From the INSTITUTE OF PHYSICAL CHEMISTRY OF THE POLISH ACADEMY OF SCIENCES
Evaporation for review — and with it global warming
The process of evaporation, one of the most widespread on our planet, takes place differently than we once thought – this has been shown by new computer simulations carried out at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. The discovery has far-reaching consequences for, among others, current global climate models, where a key role is played by evaporation of the oceans.
They all evaporate: oceans and seas, microdroplets of fuel in engines and the sweat on our own skin. For every one of us evaporation is of paramount importance: it shapes the climate of the planet, it affects the cost of car travel, and is one of the most important factors controlling the temperature of the human body. So common is it that it seemed that evaporation was a phenomenon that had been stripped of any more secrets. In the renowned scientific journalSoft Matter physicists from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, Poland, prove that this belief was erroneous and the mechanism of evaporation must operate differently than had previously been assumed.
“Science copes badly with descriptions of processes occurring in nature. We are perfectly able to describe the states at the beginning of the process and at its end. But what happens in between? How does the given process really take place? For so many years we have been asking ourselves this question in relation to the phenomenon of evaporation – and we are coming to ever more interesting conclusions,” says Prof. Robert Holyst (IPC PAS).
In scientific and technical deliberations we use the Hertz-Knudsen equation, known for over a hundred years, to describe the evaporation rate. What follows from it is quite an intuitive prediction: that at a given temperature the rate of evaporation of the liquid depends on how different the actual pressure at the surface is from the pressure which would be present if the evaporating liquid were to be in thermodynamic equilibrium with its environment.
“The further the system is from equilibrium, the more dynamically it should return to it. It’s so intuitive! So we checked the Hertz-Knudsen equation – because we like to check. In order to do this we prepared exceptionally accurate computer simulations which allowed us for the first time to take a closer look at the process of evaporation,” explains Dr. Marek Litniewski (IPC PAS).
Advanced computer simulations carried out using molecular dynamics showed that the values of some parameters describing evaporation are even several times larger than those predicted by the Hertz-Knudsen equation. However, an even more interesting effect was noted: the stream of gas being liberated from the surface of the liquid during evaporation changed very little despite significant fluctuations in pressure.
“There could only be one conclusion from this observation: the rate of evaporation and the vapour pressure, that is, the physical quantities that were previously considered to be closely related, were not so. For more than a century we had all been making a serious error in the theoretical description of the phenomenon of evaporation!,” says Dr. Litniewski.
The hitherto model of evaporation was based on the principle of conservation of mass: the mass of molecules released from the surface of a liquid had to respectively increase the mass of the gas in its surroundings. Physicists from the IPC PAS noticed, however, that since the particles released from the surface have a certain velocity, in order to describe this phenomenon what should be applied is the principle of conservation of momentum.
“We realized that to some extent evaporation resembles shooting from a cannon: the missile flies in one direction, but the overall momentum of the system must be maintained, so the gun recoils in the opposite direction. The same happens with the molecules of evaporating liquid. Since there is an increase in momentum, there must be recoil, and if there is recoil, the pressure felt by the molecules on the surface of the liquid will be different,” says Prof. Holyst.
The new computer simulations were also used to measure the velocities of the molecules released from the liquid surface. They proved to be small, of the order of hundreds of micrometres per second, which corresponds to only a few kilometres per hour. This fact means that practically any naturally occurring flow over the surface of the liquid has to strongly interfere with the evaporation process. The evaporation cannot thus be described by an equation derived for a very specific case, for liquid that is in thermodynamic equilibrium with the environment.
The discovery of the IPC PAS researchers is of the utmost importance for, among others, the understanding of the real mechanisms responsible for global warming. Contrary to common belief, the most abundant greenhouse gas in the atmosphere of our planet is not carbon dioxide but water vapour. At the same time, it is known that the speed of flow of air masses over the oceans can significantly exceed one hundred kilometres per hour and therefore they will certainly affect the rate of evaporation. The hitherto evaluation of the rate of evaporation of the oceans must therefore be subject to error, which will certainly affect the accuracy of the predictions of contemporary models of the Earth’s climate.
###
The researchers from the IPC PAS are investigating evaporation in collaboration with the Institute of Physics of the Polish Academy of Sciences in Warsaw, where experiments are being carried out to verify the correctness of the simulations.
CO2 was supposed to raise temperatures a little bit…
…which caused humidity to rise
It was run away global humidity that was supposed to do it.
When that didn’t happen…they realized that was probably the stupidest theory ever put forth in the history of mankind.
….and now CO2 is directly responsible for all of the temp increase.
And they are not one bit smarter.
(sound of palm smacking forehead…)
Hey Lat, you’d think if CO2 was causing warming, it would be showing up in the desert at night and be provable there. Excluding UHI and urban landscape humidification of course. Am I wrong here?
