New study calculates the speed of ice formation

From Princeton:

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, provide insight into the mechanism by which water transitions from a liquid to a crystalline solid.

Understanding ice formation adds to our knowledge of how cold temperatures affect both living and non-living systems, including how living cells respond to cold and how ice forms in clouds at high altitudes. A more precise knowledge of the initial steps of freezing could eventually help improve weather forecasts and climate models, as well as inform the development of better materials for seeding clouds to increase rainfall.

Using a computer model to explore how water molecules connect and nucleate into ice crystals, the researchers found that two types of ice compete for dominance during nucleation: cubic ice (blue) which is less stable, and hexagonal ice (red), which is stable and forms the majority of ice on Earth. Nucleation occurs when water molecules come together to form blobs (pictured above), which grow over time (left to right). Eventually hexagonal ice wins out (not shown). The researchers found that adding new cubic features onto an existing crystalline blob gives rise to nuclei that are more spherical, and hence more stable. In contrast, adding hexagonal features tends to give rise to chains of hexagonal cages that make the nucleus less spherical, and hence less stable. CREDIT Images courtesy of Amir Haji-Akbari, Princeton University.

Using a computer model to explore how water molecules connect and nucleate into ice crystals, the researchers found that two types of ice compete for dominance during nucleation: cubic ice (blue) which is less stable, and hexagonal ice (red), which is stable and forms the majority of ice on Earth. Nucleation occurs when water molecules come together to form blobs (pictured above), which grow over time (left to right). Eventually hexagonal ice wins out (not shown). The researchers found that adding new cubic features onto an existing crystalline blob gives rise to nuclei that are more spherical, and hence more stable. In contrast, adding hexagonal features tends to give rise to chains of hexagonal cages that make the nucleus less spherical, and hence less stable. CREDIT Images courtesy of Amir Haji-Akbari, Princeton University.

The researchers looked at the process by which, as the temperature drops, water molecules begin to cling to each other to form a blob of solid ice within the surrounding liquid. These blobs tend to disappear quickly after their formation. Occasionally, a large enough blob, known as a critical nucleus, emerges and is stable enough to grow rather than to melt. The process of forming such a critical nucleus is known as nucleation.

To study nucleation, the researchers used a computerized model of water that mimics the two atoms of hydrogen and one atom of oxygen found in real water. Through the computer simulations, the researchers calculated the average amount of time it takes for the first critical nucleus to form at a temperature of about 230 degrees Kelvin or minus 43 degrees Celsius, which is representative of conditions in high-altitude clouds.

They found that, for a cubic meter of pure water, the amount of time it takes for a critical nucleus to form is about one-millionth of a second. The study, conducted by Amir Haji-Akbari, a postdoctoral research associate, and Pablo Debenedetti, a professor of chemical and biological engineering, was published online this week in the journal Proceedings of the National Academy of Sciences.

“The main significance of this work is to show that it is possible to calculate the nucleation rate for relatively accurate models of water,” said Haji-Akbari.

In addition to calculating the nucleation rate, the researchers explored the origin of the two different crystalline shapes that ice can take at ambient pressure. The ice that we encounter in daily life is known as hexagonal ice. A second form, cubic ice, is less stable and can be found in high-altitude clouds. Both ices are made up of hexagonal rings, with an oxygen atom on each vertex, but the relative arrangement of the rings differs in the two structures.

“When water nucleates to form ice there is usually a combination of the cubic and hexagonal forms, but it was not well-understood why this would be the case,” said Haji-Akbari. “We were able to look at how the shapes of ice blobs change during the nucleation process, and one of the main findings of our work is to explain how a less stable form of ice is favored over the more stable hexagonal ice during the initial stages of the nucleation process.”

Debenedetti added, “What we found in our simulations is that before we go to hexagonal ice we tend to form cubic ice, and that was very satisfying because this has been reported in experiments.” One of the strengths of the study, Debenedetti said, was the innovative method developed by Haji-Akbari to identify cubic and hexagonal forms in the computer simulation.

