Water in the atmosphere

[QUITTNER]

[[Mod. note -- I apologise for the delay in posting this article,
which the author submitted on Thursday 18 June 2015. -- jt]]

We all know that water is a fluid unless the temperature is below
freezing (ice) or above boiling (steam). Yet according to the psycho-
metric chart there is water as a gas in the atmosphere at tempera-
tures at which water is supposed to be in liquid form. How come?

[[Mod. note --
What's going on here is a (dynamic) equilibrium between the liquid and
gas phases, or more precdisely. The first paragraph of
http://en.wikipedia.org/wiki/Vapor-liquid_equilibrium
gives a brief introduction.
-- jt]]

[Roland Franzius]

Am 22.06.2015 um 05:11 schrieb QUITTNER:
> [[Mod. note -- I apologise for the delay in posting this article,
> which the author submitted on Thursday 18 June 2015. -- jt]]
>
> We all know that water is a fluid unless the temperature is below
> freezing (ice) or above boiling (steam). Yet according to the psycho-
> metric chart there is water as a gas in the atmosphere at tempera-
> tures at which water is supposed to be in liquid form. How come?

Water-gas transition (boiling point) is an surface effect and as such it
is strongly dependent on the external pressure for bubble creation.

Gas-water transition is not only pressure dependent but at low partial
pressure needs some external help to produce macroscopic liqid drops.

Because of the giant specific surface energy of nano-small droplets
energy gain by condensing is negative.

So condensation in the pressure depenendend temperature range between
freezing and boiling point may occur only at the presence of hygroscopic
dust particles.

Most of the cloud creation occurs via gas-ice freezing because the
surface energy of snow crystals is negative: in contrast to the surface
minimizing water drops they tend to maximize their surface.

This is physical principle driving the water engineof the atmosphere:
Water is converted to gas by the sun light energy at the ground, mostly
on the green ground.

The hot water gas is raising because the hot air with a percentage of
the extremly lightwighted water hot molecules (H2O 18 compared to N2 28,
O2 32) act like a hat air ballon with respect to the comparativley low
temperature atmosphere .

This goes on until, by work against gravity aka adiabatic volume
expansion and radiation, at 4000-6000 m the water is sublimating to snow
flakes.

The gas-snow transition heats the O2/N2 gas host atmosphere to the
extreme like an explosion so that the atmospheric ballon may take a
second shot to raise until at about 10000 m all internal energy is
converted to gravitational energy.

Additionally, because the ballon is now above the CO2/H2O infrared
radiation barrier, it radiates its remaining energy into space until its
cooled down to -80C, as you see it recorded on your flight monitor at
30000 ft.

Because of the extreme molecular surface energies on water with its
strong dipol moments, electrons are unevenly distributed between the
snow and gas in the flake formation.

Gas, snow and finally, more downwards, the melted raindrops are moving
at different directions and velocities, that's the source of rapidly
growing large area charge density fluctuations.

The local electric fields are limited by discharging the charged layers
and the earth surface below, that got electric charged by rain, via
lightnings and the earth.

--

Roland Franzius

[David Staup]

your question should be approached differently if you want to understand.

first learn about evaporation and sublimation, the two mechanisms that
provide water molecules to the atmosphere. those two are relatively easy
to understand. Hint: Temperatures are a measure of the mean energies of
all the molecules being measured. A bell curve of energies, some lower
and some higher than that which represents the "temperature" of the
material.

then learn about why and how water leaves the atmosphere under real
world conditions.

only then will "equilibrium" be understandable.

[Gregor Scholten]

QUITTNER wrote:

> We all know that water is a fluid unless the temperature is below
> freezing (ice) or above boiling (steam). Yet according to the psycho-
> metric chart there is water as a gas in the atmosphere at tempera-
> tures at which water is supposed to be in liquid form. How come?

There are different approaches to consider this. One approach is a
microscopic one: imagine the water molecules in the liquid phase as
being equipped with different kinetic energies. At temperatues below the
boiling point, the kinetic energy of the most molecules is too low to
leave the liquid phase into the gas phase, however, some few molecules
have enough kinetic energy to do so. Those few molecule therefore leave
the liquid phase and make up a portion of steam in the atmosphere.

