Can you keep an open mind on the cause of winds? Climate science needs your help!
by Anastassia Makarieva
Many of us who have become researchers have been attracted by the dynamic and constructive debate that lies at the heart of scientific progress. Every theory is provisional waiting to be improved or replaced by a more thorough understanding. In this perspective new ideas are the life-blood of progress and are welcomed and examined eagerly by all concerned. That’s what we believed and were inspired by. Is climate science a dynamic field of research that welcomes new ideas? We hope so – though our faith is currently being tested.
Five months have not been enough to find two representatives of the climate science community who would be willing to act as referees and publicly evaluate a new theory of winds. Of the ten experts requested to act as referees only one accepted. This slow and uncertain progress has caused the Editors to become concerned: recently they “indefinitely extended” the public discussion of the submitted manuscript. The review process is perhaps becoming the story.
Here the authors share their views and request help.
Background
On August 06 2010 our paper “Where do winds come from? A new theory on how water vapor condensation influences atmospheric pressure and dynamics” was submitted to the Atmospheric Chemistry and Physics Discussions (ACPD) journal of the European Geosciences Union. There we proposed a new mechanism for wind generation based on pressure gradients produced by the condensation of water vapor. ACPD ensures transparency during the review procedure: the submitted manuscripts and subsequent reviews are published online and available for public discussion. Authors can follow their submission through the process: they see when the Editor invites referees and whether they accept or decline.
Here are the standings as of 20 January 2011:
The Editor handling our paper has invited ten referees so far. Only one, Dr. Judith Curry, accepted. After 10 November 2010, in the record there have been no further attempts to find referees.
Normally ACPD’s discussion should take eight weeks. But in early January 2011, after twelve weeks in process, the status of the discussion of our manuscript was changed to “indefinitely extended”. In a recent letter to the authors, the Editor-in-Chief admitted that handling ‘a controversial paper’ is not easy, but assured us that the Journal is doing their best.
Discussion of our propositions secured over a thousand comments in the blogosphere within four weeks of publication indicating wide interest. Among the ACPD discussion participants two are active bloggers. Does blog culture outcompete formal peer review in evaluating novel concepts? It’s an open question. But let’s take a moment to focus on science.
Why condensation-induced dynamics is important
It would be generally useful to understand why the winds blow. It is sufficient to note that understanding the physical bases of atmospheric circulation is key for determining the climate sensitivity to changes in the amounts of atmospheric greenhouse substances, which is currently a highly controversial topic. The lack of current understanding may not be widely recognized outside the climate and meteorological community. But within the community moist processes in the atmosphere are admitted to be among the least understood and associated with greatest challenges. Not only theorists, but also modelers recognize their existence. For example, in a paper titled “The real holes in climate science” Schiermeier (2010) identified the inability to adequately explain precipitation patterns as one of such holes. In particular,
“a main weakness of the[ir] models is their limited ability to simulate vertical air movement, such as convection in the tropics that lifts humid air into the atmosphere.”
Any meteorological textbook will provide a discussion of buoyancy-based convection: how a warm air parcel ascends being lighter than the surrounding air. The convective instability of moist saturated air, so far neglected by the meteorological theory, is different. Any upward displacement of a saturated air volume, even a random fluctuation, leads to cooling. This causes the water vapour to condense. Condensation diminishes the total amount of gas and thus disrupts the hydrostatic distribution of moist air (if a hydrostatic equilibrium exists it is unstable to any such minor movements). The conclusion: moist saturated atmosphere in the gravitational field cannot be static.
Our analyses show that the current understanding of air movements being dominated by temperature and buoyancy is incomplete and flawed. Rather we find that the phase changes of water (condensation and evaporation) can play a much larger role than has previously been recognized. You can find out more if you see our paper. We would hope that a dynamic and advancing science would welcome new ideas.
Can the blogosphere help?
Perhaps we can help the Journal review our paper with your help. Are you an open minded climate scientist who would be ready and competent to discuss our ideas?
The ACP Chief-Executive Editor Dr. Ulrich Pöschl is aware that we are inviting your helps and asked that the following issues be noted (we quote):
1) ACPD is not a blog but a scientific discussion forum for the exchange of substantial scientific comments by scientific experts.
2) The open call for scientific experts who would be ready to act as potential referees would be a private initiative of the manuscript authors.
3) The list of potential referees compiled by the authors will be treated like the suggestions for potential referees regularly requested. The responsibility and authority for selecting and appointing referees rests exclusively with the editor.