Computer models come in handy for studies of nucleation because conducting experiments at the precise temperatures and atmospheric conditions when water molecules nucleate is very difficult, said Debenedetti, who is Princeton’s Class of 1950 Professor in Engineering and Applied Science and Dean for Research. But these calculations take huge amounts of computer time.

Haji-Akbari found a way to complete the calculation, whereas previous attempts failed to do so. The technique for modeling ice formation involves looking at computer-simulated blobs of ice, known as crystallites, as they form. Normally the technique involves looking at the crystallites after every step in the simulation, but Haji-Akbari modified the procedure such that longer intervals of time could be examined, enabling the algorithm to converge to a solution and obtain a sequence of crystallites that eventually led to the formation of a critical nucleus.

Even with the modifications, the technique took roughly 21 million computer processing unit (CPU) hours to track the behavior of 4,096 virtual water molecules in the model, which is known as TIP4P/Ice and is considered one of the most accurate molecular models of water. The calculations were carried out on several supercomputers, namely the Della and Tiger supercomputers at the Princeton Institute for Computational Science and Engineering; the Stampede supercomputer at the Texas Advanced Computing Center; the Gordon supercomputer at the San Diego Supercomputer Center; and the Blue Gene/Q supercomputer at the Rensselaer Polytechnic Institute.

Debenedetti noted that the rate of ice formation obtained in their calculations is much lower than what had been found by experiment. However, the computer calculations are extremely sensitive, meaning that small changes in certain parameters of the water model have very large effects on the calculated rate. The researchers were able to trace the discrepancy, which is 10 orders of magnitude, to aspects of the water model rather than to their method. As the modeling of water molecules improves, the researchers may be able to refine their calculations of the rate.

###

The study, “Direct calculation of ice homogenous nucleation rate for a molecular model of water,” by Amir Haji-Akbari and Pablo G. Debenedetti, appeared in the journal Proceedings of the National Academy of Sciences Early Edition online August 3, 2015.

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80 thoughts on “New study calculates the speed of ice formation

      • So they say that their model predicted nucleation in a microsecond which is ten orders of magnitude slower than real life, so it rally takes 100 atto-seconds.
        And we were worrying about how long it takes.
        Wait till I get my snow shovel ready, if it is going to be that fast.

  1. “The simulations, which were carried out on supercomputers, ….”
    Are they the ones which make the same errors as ‘normal’ computers, but quicker?

    • Yep. I just love when the UK’s Wet Office say things like “this supercomputer is capable of making over a trillion calculations a second!”, as if that’s some bizarre way of guranteeing the correct result. As an engineer, getting the specific design philosophy right is crucial, otherwise no amount of computing power will give the right solution! Climate scientists seem not to realise that!

    • Well Mother Gaia knows exactly when water Is supposed to freeze, and it will do so at the proper time, when she is ready for it.
      So we don’t need to calculate it; It will happen when it is due.
      Unlike Zurich, Mother Gaia doesn’t wait around until an average Temperature suddenly happens, and it is time to freeze. It happens instantaneously, when it is supposed to.

      • Instead of a supercomputer, could they have maybe saved some money and time by using a clear jar and a camera?

  2. Two good things:
    1) At least there was passing mention of empirical data. The computer model alone was out by 10 orders of magnitude and they correctly adjusted their water model until it matched the empirical, an adjustment they refuse to do using the empirical of global temperature records in the IPCC.
    2) I like that they are going to square one – how does water freeze. The whole corpus of climate science needs to sweep out their politico-speculative trash and start at such fundamental science levels.

    • I saw nothing in this article that says they corrected the water model. “As the modeling of water molecules improves, the researchers may be able to refine their calculations of the rate” They have recognized that the model is off by 10 orders of magnitude, but I am sure that will not stop “scientists” from using it.

      • Well it can be used for some things. Just not for predicting if snow will form.
        This modelling is on the scale where models can be realistic. There aren’t so many other factors confounding them. It’s not like trying to model the human brain or the world economy or the entire atmosphere and oceans.
        It seems like a sensible but difficult thing to try and do. Proper science.
        My only concern is that they found the rate of ice formation obtained in their calculations was much lower than what had been found by experiment and then – they adjusted the model to fit reality.
        Not stupid, by any means. But they could have considered that they may have missed a significant factor. For example, did they consider the seeding of nucleation by salt or dust?
        We know that happens after all.