Another approach is a rather thermodynamic one. Imagine a cylinder with
a piston that establishes a constant pressure inside, filled with a
phase of liquid water and a phase of steam. If the established pressure
is higher than the vapor pressure of water for the current temperature
(e.g. 0.023 bar for 20 °C), more water molecules transition from the
steam phase to the liqid than the other way round, so the steam phase
will disappear. If, vice versa, the established pressure is higher than
the vapor pressure, more molecules transition from the liquid phase to
the steam phase, the liquid phase dissapears. If the established
pressure exactly equals the vapor pressure, both phases are in
equilibrium, and therefore co-exist. This is the case e.g. for a
pressure of 1 bar at a temperature of 100 °C.

Now replace the cylinder and the piston by an open vessel filled with
liquid water in contact to an atmosphere with e.g. 1 bar pressure that
does not only contain steam, but also other gases. Now, the number of
water molecules that transition from the liquid phase to the steam phase
and the other way round is no longer determined by the total atmospheric
pressure, but rather by the partial pressure of the steam
portion. Imagine the total atmospheric pressure as being decomposed into
contributions from all the different gases in the atmosphere. The higher
the portion of a single in the atmoshere is, the higher is the partial
pressure of this gas. So now, the portion of steam in the atmosphere
takes that value for which the partial pressure of steam equals the
vapor pressure for the current temperature.

Or let's better say: it tends to take that value. In reality, the actual
value is always a little lower, what is indicated by a humidity of less
than 100 percent.

At 20 °C, the vapor pressure of water is 0.023 bar, so the portion of
steam in the atmopshere tends to take the value for which the partial
pressure of steam is 0.023 bar. At 100 °C, the vapor pressure becomes 1
bar, so the portion of steam takes the value for which the partial
pressure of steam is 1 bar, which means a portion of ~ 100 percent at 1
bar total pressure - the water in the vessel boils and evaporates
completely.

[James McGinn]

[Moderator's note: Please send unencoded plain text with unquoted lines
shorter than 72 characters to avoid the lines split by "=". -P.H.]

On Sunday, June 21, 2015 at 8:11:36 PM UTC-7, QUITTNER wrote:

" . . . according to the psychometric chart there is water as a gas in the =
atmosphere at temperatures at which water is supposed to be in liquid form.=
How come?"

The psychometric chart is factually wrong (mistaken) but in terms of practi=
cal usage it is correct, or correct enough to be useful. Moisture in the at=
mosphere does not actually exist as "steam." IOW, there is no monomolecula=
r H2O in earth's atmosphere. It's far too cool for that. However, surface=
tension of evaporate droplets increases exponentially with respect to the =
ratio of surface area to mass. (1) The net effect of this is to allow the =
formation of incredibly small droplets (smaller than 25, larger than 3 mole=
cules per droplet) that maintain coherence (despite their small mass/size).=
These are, for psychometric purposes, effectively "steam." And as long a=
s the radius of the droplet is smaller than a photon they are invisible. Bu=
t, to be perfectly accurate, it isn't actually steam (monomolecular H2O). A=
nd the general belief that there is such thing as "cold steam" in earth's =
atmosphere is just an urban legend.

1. The tendency of the surface tension of H2O to increase exponentially wit=
h surface area is one of the many anomalous propertis of H2O, the basis of =
which is not well known/accepted.

James McGinn

[Moderator's note: At least some people use "steam" to refer to water
which is a) hot and b) in the form of droplets large enough to appear
white, such as comes out of a boiling kettle, and use the term "water
vapour" to refer to water in true gaseous form, whatever the
temperature. This is what the poster calls "steam". -P.H.]

[Poutnik]

Dne 13/01/2016 v 21:52 James McGinn napsal(a):

>
> The psychometric chart is factually wrong (mistaken) ........
...
> These are, for psychometric purposes, ......

I am not sure if psychology uses term psychometric,
but the proper term in context of water vapours in air
is psychrometric.

--
Poutnik ( the Czech word for a wanderer )

[James McGinn]

On Wednesday, January 13, 2016 at 12:52:40 PM UTC-8, James McGinn wrote:

> [Moderator's note: Please send unencoded plain text with unquoted lines
> shorter than 72 characters to avoid the lines split by "=". -P.H.]

Aha! Okay. I think I know what you mean by this.

[Moderator's note: Much better!!! -P.H.]

> [Moderator's note: At least some people use "steam" . . .