If you have no conflict of interests and are willing to review our paper please contact the corresponding author (A. Makarieva) and we will forward your details to the Editor as a potential referee. For those who would like to remain anonymous please approach the ACP Chief-Executive Editor directly. We would be very grateful for your help – we have faith in you.
Anastassia Makarieva
on behalf of the authors:
A.M. Makarieva, V.G. Gorshkov, D. Sheil, A.D. Nobre, B.-L. Li
P.S. Thanks to Jeff for hosting our appeal on this blog. For a list of publications relevant to condensation-induced dynamics, please, see here.
wayne & steve;
you’re both trying to imagine what happens, and failing. 100% of the latent heat is transferred to the surrounding molecules. A window pane that condenses water vapour is warmed by that process. Air temperature cannot drop below the “Dew point” because condensing the dew dumps heat into the air, until humidity is lowered to the point that the dew point also drops. And so on.
Real heat is required to evaporate water (which is why sweat succeeds in cooling your skin). And condensing it releases all that heat again.
Steve,
I agree with your description beginning “I’m a visual thinker.” Furthermore, I can perfectly see how “I took that to mean that as warm air rises you suddenly get a burst of positive pressure”.
But what I meant was that adiabatic expansion of dry air from V1 to V2 where V2 > V1 gives a greater pressure drop than adiabatic expansion of moist air. The latent heat causes the air molecules around the water droplets to buzz around more rapidly.
If we have a 1-km wide body of air, we can imagine that the heat transferred by mixing, conduction, and radiation across the boundaries of the body will be negligible compared to the work done by the gas in expanding and rising. I assume you agree with that. If so, then you’ll see that the ideal adiabatic expansion equation is useful in understanding how the gas cools as it rises.
We can arrive at the effect of latent heat upon the gas in several ways, and one of the simplest is to imagine the gas expanding adiabatically (no heat transferred by conduction, mixing, or radiation) to a certain volume and pressure, and then we calculate the effect of condensation upon the pressure, even though we know that this condensation would occur during the expansion, not at the end. The net effect is positive: condensation raises the pressure compared to that of dry air.
In Anastassia’s paper, it seems to me (and recall that I still don’t understand her most recent explanation, so I could just be ignorant) that the authors are confused by the fact that condensation occurs only when pressure drops. They take this to mean that condensation causes a pressure drop, when in fact condensation reduces the pressure drop.
Steve:
A water molecule condenses when random encounters with other vapor molecules leave it almost stationary and not vibrating, and it just happens to be next to another such stationary and not vibrating water molecule. It evaporates when its liquid neighbors just so happen, by chance, to kick it super-hard and it has the energy to escape the liquid. At a certain temperature, the chance of either happening is equal and the gas is saturated with liquid. At a lower temperature, the chance of condensation is greater than that of evaporation, so the liquid condenses. You will note that in order for the water molecule to come to a stand-still, another molecule, say a nitrogen molecule in the air, must receive all its vibrational and translational kinetic energy through the chance encounter.
In Thermodynamics, we say that the “latent heat” is passing into the gas. Meanwhile, the water has not cooled down. It has lost most of its heat, but its temperature remains constant. Thus we see that the relationship between “heat” and “temperature” is subtle. I claim that my use of the words “loss” and “gain” are unambiguous in the context of the Thermodynamic definitions of “heat” and “work” and “temperature”. Outside these definitions, where a rise in “temperature” occurs if an only if there is an addition of something mysterious called “heat”, things get fuzzy.
Also, you will see that condensation is a statistical process, and does not happen immediately. There is nothing wrong with us imagining the pressure of a gas dropping rapidly to below the condensation point as we expand the gas in a cylinder, and the condensation happening later. In that case, we will in fact see the pressure of the gas reach a minimum at the end of the expansion and rise after that during the condensation process. Indeed, this is how a cloud chamber works. The condensation occurs when a charged particle goes through the super-saturated vapor.
Kevan Hashemi says:
January 27, 2011 at 12:43 am
Steve,
I agree with your description beginning “I’m a visual thinker.” . . . .
Laurie says, . . . . .that’s why graphs and diagrams are good. They are worth a thousand words.
http://en.wikipedia.org/wiki/File:Water_cycle.png
Kevan Hashemi says:
January 27, 2011 at 12:43 am
“In Anastassia’s paper, it seems to me (and recall that I still don’t understand her most recent explanation, so I could just be ignorant) that the authors are confused by the fact that condensation occurs only when pressure drops. They take this to mean that condensation causes a pressure drop, when in fact condensation reduces the pressure drop.”