      • “The researchers were able to trace the discrepancy, which is 10 orders of magnitude, to aspects of the water model…” I take this to mean that they know what these aspects are at least and a redo would give better results.

      • Gary, “A redo would give better result” … They and you do not know that. The purpose of this study was: “The main significance of this work is to show that it is possible to calculate the nucleation rate for relatively accurate models of water,” Even though the result was 10 orders of magnitude off they consider it a success. I find this funny and sad at the same time.

      • So are you suggesting that they are homing in on the order of magnitude, of the order of magnitude, using their Terra flop.
        Excuse me; that’s their computer.
        Well it used to be in particle physics experiments that went on where I went to school, that if you got the order of magnitude correct, you were on to something.

      • MCourtney writes: “But they could have considered that they may have missed a significant factor. For example, did they consider the seeding of nucleation by salt or dust?”
        MCourtney is right on target. When I first read the head post, my first reaction was that focusing solely (or at all) on homogeneous nucleation and ignoring heterogeneous nucleation was a rookie mistake, particularly when their calculated nucleation rates fell so short of those obtained experimentally.
        Solidification requires a reduction of Gibbs Free Energy (GFE) which itself (in simple terms) is a trade-off between the volumetric GFE reduction associated with the phase transition (~r^3) and the surface energy increase (~r^2). This competition produces an energy barrier peak at the so-called critical radius (r*) that must be overcome by a nuclei to become viable: this tradeoff lowers the probability formation and and increased the time-constant for nucleation This is a simple description of classical nucleation theory.
        OTOH, heterogeneous nucleation involves the presence of imperfections, be they scratches on the walls of a liquid container, an exogenous inclusion in a molten metal, or dust and aerosols in a cloud. To get a first hand appreciation of this more typical nucleation process, albeit for a bubble, just pop a cold one — as I’m doing now — and watch the bubbles of your brew emanate from the scratches and nicks on the walls your glass.
        What I’ve written is certainly nothing new; I was taught this as an undergraduate in the 1960’s and did my graduate work in solidification in the 70’s. I suspect that the researchers of the subject paper focused on homogeneous nucleation because they could do it rather than because it was correct! As you can probably surmise, handling defects (sizes, geometry, probability of occurrence, movement) is extremely difficult. But maybe I’m cynical.
        Dan

  3. Does the model account for the varying energized radiation present at the altitudes it simulates? If not, it is not as realistic as they claim.

  4. “Seeding” is something that depends on many variables being right in order for it to work to the extent that the rain it produces is worth a damn. Knowing how fast water freezes in microseconds tain’t one of them. This seems to me to be a tremendous waste of dollars. I’ve had about enough of this kind of research when other areas are so much more in need of inquisitive and creative researchers and engineers. I wonder who the underling was that was assigned to this piece of worthless super computer using “who gives a sh**” low hanging fruit.

    • I’m looking at the want s in the paper, now to see if some company is wanting to hire somebody with a PhD in the speed of ice formation.
      It might be valuable for use in refrigerators that use NO electricity at all. The more ice blacks you can make, the more ice boxes you can sell.

  5. This may be something to take into consideration when discussing the model.
    “Even with the modifications, the technique took roughly 21 million computer processing unit (CPU) hours to track the behavior of 4,096 virtual water molecules in the model, which is known as TIP4P/Ice and is considered one of the most accurate molecular models of water. The calculations were carried out on several supercomputers, namely the Della and Tiger supercomputers at the Princeton Institute for Computational Science and Engineering; the Stampede supercomputer at the Texas Advanced Computing Center; the Gordon supercomputer at the San Diego Supercomputer Center; and the Blue Gene/Q supercomputer at the Rensselaer Polytechnic Institute.”
    Now think about the size of their modeled construct
    for a cubic meter of pure water”
    Quit a bit of computer power for a simulation of just “one cubic meter of water”
    I hope they continue.
    michael

  6. The current interglacial is overdue to end. I suggest scientists work on ways to halt the ice sheets. Possibly a microbe that can live on the ice and emit squid ink.