One way to avoid confusion is to refer to gaseous H2O (what I call
steam) as H2O(g) and lower temperature evaporate H2O that we find
in the atmosphere (what I call vapor) as H2O(l). And, of course,
ice as H2O(s). Where g = gas, l = liquid, and s = solid.
Accordingly, there is no H2O(g) in earth's atmosphere. This is
a myth. It is all H2O(l) or H2O(s).

[Moderator's note: That is clearer. -P.H.]

[John Heath]

On Wednesday, January 13, 2016 at 3:52:40 PM UTC-5, James McGinn wrote:
[[Mod. note -- 28 excessively-quoted lines snipped here. -- jt]]

>
> [Moderator's note: At least some people use "steam" to refer to water
> which is a) hot and b) in the form of droplets large enough to appear
> white, such as comes out of a boiling kettle, and use the term "water
> vapour" to refer to water in true gaseous form, whatever the
> temperature. This is what the poster calls "steam". -P.H.]

And as long as the radius of the droplet

is smaller than a photon they are invisible.

That is a nice way to put it. Very small insects can survive a
microwave oven as they are smaller than the microwave wave length.
This would be another example of smaller than the wave length
therefore invisible to the photon.

[Thomas Koenig]

James McGinn <jimmc...@gmail.com> schrieb:

> The psychometric chart is factually wrong (mistaken) but in terms of practi=
> cal usage it is correct, or correct enough to be useful. Moisture in the at=
> mosphere does not actually exist as "steam." IOW, there is no monomolecula=
> r H2O in earth's atmosphere. It's far too cool for that.

The vapor pressure of water is non-zero below the boiling point of
water. Water in air exists as a mixture of (almost) perfect cases.
In equilibrium to liquid water, the partial pressure of the water
in air equals the vapor pressure of water.

If what you said here

> However, surface=
> tension of evaporate droplets increases exponentially with respect to the =
> ratio of surface area to mass. (1) The net effect of this is to allow the =
> formation of incredibly small droplets (smaller than 25, larger than 3 mole=
> cules per droplet) that maintain coherence

were true, there would be rather large observable consequences. For
exapmple, air containing water would be heavier than dry air (ideal gas
law), and our weather would be dramatically different. Also, every
calculation of every cooling tower would be quite wrong.

I find that hard to credit.

[Poutnik]

Dne 17/01/2016 v 09:36 Thomas Koenig napsal(a):

Good response.

Also wet air thermal condutivity would be lower,
while observed higher,
sound speed would be lower, while observed higher,
water vapour diffusion coefficient would be much lower than observed
water content wuould be up 3-200times higher than observed.
water vibration-rotation IR and rotation far IR spectra would be different
water vapour reactivity would be different.
water evaporation latent heat would
have very different dependence on temperature
etc etc

For ambient conditions
is monomer : dimer ratio about 1 : 1000,
while for steam above boling water about 1 : 20

--
Poutnik ( the Czech word for a wanderer )

Knowledge makes great men humble, but small men arrogant.

[J. J. Lodder]

John Heath <heath...@gmail.com> wrote:

> On Wednesday, January 13, 2016 at 3:52:40 PM UTC-5, James McGinn wrote:
> [[Mod. note -- 28 excessively-quoted lines snipped here. -- jt]]
> >
> > [Moderator's note: At least some people use "steam" to refer to water
> > which is a) hot and b) in the form of droplets large enough to appear
> > white, such as comes out of a boiling kettle, and use the term "water
> > vapour" to refer to water in true gaseous form, whatever the
> > temperature. This is what the poster calls "steam". -P.H.]
>
> And as long as the radius of the droplet
> is smaller than a photon they are invisible.

A mistake. While it is not possible to resolve the droplet
using optical microscopy the droplet still scatteres light,
which is of course visible.
This is called Tyndall scattering,
and is used to see small particles in suspension.
It is also the effect that allows you to see smoke.

Visibility should not be confused with resolvability.
(think of a star, which is visible, but not resolvable into a disk)

> That is a nice way to put it. Very small insects can survive a
> microwave oven as they are smaller than the microwave wave length.
> This would be another example of smaller than the wave length
> therefore invisible to the photon.

Also a mistake.
Heating in a microwave is cased by the alternating electric field.
(molecules with a permanent electric dipole moment are forced to rotate)

It is not caused by absorbing 'photons',
in the sense that it is a purely classical effect.
RF heating also works at much lower frequencies. (27 MHz for example)
This is used industrially, but for home use
such an installation is unpractically large.