Brian H says:
January 27, 2011 at 12:18 am
“wayne & steve;
you’re both trying to imagine what happens, and failing. 100% of the latent heat is transferred to the surrounding molecules. A window pane that condenses water vapour is warmed by that process. Air temperature cannot drop below the “Dew point” because condensing the dew dumps heat into the air, until humidity is lowered to the point that the dew point also drops. And so on. Real heat is required to evaporate water (which is why sweat succeeds in cooling your skin). And condensing it releases all that heat again.”
Thanks for all comments in trying to explain to me what happens to the energy of latent heat. I must admit that I find the popular literature confusing. The basic statement among every meteorology text I have found can be summarized as “latent heat is transferred to the atmosphere which is why clouds make the local atmosphere so warm.” Can’t get much plainer than that!
I’m still trying to figure out the mechanism by which this heat is physically transferred to the surrounding air – conductive? radiative? What physically happens when those water molecules collide but do not repel each other? It isn’t a chemical bond, so I don’t expect a sudden radiative heat transfer due to electrons falling to a lower orbital. But is that what’s happening? Is it a pseudo-chemical bond in which radiative heat transfer must occur? Because as far as kinetic energy is concerned, all I see are water molecules getting gradually slower as they rise in altitude. I don’t understand why they could suddenly have a burst of kinetic energy, transferred to the surrounding air, when they finally stick together. I also keep finding references to “the potential energy gain due to altitude gain must be balanced by a loss of kinetic energy” (for adiabatic cooling).
If I boil water in my kitchen (near sea level) it will stop increasing in temperature at 100 C because it must go through a state change – heat of vaporization is required. Imagine that I can input precisely the heat needed to achieve vaporization. The steam that comes off is still 100 C, exactly the same temperature as the water. What do I gain by inputting all of that extra energy? Not temperature (average kinetic energy) but vapor pressure. In our atmosphere, the steam can now do something it wasn’t able to before – climb. There is the work done of pushing out, but even more obvious is that as it climbs it must be doing work.
So my 100 C rising steam is using some portion of it’s internal kinetic energy just to climb, not transfer heat. Before vaporization it was transferring energy to the environment as heat, and as steam it will continue to do so. But it seems like the latent heat goes into the climbing, not the heat radiation. We know that, eventually, the heat of vaporization put in must come back out as heat. Won’t that happen as the condensed water falls and ultimately hits the ground?
Basically, it’s a timing issue with me. I don’t understand why the energy of latent heat must be expressed as a heat transfer at the moment of condensation in the atmosphere, as opposed to a heat transfer spread throughout the entire up/down cycle.
Assuming that it must be expressed as a heat transfer at the moment of condensation, does adiabatic condensation follow an exact reverse process of the original vaporization? A LOT of heat has to be input to achieve that vaporization, with no change in temperature to the water. So does a LOT of work need to be done at condensation, with no change in temperature to the water vapor? At the dew point the air mass will rise and expand with no reduction in temperature, eventually BANG – condensation, and afterwards temperature can continue to drop? Or does the latent heat basically keep the air mass stuck at the same altitude until, via heat transfer to surrounding air, condensation occurs?
It’s been a busy week so I’ve not had time to follow this discussion in detail or to respond to Anastassia’s comments.
I left the discussion after she mentioned the simple model of a flat, isothermal Earth (to which I narrowly avoided quipping that that’s how many climate modellers see it). But I was reminded of the (classic) conditions for natural (free) convection in a compressible fluid (without phase change); and the heat transfer within. To date, this thread hasn’t mentioned Grashof, Prandtl or Nusselt.
Free convection is due to body forces; those due to gravity.
Forced convection is due to surface forces; those due to fluid pressure, exerted “mechanically” from “outside”.
The Grashof number is the ratio of buoyancy to viscous force.
The Prandtl number is the ratio of momentum to thermal diffusivity.
The Nusselt number is the ratio of convective to conductive heat transfer.
There is no free convection until the Rayleigh number (Gr.Pr) exceeds a threshold. All heat transfer is conductive below that threshold. (Radiative heating is insignificant near the surface when compared to conductive and subsequent convective.)
For free convection to occur, it is only necessary for the buouyant forces to overcome the viscous and gravitational ones; by thermal (conductive) expansion of the fluid.