  7. The primary events in crystal formation has been a fundamental problem in pure chemistry for a very long time. One aspect of this problem is how many molecules do you need to throw together before you get a stable solid formed from the liquid (or gas)? Of course, once you get that little bit of stable solid, the crystal can grow in an orderly fashion from there. But how do you get that solid in the first place when all your intermediate structures are unstable and likely to just fall apart again? So the problem is very interesting and quite difficult, and is at base, fundamental as to how molecules behave.
    As far as seeding and nucleation sites go, it is so much easier to have an energetic active site where several molecules can come together all at once and produce the phase change. This is common experience in the lab where you use boiling chips for smooth boiling, and when growing crystals, the bath needs to be seeded in one way or another. Otherwise, superheating, supercooling and supersaturation effects abound. Trying to study the phase change in the absolute absence on external nucleation is quite a different problem.

    • I agree that it is interesting (and difficult), but I don’t see just how they compared this model back to reality. Article is paywalled. Supplemental materials available, but don’t address my question.
      I guess you go where the money is too –
      The research was funded by the National Science Foundation (Grant CHE-1213343) and the Carbon Mitigation Initiative at Princeton University.

    • Decades ago, when I was a biochem grad student, I heard the following (probably apocryphal) story:
      For years an undergrad organic synthesis class had been conducted in an old but still useful laboratory. The students’ newly prepared compounds easily crystallized out of solution, ready for analysis or subsequent steps. Then the class was moved to a brand new lab in the brand new chemistry building, but for the entire first semester, none of the students’ products would crystallize. The flasks sat day after day with nothing happening. Finally, the professor and his students carried the flasks to the old lab, exposed them to the air, and (as the story is told) POOF! POOF! POOF! crystals appeared at last. Apparently the old lab was “contaminated” with minute seed particles of all the compounds prepared over the previous decades.

      • Well many years ago, I visited the factory of Bliley Electric, in Erie Pennsylvania; who were at the time (may still be) the manufacturers of the very best quartz crystals for oscillators, in the world; specially the ” Warner ” Crystal, which was a special 2.5 or 5 MHz AT cut crystal for frequency standards. But they made all kinds of crystals out of quartz.
        Every now and then, there would be a terrific noise and the whole factory would shake, and then it would all subside.
        The factory was actually inside an old building of the Erie Pennsylvania railroad station, and when the train outfit, would close another route, and lay off some people, Bliley would take over the offices and hire a couple more people.
        Eventually, they built a new plant at a different location, and for a long time, they were unable to deliver crystals to spec, because they were trying to do it in a place that didn’t shake and rattle.
        Well they did eventually get recalibrated, and for all I know, they still might make the best quartz crystals in the world.

    • I grant that this is a problem. Now, if you would be so kind, tell me the utility of finding this answer to this at the cost of million$. I realize that science doesn’t actually have to benefit to the race or planet, but when we have a world full of real problems, don’t you think it would be appropriate to try to solve those instead of finding a niche you can work in that has no one else in it and no immediate value of any type to the world in general? Especially since it is being funded by money taken from tax payers – against their will – that they need to solve their own problems?

      • if you would be so kind, tell me the utility of finding this answer to this

        *sigh*
        Yes, I will be so kind. Pure research seeks a better understanding as to how things work at a fundamental level. The knowledge gained is fodder for the applied research people. If the base of pure knowledge runs out, the applied people run out of new ideas. By the same token, the applied people notice something new and unexpected, it gives the pure research people something new to think about.
        All of this provides the engineers with a wealth of new material for reduction to practice, and ultimately, process and product.
        Even as far back as the early 1970s, people were whining “Why are we spending millions sending men into space when we have needy people right here on Earth?”. They would overlook the fact that by then welfare payments were vastly larger than the space exploration budget and produced nothing at all in return. Meanwhile, satellite based hurricane monitoring was saving thousands of lives and billions in property damage every year. And these same people seemed not to notice or care how that happened at all.