I think you’re spot on.
I’ve argued for years that CO2-induced warming should be extremely easy to spot at its claimed magnitude. It would be most apparent as a concentration-locked deviation in the time it takes for nighttime temps to stabilize in the middle of the driest desert you could find (this would include Antarctica).
We should already be at a half hour offset or more where the temperature should be detectably higher than it should be without the added CO2. In fact, this should make for a super-simple experiment in the lab. It doesn’t matter where the temperatures reach during the sunniest part of the day, at all, if it can cool all the way back down at night as if that extra CO2 was not there.
“We should already be at a half hour offset or more where the temperature should be detectably higher than it should be without the added CO2. In fact, this should make for a super-simple experiment in the lab. It doesn’t matter where the temperatures reach during the sunniest part of the day, at all, if it can cool all the way back down at night as if that extra CO2 was not there.”
Been there done that, ~78 million surface station records from the NCDC global summary of days data set, and then you compare daily warming to the following nights cooling, since 1940 cooling is slightly more, but at worst the average difference is 0.0F + / – 0.1F the uncertainty of the actual measurements.
..or in Antarctica where there’s no humidity
Remember, global warming was supposed to have the most effect at the poles
…and Antarctic temps have been going down since the very beginning
This fact means that practically any naturally occurring flow over the surface of the liquid has to strongly interfere with the evaporation process.
Good grief! That’s why we feel cold when wet with a wind blowing
Sorry – last bit of my post got lost
“Theoretical climate scientists and physicists discover what any practical engineer has known for 60 years, and are amazed.”
My thoughts exactly. Are we missing something?
Surely meteorologists must have a reasonably accurate idea of how much heat (and water) is transferred between the ocean and the air at various wind velocities. Anthony?
Do meteorologists (i.e. Pseudo Climate Scientists) have any idea at all how a sling Psychrometer (wet bulb hygrometer) works??? What do the teach in school today only digital and electronic instruments?
http://www.mie.utoronto.ca/labs/tkl/publications/RahimiWardKin.EvapSRT.pdf
Another paper, similar finding. The theoretical approach does not match observation.
Come on, – every meteorologist knows that evaporation is the opposite of condensation, and that latent heat is carried by the water molecules. If you have freezing water droplets in the atmosphere you get crystals of ice. The partial pressure of water vapor surrounding these crystals is lower than elsewhere, and new water molecules are attracted to the crystals. This is how snawflakes form. If evapration is the opposite process, then it obviously means that the partial pressure of water vapor is greater over an evaporation surface of liquid water than elsewhere. So this is what the Polish scientists have found out?
LOL. Meteorologists believe moist air is steam. Anthony too. Meteorology is dumb.
Martin Hovland:
Come on, – every meteorologist knows that evaporation is the opposite of condensation
Jim McGinn:
What meteorologists believe and what has actually been measured/tested (known) are two very, very different things. Condensation is also said to be the opposite of boiling. But boiling and evaporation are very different things. So . . . So it isn’t as simple as you suggest. Actually, nothing having to do with H2O in our atmosphere is a simple as meteorologists would have us believe.
Martin Hovland:
and that latent heat is carried by the water molecules.
Jim McGinn:
Why do you believe such silliness? There is no latent heat in evaporate. That is but a myth. Where is your evidence? Imagination?
Convective mass transfer vs. diffusion.
Do you think those are the only choices? Why? What else might we (or should we) consider?
Not strictly true. The amazement stems from the erstwhile inability to calculate/model evaporation not to the well known effect.
Yes, this is why you don’t try and model evaporation on a molecular level. You lose yourself in pointless details. Do it on the mass of the whole and your calculation can be pretty darn accurate. Any more accurate is pointless because of everything else that’s going on.
This is why engineering is objectively better than the “pure” sciences, because we can let go of things that don’t matter.
@Ben Klijn of Houston
+1000
Will this possibly lead to settling, once and for all, the age-old question of why ice is slippery?
I thought that was already settled. The pressure exerted by your boot/shoe causes micro-melting of the ice at the contact points. You actually slip on the water film thus formed. IIRC, if it’s cold enough outside you can’t ice skate because the pressure at the skate edge is not sufficient to cause melting at the low ambient temperatures.
And why snow squeaks as you step when it is really cold
I didn’t know snow squeaks in English. Maybe if you step on your shoe and forcibly turn it against snow in -20°C. I don’t know how I’d describe it if I just walk – maybe RRuck-RRuck-RRuck. Shudder. It’s soon here.
But hey, snow is a thing of the past.
Apparently it’s not quite settled.
http://lptms.u-psud.fr/membres/trizac/Ens/L3FIP/Ice.pdf
I can vouch for that. Below -15C it becomes difficult to skate on the canal in Ottawa. Mind you, I find it difficult to skate. And the wind chill effect of forward movement when skating can be considerable.
