhat small eruptions (which can still reach ~4km), infrared images show that the material cools down very quickly. The propulsion to great heights is primarily through the rapidly expanding gas rather than convection, so to arrest the explosion you need to cool the air; perhaps try the boiling point of nitrogen. The initial velocity is far greater than the speed of sound (you can calculate what speed is needed to launch an item 10km vertically without air resistance, this will give you an absolute minimum velocity which you know must be exceeded). Also, given the volume of material, that’s some incredible pump and plumbing you will need (and as I pointed out, it still won’t work because you cannot make the air cold enough). Even a small explosion is far more powerful than the largest conventional bombs we have; there is no stopping it.

  12. MadScientist says:

    @Robert S.: I doubt LIDAR is involved; airborne cloud instrumentation is typically nephelometers, condensation nuclei counters, scatterometers, that sort of thing. When investigating volcanic sand, particle impactors are sometimes carried to collect samples. However, in the past 30 years LIDARs have evolved to be extremely compact and even relatively low powered so I can’t rule out LIDAR, it’s just more likely not.

  13. Roman says:

    @MadScientist
    “I do worry that people will take the silly attitude that “hey, we didn’t crash on this flight, let’s ignore the London VAAC”.”
    I think the airlines prefer the risk of losing an aircraft than the certainty of losing 200,000,000 EUR a day.

  14. MadScientist says:

    @Roman: true, so if the industry insists on doing its own thing without factual evidence behind them, then groups such as the London VAAC should continue to issue its own advisories and have nothing to do with the whims of the industry. The relatives of people who chose to travel despite a VAAC advisory can then sue the airline operators for neligence causing death. Any victims on the ground can also sue for damages and claim punitive damages on top. At the moment everything is done on a collegial basis; some airlines such as Qantas in Australia have a very good relationship with the VAACS and still seem to shut down and accept the financial losses rather than fly until a disaster occurs. I don’t know if there are any actual laws anywhere which require pilots or airline operators to follow the advice of a VAAC.

  15. Lassi Hippel?§inen says:

    Chris #10: There may be a problem of scale, as I mentioned in my first comment, but I’d like to see it expressed in numbers, not hand waving.

  16. Luna_the_cat says:

    @Lassi Hippel?§inen — the photo that Chris linked. I think perhaps additional explanation is in order. See that little bright white object that looks a bit like a bird, in the middle of the photo?
    That’s an airplane.
    Given this, what precisely would you recommend dumping water on the plume from, that would make a difference?

  17. MadScientist says:

    @Lassi: Let’s say the melt is at 900C (which is on the low end) and the volcano ejects a mere 100 metric tons of sand per second (~50 cubic meters per second). Let’s say the specific heat of the sand is about 800J/kg/C (water is about 4200J/kg/C). We won’t count the water content of the plume because that would have removed some energy already, so we look at the total amount of water needed to cool the ejecta to 60C (so it doesn’t burn me). Let’s say you have water at 0C to pour on. Given 1kg of sand at 900C, cooling to 60C requires the removal of (900-60)*800J = 47100J/kg. Converting that to volume of water required at 0C: 47100/4200*(60-0) = 673kg (~673L) per kg of sand. Since we’re looking at 100,000kg sand per second, you need 67,300,000 liters per second of freezing cold water. That’s 67 megaliters per second – that’s larger than the capacity of many dams supplying moderately large cities. You will be exhausting a dam’s full capacity each second and we’re only talking about a very small volume of ejecta here. You can safely bet that the glacial melt does not amount to 67ML water per second in the ejecta; let’s be extremely generous and say you only have to supply an additional 60ML per second. (1) where do you get the water, (2) how do you install the infrastructure, (3) where do you get the power to move the water ? I think Chris was being very generous with the ant’s water pistol.

  18. Lassi Hippel?§inen says:

    @16: yes, I noticed the plane, but without knowing what size it is, and at what height, the picture doesn’t prove anything. Forest fires can be big, too.
    @17: thanks, that’s what I was asking.
    There are some things that can be argued. Is that 100 tons/s the output of ash that gets into the plume? Is the ash still at 900C when it enters the plume? And most importantly, how much the ash needs to be cooled to prevent its rise to high winds? (We are not worried about burning anything – the ash will be cool by the time it lands.) The plume cools by itself when it rises, and at some point looses its buoyancy, but I don’t have any estimate on the altitude where it becomes an international problem, i.e. how cool it should be from the start. Athmospheric phenomena are quite nonlinear. Anyway, smoke from a chimney can be near 200C, and it doesn’t rise even to a kilometre.
    But even if your estimate were an order of magnitude too high, the numbers still look pretty bad. The problem isn’t availability of water (there’s lots of it in the sea) but transporting it to the plume.

  19. MadScientist says:

    @Lassi: The volcanic ash is usually estimated by volume of the sand which falls to earth but it is also possible to estimate the actual mass using other techniques and without using estimates of the volume. It typically leaves the vent at a much lower temperature than the melt, but even if you only guess at numbers you can see that there are still problems with the idea. For example, let’s say at a temperature of 600C the plume rises to 12km but you want to keep the plume below 6km and to do this (hypothetical only; I’d have to spend hours to work out actual equations and to solve them) you had to reduce the plume temperature by 100C. That’s still about 1/9 of the original calculated water volume, so still about 6.7ML per second. It is not safe to get near an erupting volcano either; you can get a ‘surge’ (or similar phenomenon, the pyroclastic flow) which is composed of hot volcanic gas and sand and can easily travel over 100km/h along the ground. Add to that the fact that the water you pump in has got to go somewhere. We humans are helpless against even the smallest of volcanic eruptions; the best we can do is get away from the volcano.

  20. jjanilu says:

    The technology for real-time detection and measurement of volcanic ash has existed for years. Dr. Fred Prata created the technology which is now being commercialized as both ground-based and airborne technologies.

  21. JG says:

    I agree with Lassi, I would think that you could just have planes flying that eject mist in a pattern around the aircraft, above or near the top of the plume that could certainly make a dent in the size if the plume. Can one scrub the sky with water and cause the ash to fall into the sea?
    I was thinking similar to the firefighting aircraft, but more specialized. First of all would have to have engines that can deal with the ash itself. The planes could fly slow.
    Generally the planes land on the water I believe, pump their tanks full, and then take off again. It would take a very specialized craft, but for 200,000,000 euros a day, I bet I could come up with one ;)
    The scale could be a problem, but I don’t think it would hurt to try. Some scientists were claiming that the ash in the ocean is good for the sea life. http://volcanoes.usgs.gov/ash/properties.html Here is a website that shows that the particulate is much smaller farther away from the volcano. I think the mist could help.
    I was also wondering about silver iodide cloud seeding, but that certainly has had questionable results in the past.