  8. Lazy science.
    It’s hard to take actual measurements, so let’s try a computer model.
    It’s hard for the computer to measure each step, so let’s only measure once in a while.
    The computer is off by 10 orders of magnitude, but that’s because of the water molecule modeling and not due what we’re doing.
    Hey, you guys doing water molecule modeling, get to work!

    • No.
      They have the actual measurements. Now they want to know why those rates are as they were measured to be.
      So they try to see how sticking things together works (we know about hydrogen bonds) and whether the rates are the same as expected. They weren’t. But they know that now.
      That’s progress. That’s science.

    • We have a theory and a model, the model sorta works but needs improvement to match observations.
      I’m ok with attempts that are not good enough, disappointing, or a failure, being published. It leads to the next better step. Otherwise you have to contend that Newtonian Physics should not have been published until Quantum Mechanics improved the accuracy.

      • Tom O: How are other researcher to know what didn’t work if failures are not published? Should they all spend their time repeating the same thing others determined to not quite work or would they be better off trying something else?

    • Well clearly they need to run their simulations on a DEC PDP8. I do believe that it runs at exactly 10 orders of magnitude slower than the ziggaflop they are trying to use.
      I’m sure that is their problem. Just not enough time to grow crystals.

  9. “Debenedetti noted that the rate of ice formation obtained in their calculations is much lower than what had been found by experiment … 10 orders of magnitude”.
    The good news: We managed to do the calculation!
    The bad news: The results are wildly wrong.
    I suppose this constitutes success if it means they can get their grant renewed.
    So what is new here? People have been doing molecular dynamics simulations of this type for at least 20 years. But no one ever got a nucleation event before, implying that there was something wrong with the computer models. These guys only got an event by throwing an insane amount of computer time at the problem. So now we know there is something wrong with the computer models. What a breakthrough.
    If the model calculated the nucleation rate correctly, they would have gotten to their result 10 orders of magnitude faster. 70 CPU seconds instead of 21 million CPU hours.
    That would be something to get excited about.

    • It’s progress. It may not be the greatest breakthrough in science ever. But it is progress.
      Everyone wants every paper to be a new Principia Mathematica. But sometimes papers are just a little way forward.
      This is a little way forward. That’s good.
      Why is there such scorn on this page today?

      • Keep in mind though, that although laudable, the goal of Principia Mathematica was impossible.

      • I’m with you on this. Too many people seem to come to this site with the “flame” button taped to the “on” position no matter the subject.

      • D.J. Hawkins,
        Maybe the problem is that too many people are too quick to see criticism as scorn and flaming?
        That said, there was a degree of scorn in my comment. It was directed not at the research, but at the hype.
        “The main significance of this work is to show that it is possible to calculate the nucleation rate for relatively accurate models of water,” said Haji-Akbari.
        Since that was done largely by sheer computing time, that is a pretty small increment of progress. If the main result was that now they know where the problem lies, and can start to fix it, I would be more impressed. They do allude to that: “The researchers were able to trace the discrepancy, which is 10 orders of magnitude, to aspects of the water model rather than to their method”, but that seems pretty vague.
        McCourtney,
        A little way forward is indeed good. But it should not be hyped as a breakthrough.

      • “Why is there such scorn on this page today?”
        The anti-sheep are a different color of sheep: “Two legs good, four legs bad.” Model==bad.
        The importance of discovering the speed of nucleation is not obvious; and yet I can see where it would matter to understanding of thunderstorms knowing how quickly phase changes can take place and thus the resulting rate of energy release or absorption. It sets a bound on the great heat engines of planet Earth. It is also known, but not widely known, that phase changes are not guaranteed at the usual temperatures and pressures.
        WUWT has from time to time interesting science reports that are just science reports, no politics explicit or implicit. That’s a bit unusual in the blog world where a typical blog always has a slant (DailyKOS, Salon, Huffington Post).
        What many see as a fatal flaw is really part of the validation cycle. Hypothesis, test, adjust hypothesis. In this case, model, compare with observation, adjust model. Once the model can reliably mimic observation then you can extend the model into temperatures and pressures not so easily observed. It’s still uncertain since you then need to validate at those other temperatures and pressures but at least it is a start where one can define a hypothesis.
        Many expensive scientific experiments exist to validate a model; the real work is in the model. The search for Dark Matter is such an exercise and so is the multi-billion-euro Large Hadron Collider. It exists to validate a model. Seriously? A billion euros to validate a model? Sure; because once validated that model can then help Efram invent Warp Speed (*) travel or prove once and for all it’s hopeless and all life on Earth is doomed.
        * https://en.wikipedia.org/wiki/Warp_drive