@ur momisugly Hugs:
Yes, it really does squeak. It gets really cold, and it goes way past RRuck-RRuck, and then scrunch, and then squeak, squeak. Now you know it is really cold. So we would grab our skis and head for lift, knowing it is colder still, up top. We thought it was all great fun. What on Earth was wrong with us?
@Hugs: snow does squeak underfoot at very low temperatures. I’ve heard it myself with just walking forward, no sideways motion with the feet, at -5°F (-20.5°C).
Was squeaking snow really in question and not sarcasm?
I guess I’ve spent far to much of my life in cold weather, and not enough someplace warm where there isn’t any snow, let alone squeaking snow!
For side interest, a small sheet of bismuth metal also squeaks when gently flexed. First heard it with a piece the shape of a biscuit (cookie) between opposite hands. Noise does not seem to get less if you flex for a long time.
(One main use for bismuth is in France, in medicines to counter indigestion. While bismuth has little to do with cold ice and climate, one can speculate what else would make a noisy objection to being swallowed by a French person. Frogs?)
how about the question of why warm water freezes quicker than cold water?
Please tell me you are kidding!
I’m afraid it’s true, at least under some conditions. What a strange substance!
http://arxiv.org/ftp/arxiv/papers/1310/1310.6514.pdf
I have found quite a few articles regarding explanations about the Mpemba effect, but all the ones I found weren’t as certain as you seem to be, menicholas.
http://interestingengineering.com/why-hot-water-freezes-faster-than-cold-water/
The explanation that I heard for warm water freezing faster than the same initial amount of cooler water is that the higher kinetic energy of the warmer water molecules escape the surface in larger quantities thereby leaving a smaller amount of water behind than the cooler water. This smaller amount of water then freezes more quickly because it is a smaller amount. Yikes! is this really true? By adding more energy to a system we can more quickly cool it? Well, I guess this happens inside of refrigerators and freezers, but that’s different.
@ur momisugly David Ball:
Mpemba Effect was likely a hoax. It had quite a lengthy Wikipedia entry, I checked about a year ago, no entry.
Anyway: Everybody Listen up.
Colligative Properties: Boiling point elevation and Freezing Point Depression.
You boil water, you drive off the dissolved gasses, raising the FP up to where it should be. Water loaded with dissolved gasses has TWO factors inhibiting freezing:
1) The FP is lower
2) The gas molecules interfere with water crystal formation, slowing the kinetics.
If you want to finesse an experiment, set a freezer at -2.0 deg C. Just below freezing. Boiling water will cool rapidly, then smoothly freeze. Cold water, loaded with gasses, will just sit there like it has no idea it should not be liquid anymore.
If they have all kinds of explanations, and experiments are not reproducible, or lots of strange things happen, then they really do not have an idea of what is going on. Like climate, for instance.
Here’s one experiment for testing the role of dissolved gasses in this question:
Take 4 identical containers A, B, C, D each with the same amount of water. Enclose two of them, A & B, with lids. Leave C & D open. Put A & C in an oven and heat to a very low temperature so as not to explode A. Put all 4 containers in a freezer and record the times for each to freeze.
I’ve seen this theory before, but no one has been able to explain this: if the warmer water is cooling faster, as it must if it is to feeze first, then at some point both samples are at the same temperature. At that point, what is the difference between the two samples? Are you suggesting that the previously warmer water has some ‘memory’ of having started warmer and is responding to it? I think an adequately controlled experiment would show this theory to be a myth.
Seaice:
Nitrogen (N2), has a molecular mass of 28, O2 has mass 32. Water (H20) has mass 18. If you replace some N2 or O2 with H20, it will weigh less for the same number of molecules.
Jim McGinn:
Moist air at ambient temps ALWAYS weighs more than dry air. Water is NOT an ideal gas. Weight of H2O is 18 x X; X being 10 or larger. Thus 180 is the lightest possible.
See other post on this thread for details as to why moist air rises–it has nothing to do with convection. Convection is but a product of meteorological stupidity.
@ur momisugly David Ball:
Mpemba Effect was likely a hoax. It had quite a lengthy Wikipedia entry, I checked about a year ago, no entry.
Jim McGinn:
It’s not a Hoax. But a lot of details are being left out here. Mpemba was a culinary student from Kenya who was learning to make ice cream.
Look into non-Newtonian fluids.
H2O polarity, hydrogen bonding are implications. Another example is corn starch and water that “freezes” when pressure is applied.
Meteorology is permanently confused about the role of H2O in our atmosphere.