It is not necessary for (part of) the fluid to undergo any phase change for free convection to occur. If it does; does warm air rise above a fog in calm conditions?
As a final short note: The Earth’s surface is far from an isothermal plane. It has vast thermal gradients that change with time.
Steve, you say, “I’m still trying to figure out the mechanism by which this heat is physically transferred to the surrounding air – conductive? radiative?”
I tried to answer that question in my second comment tonight. Did you see my description of how a water molecule becomes bound to others, as a result of statistical chance, and how it might escape. If you stick to your buzzing molecule picture, it will all work out.
Note that “potential energy” does not exist as a thing. It cannot be detected. We define it to help us do calculations more quickly.
Water molecules bind to one another when they make liquid, and it’s hard to get them apart. It’s the same as the sun and a planet: hard to pull them apart. But if you let go of the planet, it won’t hit the sun, it will zip past like a comet. To make a planet collide with the sun, you have to stop it moving very near the sun. All this will make sense if you don’t get distracted by the concept of “potential energy” and “heat” as they are commonly misunderstood in science fiction and school text books.
Brian H says:
January 27, 2011 at 12:18 am
wayne & steve;
you’re both trying to imagine what happens, and failing. 100% of the latent heat is transferred to the surrounding molecules. A window pane that condenses water vapour is warmed by that process. Air temperature cannot drop below the “Dew point” because condensing the dew dumps heat into the air, until humidity is lowered to the point that the dew point also drops. And so on.
———
Brian, you might re-read my comment giving Steve a few questions to think about. Latent heat until condensing begins is potential, or are you saying you disagree?
Kevan Hashemi says:
January 27, 2011 at 5:01 pm
…
Note that “potential energy” does not exist as a thing.
——
That potential energy does exist just as gravitaional potential energy exists but you are correct that it is invisible in normal settings until you devise the correct experiment to make it manifest itself, then you do see it is in fact real.
Kevan, I restated that for Steve might take your words so literal that once again it is out of reality though I understood your meaning.
Kevan Hashemi says:
January 27, 2011 at 5:01 pm
“Steve, you say, “I’m still trying to figure out the mechanism by which this heat is physically transferred to the surrounding air – conductive? radiative?”…… I tried to answer that question in my second comment tonight. Did you see my description of how a water molecule becomes bound to others, as a result of statistical chance, and how it might escape. If you stick to your buzzing molecule picture, it will all work out.”
I did see your explanation, but as soon as I read “A water molecule condenses when random encounters with other vapor molecules leave it almost stationary and not vibrating” I lost understanding. Water is still condensed as 99 C on my stove. That is a lot of kinetic energy – those condensed water molecules are most certainly moving and vibrating! Why must this be different for a gas? “Almost stationary and not vibrating” sounds like “almost absolute zero” to me, and the water vapor in a cloud is well above that temperature.
I did more of my own research and it looks like my question, “Is it a pseudo-chemical bond in which radiative heat transfer must occur?” points to the correct answer.
I know about hydrogen bonds but I didn’t realize they resulted in more stable electron configurations. They are pseudo-covalent bonds. Read this from 1999:
http://www.sciencedaily.com/releases/1999/01/990121074852.htm
At vaporization, energy breaks these hydrogen bonds, leaving the individual water molecules with all electrons in their “standard” covalent bonds. At condensation hydrogen bonds reform at an average of 2 – 3.6 hydrogen bonds per water molecule, depending on conditions (and experimentally there is some debate). As with any electron moving into a more stable covalent bond, some energy must be radiated immediately as a photon.
I think that kinda answers it for me. At condensation there will an immediate radiation of heat commensurate to the energy of the hydrogen bonds formed. So condensed air must indeed transfer latent heat into the atmosphere at the moment of condensation. Not during it’s ascent. Not when the water hits the ground. But the instant those electrons go to a lower energy state.
steve;
There’s a wee problem with your “rising steam at 100°C” image. TANSTAAFL. (No free lunches). At exactly 100°C, it can’t “use” its heat to expand (become less dense) and rise without cooling — which it can only do by condensing (some of it, enough to balance the energy budget). So rising steam always spawns lotsa visible mist droplets. (Unless it was live dry superheated steam, which has some energy to play with until it drops to 100°C., at which point the mist starts to form.)