      • Well, like much of engineering, which is usually just a best fit because of the complexity and detail involved, and are just empirical rules that provide for an approximate and workable answer IF large safety factors are added in. This may provide some of the empiricism, but perhaps not so much basic understanding of what’s really going on. Basically, therefore, it’s hard to see the payoff considering the expensive input; but I guess they have to start somewhere.
        And this may be like a quote from physicist Tony Rothman which would indicate that although the field claims otherwise, is also basically empirical:
        “It would be surprising if the strange world of subatomic and quantum physics did not lead the field in mysteries, conceptual ambiguities and paradoxes, and it does not disappoint. The standard model of particle physics, for instance (the one containing all the quarks and gluons), has no fewer than 19 adjustable parameters, about 60 years after Enrico Fermi exclaimed, “With four parameters I can fit an elephant!” Suffice to say, “beauty” is a term not frequently applied to the standard model.”

  10. This is great, because it will allow more precise measurement of the Gore Effect (GE). How much more quickly and readily do ice crystals form, as the Goreacle approaches a given site at a given speed, for example?

  11. ” Debenedetti noted that the rate of ice formation obtained in their calculations is much lower than what had been found by experiment. However, the computer calculations are extremely sensitive, meaning that small changes in certain parameters of the water model have very large effects on the calculated rate. The researchers were able to trace the discrepancy, which is 10 orders of magnitude, to aspects of the water model rather than to their method. As the modeling of water molecules improves, the researchers may be able to refine their calculations of the rate.”

    Science:
    – compare model outputs to real world data,
    – refine, adjust model to minimize discrepancies.
    – repeat.
    Climate Pseudo-science:
    – compare data to politically useful model outputs,
    – refine, adjust, homogenize, infill, statistically torture the data to minimize discrepancies.
    – repeat.

  12. TonyL
    August 4, 2015 at 8:19 am
    Supersaturation wouldn’t be an issue with pure water. I wonder if a series of experiments simply using decrements of temp from zero and time to begin freezing and going to completion of the freezing for pure water wouldn’t give reasonable results for defining the process of phase change – without the crystal structures involved. Perhaps a clever way of setting up x-ray diffraction analysis while the process proceeds could be devised for determining the mix of cubic and hexagonal crystals. For water vapour – test a volume in a similar way with variation in concentration of water and temperature, first for pure water and then with various contents of aerosols commonly found in the atmosphere. The container of the apparatus presents boundary issues but if large enough, say a room-sized freezer unit some useful info should be obtainable. I would say the empirical work should precede any computer modelling.
    If you are modelling, you should also ensure you include deuterium. It’s about 150ppm of total hydrogen in natural water and heavy water has a freezing point near +4C. In addition to D2O you also get DHO which is intermediate in mass and freezes about +2C. They are both more viscous than H2O. Just with a simple thought experiment, it seems highly plausible that a framework of frozen D2O at 4C reinforced by a consolidation of the framework with DHO then freezing at 2C would create “cellular” water structure, restricting easy flow of H2O, setting it up for quick progression of freezing. Possibly we could detect this with x-ray diffraction and viscosity changes. I’m now thinking omission of D2O and DHO in climate modelling may also be a factor in confounding their simulations. Maybe now we will see a paper on this.
    Might using only H2O in the models be the reason for water freezing quicker than the models found? If they didn’t include D2O and DHO in their water model, then the those millions of CPU were essentially wasted. That they were 10 orders of magnitude off essentially makes it wasted anyway. Yeah, we have to overhaul the “education lite” that we have permitted to take over in higher education over the last 30-40yrs.