Another one is superchilled water.
noaaprogrammer:
The explanation that I heard for warm water freezing faster than the same initial amount of cooler water is that the higher kinetic energy of the warmer water molecules escape the surface in larger quantities thereby leaving a smaller amount of water behind than the cooler water. This smaller amount of water then freezes more quickly because it is a smaller amount. Yikes! is this really true?
Jim McGinn:
No, it’s not true. The correct explanation is very complex. It depends on understanding the dynamics underlying H2O polarity, hydrogen bonding, and implications. I can explain it but I would first have to educate you and that would be difficult because you’d have to get rid of a lot of misconceptions that meteorology has been feeding you.
When it comes to H2O in the atmosophere almost everything meteorologists have been telling you is wrong.
Jim McGinn,
Do you have an answer for Jtom? I’m curious about it. He said:
if the warmer water is cooling faster, as it must if it is to freeze first, then at some point both samples are at the same temperature. At that point, what is the difference between the two samples? Are you suggesting that the previously warmer water has some ‘memory’ of having started warmer and is responding to it?
How about an elevator speech explaining it?
While you’re at it, there must be more to your other reply than this:
Convection is but a product of meteorological stupidity.
Pretend I’m stupid. Could I create convection?
Or, are you trying to claim that convection doesn’t exist?
Jim McGinn,
Do you have an answer for Jtom? I’m curious about it. He said:
Not now.
Convection is but a product of meteorological stupidity.Pretend I’m stupid. Could I create convection? Or, are you trying to claim that convection doesn’t exist?
http://t.co/BUKr9dnK9O
http://t.co/BUKr9dnK9O
dbstealey October 28, 2015 at 7:50 pm
Jim McGinn, do you have an answer for Jtom? I’m curious about it. He said:
if the warmer water is cooling faster, as it must if it is to freeze first, then at some point both samples are at the same temperature. At that point, what is the difference between the two samples? Are you suggesting that the previously warmer water has some ‘memory’ of having started warmer and is responding to it?
How about an elevator speech explaining it?
Jim McGinn:
Okay, fair enough. I put it out there, I should be willing to defend it. Hmm. How about I drop you a link for now:
Why Water is Weird
http://wp.me/p4JijN-49C
(also, scroll down for more links on that webpage)
While you’re at it, there must be more to your other reply than this:
Convection is but a product of meteorological stupidity.
Pretend I’m stupid. Could I create convection?
Or, are you trying to claim that convection doesn’t exist?
Essentially, yes. It doesn’t play much of any role in earth’s atmosphere.
@J. McGinn,
That reply does nothing to answer Jtom’s question.
That should have been done *before* publishing the study.
Mike — good point — Eugene WR Gallun
Exactly so but in this age where career progression is so dependent on frequency of publications it is not in the least uncommon. Incidentally, this effect is seen in other parts of the climate debate. Not least where there is a rush to announce this and that and not research the fact that the models do not work even when we are in an unexpected temperature pause.
Interesting point you raise there- when should you publish results? In this case the result is interesting enough to be worth getting out to a wider audience of peers (scientists in your field), since whether or not the experiments reproduce the predicted result, it will leave questions requiring answers. If the theoretical model fails, then we need to know that so we can improve the model. If it succeeds, then we need to know that so we can include the improved model in our future predictions.
However, I wholheartedly agree that the press release is premature, and should have waited for confirmation or otherwise.
Always beware press releases. they are often used to make claims that cannot be substantiated by teh actual paper. Cold fusion springs to mind. Go look at the original paper to see what it really says, and you can usually rely in that not to make claims totally out of proportion to the facts.
I used to work in the U.S. Bureau of Reclamation programming a simulation of the water system for the (then) proposed Jordanelle Dam on the Provo River. The simulation took into account evaporation rates on Deer Creek Reservoir and Utah Lake. The rates were calculated by experiment if I remember it correctly, not by use of simulations. Mike here has implied the question “why didn’t they check the simulations against observation?”
I want to know what is wrong with “scientists?” these days. Science is about using all of the scientific method, not half of it. These guys are publishing the equivalent of a hypothesis generated by simulation but advertising it as if it were a conclusion. You don’t get conclusions until you verify that what the simulation says happens actually happens in reality. They talk about their calculations as being extremely accurate and precise. That is all very poor and bad since they can’t know if it is accurate or precise until they can match it up with observational data from the real world.
It seems as if their “science?” is more about feelings and simulation than facts. They just “know” it has to be right.
Exactly Jeff. Science has completely lost it’s ‘mojo’. As retired scientist I have lost all respect for science and my old institution Inst of Physics
Theoreticians have always hated empiricists, it’s a feud that goes back to the origins of science and beyond. No teller of tall tails appreciates some “person of limited imagination” sayin’ it just ain’t so.
Two words: “evaporation pans”.
+1. Computer models without empirical verification of their predictions are merely computer models without empirical verification of their predictions.