Steve:
Yes, the reason liquid water molecules are hard to separate is because of hydrogen bonds. But you end with, “At condensation there will an immediate radiation of heat commensurate to the energy of the hydrogen bonds formed.” Absolutely not. Who said anything about radiation? You made that up yourself. Nothing is radiated. The reason the gas gets hot is because of the statistical reason I gave you: only when a water molecule is deprived of most of its kinetic energy by random collisions can it be bound to another water molecule. You can figure all all this out in terms of molecules bouncing around. It’s as simple as that. That’s Statistical Mechanics, and it works fine. There is no radiation involved. Why do you want to make it more complicated?
As to “water at 99C” being hot, well, that’s true. But what do you mean by “hot”? Two bodies are at the same temperature when they exchange no heat. That does not mean that they contain the same amount of heat per kilogram or per atom. Water contains far more heat per kilogram than iron at the same temperature. Steam contains far more heat per kilogram than water at the same temperature. What’s the problem with that?
wayne
I generally agree. But the diurnal changes of surface pressure are complex in nature and have also to do with temperature. In our paper we considered the stationary state with a continuous force laterally as long as the water is falling out. If we consider a hypothetical case when clouds are hanging in the air for a long time but no rainfall occurs, this means that condensation is compensated by evaporation on a small scale equal to the cloud size. In this case, obviously, there will be no average pressure reduction in the area covered by the clouds. The pressure gradient will be located within each particular cloud.
Kevan
Let me propose some additional food for thought. Let us take two adjacent boxes of equal size, 1 and 2, each containing 1 mol of gas. Box 2 is warmer than box 1 by T2-T1 and, hence, has a pressure access. If we let the partition between the boxes move under the action of the higher pressure, we will see an oscillating motion. It will continue until the temperatures and pressures equate. The partition returns to its central position.
However, the same thermodynamic equilibrium can set in differently: if we just allow for heat transfer between the boxes. If heat transfer is efficient, no motion will develop. The partition will not move at all.
Now consider the case when the pressure difference between the boxes is due to the difference in the amount of gas. That is, box 2 contains 2 mol of gas and box 1 contains 1 mol of gas. Temperatures are the same. In this case there is no way to reach the equilibrium other than to move the partition. Gas in box 2 will expand performing work on gas in box 1. When the resulting kinetic energy dissipates and the equilibrium sets in, the partition will no longer be in the center. It will be displaced towards box 1, such that molar densities on both sides of it coincide.
To summarize, in the first case work may or may not be performed while the equilibrium is being reached. In the second case, there is no way to reach the equilibrium other than by doing work (of the gas in box 2 on the gas in box 1).
In this sense it is misleading to quantitatively compare the “relative pressure rise” due to latent heat release (“warming”) with the pressure difference caused by the mass removal of the gas. Heat and work are not the same.
Anastassia:
Thank you for your further explanation, which I found thought-provoking.
You say, “If we let the partition between the boxes move under the action of the higher pressure, we will see an oscillating motion.” I suppose you mean the gas on each side will act as a spring, with the partition as the weight, so we get simple harmonic motion. If we allow the partition to conduct heat, I see that its average position will move to the center. Otherwise, the partition can remain away from the center forever.
You go on to say, “If the heat transfer is efficient, no motion will develop.” For this to be true, the mass of the partition has to be so large that the pressure difference causes only negligible acceleration during the time it takes for the temperature to equalize. I can’t think of any physical material that would meet that requirement. So you must be talking about fixing the partition in place with glue or a few nails.
Now you talk about a pressure difference and how, “In this case there is no way to reach the equilibrium other than to move the partition. ” Well, that’s true. If your partition is impermeable to pressure, the partition must move. But it’s also true that if your partition is impermeable to heat (insulating), the partition will have to move.
You say, “In the second case, there is no way to reach the equilibrium other than by doing work ” I disagree. You could make the partition vanish in an instant, and the two bodies of gas would mix freely without doing any work. We could make the partition out of thin latex and pop it. The mixing would be isenthalpic, but not isentropic. Or we could also put a throttle between the two, and let the gas go through the throttle without pushing anything around.
I agree that heat and work are different, but I don’t think your examples have pointed out the difference. Furthermore, the fact remains that moist air expands more than dry air when the two experience the same pressure drop. Moist air will end up less dense. It will float above any surrounding dry air.
Anastassia Makarieva says:
January 28, 2011 at 10:43 am
…
I generally agree. But the diurnal changes of surface pressure are complex in nature and have also to do with temperature.
—
You are right, I’m pulling this discussion into some rather small effects that overall might get lost. I had already come to the realization that there is also warming and cooling in the diurnal cycle and with that comes expansion and contraction in addition to the moisture aspect.