  13. Even if if it was correct, add the tiniest of impurities to the water and the problem becomes different again.
    That’s the problem with water. It hates computational chemists.

  14. Did anyone notice that this was at -43C, since when do you drop water moisture in to air at -43C?
    Surely the process starts way before that as the warm moist air rises, it must go through the atmosphere that is around +20 to + 30C down to -43C going through Zero on the way.
    Shouldn’t they be trying to find out how long it takes to remove the +20 to +30C after it the surrounding air goes below Zero?

    • A C Osborn,
      A pure drop of water, formed by condensation without any condensation nucleus (so no included solids) and suspended in air, can be cooled to somewhat below -40 C without freezing.

      • Yup.
        And have they even asked the question yet: “What is the solubility of CO2 in water at -40 C”?

      • “””””….. A phase change to ice releases heat. …..”””””
        Not so.
        Removal of heat results in the phase change (from liquid – solid, or gas – liquid).
        The phase change will not occur without the prior removal of the heat; that being the kinetic energy of jostling of the molecules that is stopping them from coming closer together to form the condensed phase.
        So don’t look to latent heat to warm anything. It must flow to a colder body in order to cause freezing.
        The order in which things happen is important; it tends to clarify which is cause, and which is effect.

    • A C Osborn writes “Shouldn’t they be trying to find out how long it takes to remove the +20 to +30C after it the surrounding air goes below Zero?”
      Yes they shouldn’t. “They” have a grant to do a specific thing.
      A phase change to ice releases heat. But in the immediate vicinity of the new ice nucleus that heat is immediately available to turn it back into water.
      So to seed a cloud, you find a way to separate that heat of fusion the instant a nuclei is formed, a lightweight molecule that easily absorbs the vibrational energy of the newly forming nuclei and does not just as quickly impart that energy right back to its source.
      One way to do that is with a molecule that itself has a property of phase change so that it can bind the energy and not give it up instantly. It can give it up, but must hold it long enough for the ice nuclei to stabilize at a large enough size that it is unaffected by surrounding energy.
      That (IMO) is why it matters how long it takes. It becomes a mechanical approach to cloud seeding. If ice needs a millionth of a second to nucleate, then you need something that can hold heat for 2 millionth’s of a second and viola, reliable nucleation of a cloud.

      • Good explanation. I was waiting for someone to show where the heat of transformation goes and why it goes there. Water is one of the rare molecules which has a very high energy release as it transforms from vapor – to – liquid – to – solid. High school physics told me that. But the details of the transition are important. If it were possible to release the energy fast enough and with enough molecules you could simulate a nuclear reaction. THAT would be really interesting!

    • Agree, but then we waste so much on the climate change budget which is circa $20+ billion every year with every agency getting and wasting their piece of the pie.
      Can anyone tell me what we have gained from the massive amount of $$$ over decades spent by the DOE or any technological breakthrough.
      wind and Solar don’t cut it and biofuels talk is in gallons not 100,000 of barrels.
      Fracking has produced orders of magnitude of energy without a subsidy.
      That’s the yardstick we should use to measure against.
      Private enterprise wins every time.

  15. To me this sounds like basic science being done…which is good. But you can just see other scientists using these methods and damn the inaccuracy.

  16. They would overlook the fact that by then welfare payments were vastly larger than the space exploration budget and produced nothing at all in return.
    Where is your DATA that “welfare payments ………..produced nothing at all……….”?

  17. Question to all , If you take a bucket of sea water say at 26 deg and add a bucket of ice it will freeze a can of soda why??? and do photons leave a contrail (Ice trail) like a hot jet engine does at height ???

  18. In order to properly model the ice formation, would they not need to already know precisely how ice forms to code it, thus negating the need for a model in the first place?

    • Let them go.
      They might eventually “discover” physical chemistry AND thermodynamics.