“Computer models without empirical verification of their predictions are merely”…a neat collection of ones & zeros.
The modeling step gets so much easier if you don’t have to verify the output against reality.
I think you meant to say – ‘Computer models without empirical verification of their predictions’ … form the basis of climate science. 🙂
“Computer models without empirical verification of their predictions” … allows the designer/user ignore reality and to massage the input & theoretical corrections in a manner that results in users’ desired data output.
Computer models without empirical verification allow publication with getting your hands dirty or having to face the challenges of designing and constructing any apparatus. Any weenie can model, it takes some brilliance to design, for example, an oil drop experiment.
From a comment in the post ‘Lucia has a bad day with partial derivatives’ by Dr David Evans over at Joanne Nova’s site:
Verification?
We no need no stinking verification!
Look who’s talking. The same guy that says moist air is lighter than dry air despite never having verified it. Moist air rises at the equator. It has nothing to do with convection because moist air is heavier. Believers believe. Scientist measure. What is your excuse?
I’m intrigued that, apparently, these models are OK for the WUWT commenters to draw all sorts of conclusions, while the IPCC models are junk. Yet, these models were also unverified at the time of the rush to publication. Maybe the results are wrong, also?
Good point. WUWT is run by a meteorologists. Meteorologists never test anything.
NOW you will test it?
Absolute nonsense.
The uncertainty in measurement and grid cell averaging of the wind field will far outweigh this mini adjustment ( should it turn out to be verified by experiment).
I certainly don’t see this affecting AGW theory since the whole thing is a mess in terms of modelling evaporation, cloud formation and precipitation, this tweak will not make an iota of difference to their problems.
What is will do provide a +1 for next Cook et al try to Cook the books and publish false claims. This paper will be classed as a work that implicitly endorses AGW.
Mike, it IS nonsense.
Climate is the aggregate of daily weather averaged over multiple years. Likewise, future climate at a specific future year is the aggregate of the daily weather averaged over multiple future years just prior to the predicted year. It seems to me that if these statements are true, wouldn’t they need to accurately predict the daily weather for those multiple years? We can’t even predict weather more than a few days in advance let alone 50, 85 or 100 years. Most, if not all, the models failed to predict the current flat temperatures of the last 18 years despite new record CO2 emissions every year during that time.
So, for a moment, lets pretend CO2 was the cause of warming. I don’t think it is since water vapor swamps out CO2, but this is just pretend time, ok? That would mean some other process is holding the temperatures down. We AND the alarmists don’t know why. If we or they don’t know why, then no one really knows enough about atmospheric systems to predict warming or cooling for any time in the near or far future at present.
As financial services are required to say: “past performance is not indicative of future results.” So even if they torture past data to “predict” current climate, it still doesn’t mean anything for the future. Which means all the blather we hear about future climate is really purposed to changing political weather in favor of reduced freedoms and increased government control, a bureaucrat’s dream come true.
Not really, in electronics timing verification you can describe an input less set of conditions that determines the min and max data path timing, something like this could be done if we understood the climate, then if you could determine a distribution of weather you could generate a measure of climate with out know the weather. In fact this is what they attempt with their ensembles. This solves some of the computational limits of running weather simulations.
Doing climate models like this would likely take decades, as with our limited understanding of weather, we would need to create many variants of this type of model, run them into the future, and then I believe you’d have to wait for decades to see which ones had good results. Now genetic evolution of models might be better at this, but I don’t see how you could skip comparing results to future measured climate.
“Climate is the aggregate of daily weather averaged over multiple years. Likewise, future climate at a specific future year is the aggregate of the daily weather averaged over multiple future years just prior to the predicted year. It seems to me that if these statements are true, wouldn’t they need to accurately predict the daily weather for those multiple years?”
Not really, #2:
To know the climate, one needs to know the range of temperatures and precipitation amounts that occur during a given season in a given area. To predict the weather, one must predict the Temp. and Precip. on a particular day.
Not saying I agree with any climate predictions, though.
SR
The paper is about the micro effects at the surface, in the case of a wind field this would be inside the boundary layer. Making measurements at this scale is very difficult, I would think some very fine scale laser techniques would be necessary, eliminating airflow near the surface and solubility of gas in the water wouldn’t be trivial either. Reminiscent of ‘polywater’ in the 70s.
They still need to apply the conservation of mass. My impression from reading the press release is that this either not correctly reported or is a mistake that will be retracted once they try to verify it.
But water vapor/surface process greatly effect surface temps, evaporation as described, and conversely high rel humidity as water condenses out of the air at night slows radiative heat loss (watch the nightly cooling rate, and how it slow at high rel humidity for proof).
Moist air is less dense than dry air, evaporation decreases the air pressure above the water. The moist air rises and is replaced by cooler drier air and the cycle begins. Wind decreases the air pressure over the water due to the Bernoulli effect. Lower pressure increases the rate of evaporation.