Have you tried Dr. Tom Vonk? I don’t know him personally but on the pure physics side and from what I have read in his posts and comments he seems to have a good background of proper physics. On the observation and logical side I see your paper has a big place in atmosphere physics, for sure. Jeff Id had it right, this aspect is important, very important. Can’t believe they left this out of the models, no wonder they are having problems mimicking reality.
I like your site. I’ve commented at wuwt before what I call myself, a conservationalist, so your site reverberates my concerns, especially about the forests. So many people look at all plant life here as generally the same without considering the depth of the roots, trees rule here, and that gets right back to your view on a moisture drivers in atmosphere.
It took me more than a month to decipher Dr. Ferenc Miskolczi’s paper, on line at a time, taking a copy of his simple budget chart at the top of his paper and using a paint program drawing arrows on it, all of the ties that the equations were saying. Finally I understood. It might take longer to absorb your paper. Tracing some of the equations with the help of the AMS dictionary this is much deeper than even his, but, this is what I like to do so I’ll give it a try.
I won’t comment back unless I have something to add so you might check back here from time to time, OR, post another article here at WUWT, clarifying some of the complex relationships. As myself, many here are not atmospheric scientists per se but can understand it all given the time to absorb the concepts and relationships. If you post an article on another site, drop a note here.
One more thing, it is the wind’s velocity, in general, that greatly dictates the evaporation rates removing the saturated air from the surface, temperature has it’s place but to a lesser degree. I don’t remember reading that recursive, self seeding, aspect coming into play in the equations but maybe I just skimmed over it. If you know the equation numbers where that interplay resides, just comment back the equation numbers. Later.
Kevan
For me it is a pleasure to discuss all this, so thank you for your further comments. We are looking for interest, that is why this unusual appeal.
In both cases in the box example we originally nail the partition such that it is, in your words, impermeable for pressure.
The important distinction is that if the partition is permeable for heat, in the first box the equilibrium sets in without generating any motion. In the second case, the disequilibrium will infinitely persists until the partition is allowed to move. If we remove the partition, as you point out, we will also see air motion in the second box.
The use of throttle will equally affect the motion in both boxes. This is just equivalent to introducing resistance for the flow.
This box example illustrates the well-known point that if you want to obtain work from heat, you must be concerned about the efficiency. That is, about the share of extra pressure that will leak as heat without performing any work.
You say
Several dozen comments ago I wrote:
In essence, we do not seem to be in disagreement. However, your general conclusion, about moist air floating above any surrounding dry air, neglects all those ifs and is equivalent to neglecting the efficiency of transformation of heat to work.
Let me also say that while discussing buoyancy is undoubtedly interesting per se, our paper is not about buoyancy and not about the impact of condensation on buoyancy. The condensational pressure gradient force can make the air rise even if it is negatively buoyant in comparison to the surrounding air. By the way, atmospheric updrafts characterised by negative buoyancy are pretty common (see, e.g., Folkins 2006).
wayne
Thank you for your comments. Surface evaporation is implicitly taken into account in the condition dNv/dx = 0. This means that despite air pressure falls along the x axis, the saturated concentration of water vapor is maintained constant over the considered isothermal surface by local evaporation. This is discussed in Section 4.5 “Evaporation and condensation”. We have neglected evaporation from droplets.
Regarding forests and their role, you might be interested in reading this paper. In particular, pay attention to Fig. 2c, which compares precipitation patterns in North America (forested) versus China (deforested) at one and the same latitude.
I am signed to receive comments from this thread, so please, if further questions arise, I will be delighted to discuss them as time permits. When we have new work published, I will certainly put a note here.
There are several well-described and empirically observable physical phenomena that can be called “cousins” of the condensational atmospheric dynamics. Contemplating these phenomena may help the reader appreciate what we are talking about. I talked above about one such phenomenon — the heat pipes. Let me here to mention another one — the osmosis. Indeed, condensation-induced atmospheric dynamics can be considered as a very peculiar case of osmosis.
In agreement with Dalton’s law, partial pressures of particular components of gas mixtures or liquid solutions tend to spatial homogeneity independently of each other. Consider two mixtures with different concentrations of various components that are separated by a semipermeable membrane, which impedes spatial propagation of one of the components and prevents it from reaching the equilibrium distribution. The resulting equilibrium distribution of partial pressures of all other components will be associated with a pressure gradient across the membrane. The trans-membrane pressure difference will be equal to the magnitude of deviation of the partial pressure of the considered non-equilibrium component from equilibrum. If now the membrane is removed, the dynamic fluxes of liquid or gas will follow governed by this pressure gradient until the mixture pressures and concentrations of all constituents in the two areas equate.