  19. With all the experts here, I have a question. Several times I have placed a cup of water in a microwave and set the timer to heat it up for coffee. However, I set in too much time. When I took out the water, on one occasion just touching the cup caused it to flash into boiling water and steam. On another occasion I had set it on the counter and the second that a few grains of instant coffee hit the water, the same thing happened. What causes this? Can the same sort of phenomenon occur by cooling water below the freezing point? Thanks in advance.

    • Well known phenomenon, I think a number of lawsuits have come from it. It’s pretty much the opposite of supercooled water.
      What’s happening is the surface of the cup has few scratches to hold things like tiny air bubbles, so for water to boil, not only does it have to fight the air pressure, it has to fight surface tension to begin to create a steam bubble. The grains of instant coffee (or freeze dried miso soup) trap some air, and as they get immersed in the water, the air bubbles provide a surface that steam can fill into without breaking the “surface tension barrier.” (Sort of like sound barrier, but different.)
      I first ran into this effect in high school chemistry, when the teacher asked me to boil down some ammonium nitrate solution to recover solid ammonium nitrate. I had a problem boiling it in a beaker because it would suddenly flash into steam splattering the solution around. I eventually discovered that if I took a glass stirring rod and touched it to a good spot on the beaker, I’d get a much better behave bubble stream from that.
      When the teacher came in to see how I was doing, he smiled and brought me a jar of “boiling beads”, pieces of ceramic that had lots of places to trap little air bubbles. They were meant to be used for exactly the problem I had.
      Once I found I could reproduce this in a microwave oven, I try to nuke a mug of water to just before it flash boils so I can watch it foam up as I put in the dried Miso soup mix. Sometimes I time it too well and a 2/3s full mug flashes enough steam to overflow. Just like it did in high school.

    • Well usurbrain; you need to usurbrain. Nuking clean water is a major no no, since it can heat so uniformly and contain NO nucleation centers.
      Excess (steam) pressure inside a bubble in boiling water is given by :
      delta p = 2 t / r where t is the surface tension of the water surface, in newton / meter and r is the bubble radius in metre (s).
      OOoops !! I see a problem there. If r starts out at zero, the delta p starts out at infinity.
      Ergo, sans a nucleus substrate, the water will super heat trying to make steam inside a bubble at an infinite pressure above ambient.
      If you then take it out of the nuculator, a dust mite will drop in the water and make a non zero radius substrate, and in serious cases the entire amount of water, can explosively vaporize instantaneously; and superheated stem in you face is not a good idea.
      So always add the nucleating material (coffee) to the water before nuking it.
      g

  20. This research, I bet, was funded by some gov agency. I also bet that this post-doc dude is foreigner. So, not only tax money were spent on nonsense research, but they also were spent on salary of non-US citizen.

  21. So we have earned that MODELS of water molecules can condense into MODELS is cubic ice and MODELS of hexagonal ice. What we still don’t know is how REAL water molecules can condense into REAL cubic ice and REAL hexagonal ice.
    Why?
    Because the condensation of REAL water releases REAL heat, which alters REAL pressure, both of which are statistical quantities requiring over thousands of trillions of real molecules (a number far beyond the capacity of even supercomputers to MODEL). It should be evident to any scientist that REAL pressure and REAL temperature changes will affect the crystal growth process.

  22. Even if no one else cares, I know that pilots and flight engineers are listening carefully.
    Ice accumulation on airplanes is something to be avoided.

  23. Problems of ONLY ten orders of magnitude, eh? That certainly qualifies for use and reporting by the IPCC then…

  24. Willis has been looking at Tropical CuNim as a governor. Take this a step further and take a deeper look at H2O phase changes in such clouds. What are the energetics in the upper reaches? We know all this conceptually however we don’t “know” this at the granular level. I think the key to understanding the mismatch between the climate models and reality is ice – the nature of the phase changes, where the changes are happening and the distribution of ice be it on land, as sea ice or in the atmosphere.

  25. Some years ago I observed plate ice crystals form almost instantly in the first poured jug of beer of the day [at the Gala Hotel in Kalgoorlie].
    There was no change in temperature, only pressure.

  26. Only TEN orders of magnitude?
    They’re taking the pish…aren’t they?
    Truly things really are worse than we thought!

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