The relative humidity can stay the same, but there is massive non radiative cooling occurring at the same time.
“Moist air is less dense than dry air” Thsi is somewhat counter-intuitive, but true (atthe same temperature). Nitrogen (N2), has a molecular mass of 28, O2 has mass 32. Water (H20) has mass 18. If you replace some N2 or O2 with H20, it will weigh less for the same number of molecules. The key insight is that a given volume of any (ideal) gas contains the same number of molecules.
However, if the water condenses into droplets of liquid, these will be much more dense than the gas. Air containing water droplets may be more dense than humid air containing water only as only vapor.
Seaice:
Nitrogen (N2), has a molecular mass of 28, O2 has mass 32. Water (H20) has mass 18. If you replace some N2 or O2 with H20, it will weigh less for the same number of molecules.
Jim McGinn:
Moist air at ambient temps ALWAYS weighs more than dry air. Water is NOT an ideal gas. Weight of H2O is 18 x X; X being 10 or larger. Thus 180 is the lightest possible.
See other post on this thread for details as to why moist air rises–it has nothing to do with convection. Convection is but a product of meteorological stupidity.
Jinghis:
Moist air is less dense than dry air,
Jim McGinn:
Less dense in what respect? The myth is that moist air is lighter (weight not density) than dry air. The myth is just that, a myth. Moist air is heavier than dry air. Meteorology maintains this myth so that their poorly considered storm theory models are not revealed as the complete nonsense that they actually are.
Jinghis:
evaporation decreases the air pressure above the water.
Jim McGinn:
Low pressure tends to travel down (from jet streams) and into (and through) moist air. Being heavier, moist air has negative buoyancy. Moist air rises because it is a target of low pressure from above, thus it rises. But it has nothing to do with convection. Convection notions are but poorly considered myths from a paradigm that refuse to test and measure. Meteorology has a lot of bad thinking.
Don’t add to the bad thinking of meteorology. Insist that they measure the weight of moist/dry air.
Lets force meteorology to do real science and stop pretending.
Science is built on facts. Not imagination.
Meteorology is not science.
The “correctness” of the simulation can be observed in any of hundreds of industrial wet process & HVAC cooling towers.
As Leo observed, practicing engineers (me) dealing with reality learned the characteristics and power of water vapor every day and long ago.
The researchers were performing numerical experiments on the molecular scale. Atmospheric models have no hope resolving scales that fine, so they resort to “bulk” parameterizations. Unless those parameterizations are shown to be in error, this won’t affect any model results.
Last few lines say they are actually doing physical experiments to generate data to verify the computer simulation? NO! NO! This can’t be climate science! — unless they intend on calling in Gavin Schmidt to adjust the data.
Eugene WR Gallun.
OH man, that’s always a good sign that someone is not thinking. It part of the “I must be right, what else could it be?” school of modern science.
Let me help them by providing just ONE other possible conclusion: YOUR MODEL MAY BE WRONG.
Just a thought
Does this mean that our equations describing how much ocean water a 200 miles-per-hour hurricane evaporates were not entirely precise?
This is basis of their error, I think. The molecules that escape are statistical outliers that manage to break free. The recoil is already there in the statistical distribution of the momenta of the remaining molecules. If they are adding an extra term to account for the “recoil” the model is probably wrong.
Conservation of mass can’t be wrong so if they see a conflict they are making a mistake.
Psy krwi, Leave it to the Poles, gówno, don’t they know the “Séance is settled”?
michael
Well I might even accept their description of how a single molecule of H2O gets fired from a cannon, hiding in the surface. I always thought that it was some sort of Van der Waals forces that kept the molecules attracted to each other, which results in the surface tension at the surface, because the molecules that were supposed to be pulling from above just aren’t there, so there is a net downward, surface contracting force.
When some tail end Charlie molecule, that has a KE way out on the high energy tail of the M-B distribution, finally breaks free, then you would expect that the force which had been pulling it downward, would get distributed somewhere else.
But at the Equilibrium evaporation rate; if it makes any sense to call that equilibrium; for every H2O molecule able to break away, there is another molecule in the adjoining gas phase, that has obtained a net momentum towards the liquid surface, from collisions with other atmospheric molecules, and that causes it to impinge on the surface, and get grabbed by what ever that force was that got severed in the previous escape.
So you have the typical dynamic equilibrium situation, which is really more of a steady state condition, than an equilibrium.
But as far as the evaporation rate is concerned; as every chemical process engineer knows (IANACPE) it is the removal of the escaping species from the scene, that determines if the evaporation will proceed.
The dynamic steady state, depends on the number of arriving molecules equaling the number of leaving molecules (on average, as they say).