In the atmosphere, the role of semipermeable membrane of a unique nature is played by the vertical temperature gradient – it selectively removes, via condensation, one of the gases from the mixture (water vapor) and does not allow it to propagate to the upper colder atmosphere in quantities sufficient for the restoration of component equilibrium of water vapor in the gravitational field. At the same time, lacking material essence, this unusual “membrane”, unlike the conventional osmotic membrane, is penetrable to the dynamic flow of mixture as a whole, sustaining continuous air circulation. In the ordinary osmosis, the dynamic flow (that destroys the pressure difference) should be intermitted by periods of molecular diffusion via the semipermeable membrane, when the osmoitc pressure difference is regained. In the case of the condensational pressure gradient force, the dynamic flow itself sustains the “osmotic” pressure difference by bringing water vapor to the area of condensation.
It’s amazing Anastassia how different branches of science always tend to cross at some point. You bring in osmosis and my major was physiology and my final paper before graduation long ago was the osmotic transport of c14 tagged glucose across the semi permeable membrane in the intestines of a species of worms (pig gut worms actually, can’t recall the species). So, that last explanation is plain ‘English’ to me!
You must be speaking of what would visually show itself at the rolling tops of clouds, not the bottoms where condensation first appears, in the cumulus case the undefined silky gray bottoms. Of course I had never considered osmosis would have a hand in the replenishment of the water vapor. That is interesting.
Or, I guess some of that effect would occur at any stark edge of a cloud where clear air meets the saturated vapor, that in cumulus case, is the constant rolling at the distinct edges and tops and stratus type at mainly the tops. Is that close or way off?
You could be speaking more at the smaller molecular level and this occurring anytime condensation occurs which leaves that depleted parcel exposed with a osmotic gradient but there I don’t visualize an edge.
wayne
I am happy to have found a reader interested in this aspect. Personally I find it fascinating.
I presume that by ‘edge’ you mean the region occupied by the membrane, which separates solutions with different concentrations. In the conventional osmosis the concentrations change stepwise across the edge (membrane). If we take the thickness of the edge equal to zero, the non-equilibrium concentration gradient at this point is infinite.
In the atmosphere there is no edge. It would exist if the air temperature dropped stepwise at some height. It does not. It drops smoothly as the air ascends. The non-equilibrium gradient of vapor pressure is finite. In this sense all the atmospheric column where the moist saturated air ascends acts as a ‘membrane’. This ‘membrane’ removes a certain share of water vapor from each saturated air volume as the latter ascends by a certain height.
Here’s a complexification (note to Anna — that’s a made-up word! Don’t borrow it. 😉 ):
My understanding is that the bulk of precipitation begins its condensation/joining cycle not as “droplets” but as ice crystals (since the air temperature high in rain clouds tends to be well below 0°C), and then melt into raindrops on the way down. Hail, of course, goes through numerous fall-rise cycles into the cold zone to build up.
All of which introduces another layer or two of latent heat exchanges to be factored in.
Oops. I just checked, and it does indeed exist! I guess I should have used “complification”! 😉
Anastassia, I didn’t understand at first what you were trying to portray but it’s becoming clear. I had a problem grasping what exactly “atmospheric column where the moist saturated air ascends” statement meant in relation to the osmosis. Outside of that column you must mean air that has less humidity, as in a downdraft around that column. In that context I clearly see the virtual ‘membrane’ and the water vapor in the column would always be moving outward to mix with the less humid surroundings therefore losing a bit of humidity as it rose.
Re-reading your first comment over again, twice, I see you are trying to tell me the same thing I was trying to visualize. You were also describing the ‘rolling’ or ‘sustaining continuous air circulation’ as you put it and I went right by it. I’m not quite used to some of the proper atmospheric physics nomenclature, but I’m starting to get it down. I read the whole section four with no problem but section one, well, in general I understand but I would like to grasp each equation and that’s a bit slower. Thanks so much for opening my eyes to some new aspects. Spent a whole summer last year watching clouds float by but now I’ll never look at them quite the same. I need to read section 2 & 3.