So of course things like surface wind speeds, that whisk the exiting molecules off to some place, they can’t get back from, is the crucial thing in evaporation rates.
Well maybe their compotator gives them a different explanation.
But so what.
Global warming climate change does not rest on the dynamics of exit molecule removal.
It’s a closed loop feedback system, that balances cloud formation blocking solar energy, with thermal processes affecting the Temperature including the evaporation of water bodies.
The question they need to ask their computer, is how much does the total cloud cover change, for a given delta in their surface wind speed, with the whole feedback loop operational.
So what changes in experimentally measured evaporation rates, have been unearthed as a result of this discovery, and why were they previously unknown ??
Surely people have been measuring evaporation rates under varying conditions for eons.
g
George E. Smith October 22, 2015 at 10:09 am
Well I might even accept their description of how a single molecule of H2O gets fired from a cannon, hiding in the surface. I always thought that it was some sort of Van der Waals forces that kept the molecules attracted to each other, which results in the surface tension at the surface, because the molecules that were supposed to be pulling from above just aren’t there, so there is a net downward, surface contracting force.
When some tail end Charlie molecule, that has a KE way out on the high energy tail of the M-B distribution, finally breaks free, then you would expect that the force which had been pulling it downward, would get distributed somewhere else.
But at the Equilibrium evaporation rate; if it makes any sense to call that equilibrium; for every H2O molecule able to break away, there is another molecule in the adjoining gas phase, that has obtained a net momentum towards the liquid surface, from collisions with other atmospheric molecules, and that causes it to impinge on the surface, and get grabbed by what ever that force was that got severed in the previous escape.
Absolutely George, if you started out far from equilibrium then initially you have a net exchange but as equilibrium there’s a balance of ‘leaving molecules’ and ‘entering molecules’ as you say. By the way, in the case of water it’s ‘Hydrogen bonding’ which provides the attraction in the liquid phase which is much stronger than van der Waals, this is what gives water it’s unusual properties (compared with say hydrocarbon liquids which only have the van der Waals).
Thanx Phil; you notice I said ” some sort of Van der Waals forces ” because although I have heard of them; I really have no fundamental understanding of exactly what VdW forces really are; I just learned of their existence at some very primitive level in a physics course, not a chemistry one, and that was about 60 years ago.
And as for ‘Hydrogen bonding’, that is much more recently invading my mental space, and I still don’t have what I consider a good grasp of the concept.
But water sure is weird stuff ! It’s dielectric constant of about 81, gives it apparently some of its chemical properties, because electrostatic forces should be reduced by that factor, between electric charges in water (presumable good DI (18 megohm)) water.
g
Since it tends to be the higher energy molecules in the distribution, that escape the binding forces of the liquid, the result is a net lowering of the energy content of the liquid, so it cools.
I have no idea how much of the latent heat of evaporation is simply due to the loss of the high end of the energy distribution. Maybe that is all of it.
I haven’t plotted an M_B energy distribution in many blue moons, but imagine that molecular KEs of several times the most probable molecule energy, are rather numerous, and the most likely to evaporate.
So the average energy per molecule, being lost in evaporation could be a sizeable amount, so it wouldn’t surprise me, if that is the sum total of the latent heat of evaporation or sublimation.
The latent heat of evaporation of water is about six times the heat required to heat ice water to the boiling point. Which is why steam burns are extremely dangerous.
g
Hmm, sceptics should be consistent, just because scientists link their work to global warming, that don’t make it so, maybe they try linking it to the evaporation models used in meteorology.
When that H2O molecule leaves the surface it takes 970.4 Btu/lb, 284 Wh/lb, with it as well as lowering the dry bulb. Recall the cooling aftermath of a summer rain storm.
Consider the psychrometric properties of moist air. Water evaporates into the air because the air is relatively dry, not necessarily because the air is warm.
With time and turbulence and contact evaporating water vapor can saturate any temperature of air. Frosty breath on a cold morning is saturated vapor.
Nick, the latent heat depends on temperature. Check if your numbers are correct for a boiling point or for a freezing point.
Latent heat does not vary very much with temperature. Heat of vaporisation of water reduces by about 10% from 10°C to 100°C. At 25°C it is 44 kJ/ mol, or 2444 kJ/kg.
Hey there, Nicholas:
As it happens, evaporation does depend to a certain degree upon temperature, at least out in the wild: “surface level” air below about -40F (or C, hehe) can’t physically hold much water vapor in suspension (let alone coax it out of standing water… if you can find any!), and I’ve seen your example of ‘frosty’ breath at temps of ~ 80F in places like Bahrain where the ambient moisture is already thick enough that one’s breath pushes it past the point of condensation.
For the record, that was a weird experience: fog should not happen at 80F on a desert island, it’s unnatural. ^_~
Perhaps Anthony could get into the habit of providing refs rather than just doing copy/paste from UreaAlert. , since he is always dissing other for not providing refs.