“Kevan Hashemi says:
January 28, 2011 at 5:43 am
“Steve:
Yes, the reason liquid water molecules are hard to separate is because of hydrogen bonds. But you end with, “At condensation there will an immediate radiation of heat commensurate to the energy of the hydrogen bonds formed.” Absolutely not. Who said anything about radiation? You made that up yourself. Nothing is radiated. The reason the gas gets hot is because of the statistical reason I gave you: only when a water molecule is . You can figure all all this out in terms of molecules bouncing around. It’s as simple as that. That’s Statistical Mechanics, and it works fine. There is no radiation involved. Why do you want to make it more complicated?”
How does stating that the energy loss must be in the form of radiation make it more complicated?
By definition, during a phase transition there is no increase/decrease in average kinetic energy (temperature) of the molecules. Going in the heating direction, that means that at vaporization energy is transferred into a mass of liquid water with none of that energy showing up as an increase in kinetic energy. Water molecules are not gaining linear momentum for their collisions. For energy to go into this mass without a temperature change, SOMETHING must be gaining momentum. That ends up being the momentum of the electrons (angular momentum). Molecular bonds are broken, and the electrons end up in a higher (but less stable) energy state. Do you at least agree with this concept for the heating direction?
An equivalent process must occur in the cooling direction. At condensation, energy is transferred out of the mass of water vapor with no reduction in kinetic energy of water molecules. That energy had to come from somewhere! If not at the gross molecular level (temperature) it’s going to be lost on the atomic level. Somewhere an electron had to weasel it’s way back down into a lower energy state and radiate a photon.
Contrary to making the concept more complicated, I think it makes it easier to envision. If latent heat were a basic heat transfer through molecular collisions then rising water vapor would heat all adjacent gases equally. But as a radiant heat transfer the latent heat is statistically more likely to be absorbed by molecules with the same absorption/emission spectra – other water molecules. Latent heat released upon condensation in the upper atmosphere is more likely to be directly radiated to space. Latent heat released when water vapor condenses at the center of a thundercloud is more likely to heat water molecules (which can then transfer heat to the surrounding air mass by collision). Knowing that the energy transfer is expressed physically as radiation tells me a lot! Of course, someone needs to determine the emission frequencies of energy released by hydrogen bonds at condensation and check for overlaps with the absorption spectra of other atmospheric gases.
David
January 26, 2011 at 11:15 am
I contacted Professor Pielke Sr. several times starting from October 2008 asking for comments/criticisms regarding our work, both on the role of vegetation in driving the hydrological cycle, on the physical bases of condensation induced dynamics and on social issues associated with difficulties of challenging a consensus in climate science and the associated caveats of the peer-review process.
Regarding science, I received two comments from Prof. Pielke, which are as follows. First, Prof. Pielke does not “see how the effect of the changes partial pressure of water vapor can have a major effect relative to the much larger effect of the release of latent heat and other diabatic effects as they alter the vertical and horizontal pressure gradient”. Second, “if the atmosphere is in (or close to) hydrostatic balance, the mass remains unchanged overhead regardless of the phase the water is in”, such that condensation within the atmospheric column cannot instantaneously reduce local air pressure at the surface.
Prof. Pielke advised that we should submit our considerations to an AGU or AMS journal where they will be peer-reviewed. He also advised that we should consider submitting to physical journals as “the advantage of having physicists review your work is that they are not as likely to have some of the biases you report.” In response to our query whether he would find it possible to make a public comment on our work, Prof. Pielke clarified that he “receive(s) quite a few communications to comment on research, and prefer(s) not to generally do that”.
Posted with permission of Prof. Pielke Sr.
Prof. Pielke…“if the atmosphere is in (or close to) hydrostatic balance, the mass remains unchanged overhead regardless of the phase the water is in”, such that condensation within the atmospheric column cannot instantaneously reduce local air pressure at the surface.
Is he saying that the mass must remain unchanged because that is part of the definition of hydrostatic equilibrium? Or does it “just not happen that way” (which may be true)?
Looking at the force balance diagram for hydrostatic equilibrium(http://en.wikipedia.org/wiki/File:Hydrostatic_equilibrium.svg), I don’t see “mass remains constant” as a requirement. If the mass of the volume increases in that diagram then I can see two ways to maintain hydrostatic equilibrium. Either increase the upward force of gas from below, or reduce the downward force of gas from above.
Water condensation will lead to a loss of vapor pressure coupled with a large radiation of heat. That heat can accomplish two things – increase the vapor pressure of gases pushing up from below, and decrease the vapor pressure of gases pushing down from above.