The line following the end of the bit Anthony copied here, contains a link to the institute which has a direct link to download the full PDF paper:
Molecular dynamics test of the Hertz-Knudsen equation for evaporating liquids”; R. Hołyst, M. Litniewski, D. Jakubczyk; Soft Matter,
2015, 11, 7201-7206; DOI: 10.1039/C5SM01508A
http://ichf.edu.pl/press/2015/10/IChF151022a_PL.pdf
oops wrong like for the paper. But at least the DOI.
For those who want to dig:
SI http://www.rsc.org/suppdata/c5/sm/c5sm01508a/c5sm01508a1.pdf
http://pubs.rsc.org/en/Content/ArticleLanding/2015/SM/C5SM01508A#!divAbstract
The boiling point is a guide to evaporation. Here is a discussion of the boiling point(s):
http://www.ucl.ac.uk/sts/staff/chang/boiling/index.htm#5
The contents of the water and air are not the only things that promote evaporation. I vote that there are molecules on the surface that serve as nucleation sites which ‘launch’ the H2O molecules and that the mooted recoil is not present or is minor, and certainly not the only mechanism. The ‘pure water’ assumption is that energy from six molecules launches the one they surround. Well, sea water isn’t like that. It is chock-a-block with other polar molecules, large and small.
As has been demonstrated many times, evaporation of pure water can be delayed to a temperature as high as 200 C. Whatever bouncy-ball physics they are simulating, molecular evaporation catalysts should not be ignored as a major or dominant pathway.
I also recall a recent study ( 2 or 3 year ago) suggesting that ocean surface often displayed liquid crystal like properties.
They are a universe away from anything to do with ocean water in their simplistic billard ball models. But one can always rely on use of AGW to grab some attention. It got them onto UreaAlert anyway.
More money is needed to study the importance of this effect on climate change ……. blah, blah, blah.
My buddy’s thesis advisor told us about that. Naturally, we had to try the experiment. I can tell you that God exists and protects young males because, otherwise, none of us would still be alive. (ie. when the water finally boils, it does so explosively)
“As has been demonstrated many times, evaporation of pure water can be delayed to a temperature as high as 200 C.” I have seen pure water heated above its boiling point and not boil due to lack of nucleation sites for gas to form, but never anywhere near 200°C. At this temperature I was only aware of maintaining liquid by applying pressure -about 15 bar will keep water liquid at 200°C. I was very interested to learn from your link that Krebs had achieved 200°C without boiling by suspending water in other liquids and then heating.
However, whatever the mechanism of the “launch”, conservation of momentum still requires that there be recoil.
As pointed out by George (above) there are also incoming molecules, also conservation of mass, momentum, and energy must apply, entropy effects could also be important.
Perhaps we are missing the point.
CAGW as an operational meme has run its course.
“Studies” such as this serve a different purpose.
The great glibbering climb down.
Our Models were perfect, science had it wrong about water and all its nasty habits.
Evaporation?Who knew!
CAGW right , bad science.
AKA Not our fault, nothing to see here, move along.
Next study will express amazement that we live on a world dominated by water.
I’ll be optimistic and assume they will be doing experiments in the real world, outside of a computer simulation. If the verification of the model simulations are other model simulations, then it’s the scientific equivalent of movie CGI; fun to look at, but not to be confused with reality.
The system is unwieldy to model/estimate, insufficiently and incompletely characterized, and conclusions are derived through inference. Not exactly a scientific enterprise.
And trillions of dollars in redistributive change. Perhaps it’s a cult.
Let’s see, they say –
The further the system is from equilibrium, the more dynamically it should return to it. It’s so intuitive! So we checked the Hertz-Knudsen equation – because we like to check. In order to do this we prepared exceptionally accurate computer simulations which allowed us for the first time to take a closer look at the process of evaporation,” explains Dr. Marek Litniewski (IPC PAS).
If they were basing their research in standard theory, then, things wouldn’t be different. But they developed “exceptionally accurate computer simulations” to prove or disprove. Based on WHAT? Either it is based in the reality of what they know – you can’t model what you don’t know – or they created something based on their conceived beliefs. If is an actual simulation, even exceptionally accurate, it will prove what it is modeled on, not what it is not modeled on, and this has been my biggest beef about “climate crisis workers,” I can’t call them scientists, and that is that they can’t realize that their models and/or simulations can’t tell them anything but what they want to see, and it can’t project with any accuracy the reality of climate since they do NOT know climate to start with.
Well.. but … there’s no sport in a stationary target such as ~only~ aerosols or ~only~ heat hiding in the ocean and besides, they’re being paid to keep the excuses coming anyway. Once the pigeon flies there’s no time to complain about it – you only get that one chance to shoot at it!