Best,

Jan

[Poutnik]

Dne 17/01/2016 v 10:39 Poutnik napsal(a):

> For ambient conditions
> is monomer : dimer ratio about 1 : 1000,

> while for steam above boiling water about 1 : 20

OOps, my writing mistake,
should be dimer : monomer ratio .

The association constant of water dimer
K = p(dimer)/[p(monomer)]^2 is 0.0501 bar^-1 for 298 K.

Low partial pressure at low temperatures
shifts significantly the equilibrium in favour of the monomer.

[James McGinn]

It's not possible to detect monomers or dimers. So claims are being
made here that can not be refuted or confirmed. And precise numbers are
being asserted, without reference. Which makes it even more suspicious.

[Roland Franzius]

By the fundamental dimensionless constant alpha=1/137 the H-atoms Bohr
radius is 1/137 of the wavelength it emits or absorbs. The same ratio is
in effect for the compton wavelength and the classical elctromagnetic
radius of the electron.

So something seems to be fundamentally wrong in that reasoning. Its a
fundamental fact that teh em-interaction is weak and slow because the
atomic matter is equiped with much too small antennae for an effective
communication.

The ratio of dimensions is a rough measure of times you must try to hit
that invisible object by that a much to long object that resonates
perfectly with a given eigenfrequency. Compare to a peanut to be split
by use of a big axe.

If, On the other hand, both, frequencies and length dimensions, are
roughly equal - as it happens to be in strong interaction models - the
two modes of matter and radiation are not really distinct and with an
interaction constant near 1 no convergent approximation from "no
interaction" seems to be possible.

The correct form of such a statement about microflies in the infrared
oven is that their expected cooking times scale by wavelength/flylength.

And so the story goes that to dtect electromagnetism and its wavelike
form of existence was possible only by the very existence of conducting
metals, that allowed for the construction of antennae of length lambda/4.

--

Roland Franzius

[Poutnik]

Dne 15/01/2016 v 23:18 James McGinn napsal(a):

The association constant for 2 H2O(g) --> (H2O)2 (g)
K =p[(H2O)2]/(p[H2O])^2
is about 0.05 bar^-1 for 298 K.
For saturated vapour tension at 298 cca 0.03 bar
is tension of vapour dimer 0.03^2 . 0.05 = 0.000045 bar.

The H2O(g) at 298 K is only lightly modified wrt ideal gas behaviour
of water monomer by creation of small amount of dimer,
with higher polymers just with traces.

Not even p-V isoterms does not show pressure driven polymeration,
until condensation.

The moderator's shame remains....

[James McGinn]

On Sunday, January 17, 2016 at 12:36:31 AM UTC-8, Thomas

Koenig wrote:

> The vapor pressure of water is non-zero below the boiling point of
> water.

Yes, evaporation. A process that can and does take place even at very
low temperatures (ie. triple point). It is a much lower energy process
than boiling. And, according to what I am asserting here, it would
involve droplets or clusters of H2O, not individual molecules. This
appears to be a contradiction, doesn't it? How can droplets/clusters
that are, indisputably, heavier than individual molecules take less
energy to be separated from the surface than individual molecules? It
appears to contradict the laws of thermodynamics.

Actually it isn't a contradiction. And you, most likely, already know
part of the reason why. As you surely know, H2O is a polar molecule.
Without its polarity the boiling point of H2O would probably be around
-150C. Instead it is 250 degrees higher, 100C. But there is another
part of this story that you don't know. And it's this other part of
this story that explains why the lower temperatures of evaporation is
not a contradiction to the laws of thermodynamics. Unfortunately this
other part of the story isn't something that you can just go look up in
a book. And even though I know this other part of this story (and have
no qualms about explaining it) it is not something I intend to explain
here and now. For the time being let's just refer to this (this
thermodynamic contradiction between evaporation and boiling) as one of
the anomalous properties of water. (One of many.)

> Water in air exists as a mixture of (almost) perfect cases.

I don't know what you mean by "case".

> In equilibrium to liquid water, the partial pressure of the water
> in air equals the vapor pressure of water.

I agree.

> If what you said here

> > . . surface tension of evaporate droplets increases exponentially
> > with respect to the ratio of surface area to mass. (1) The net
> > effect of this is to allow the formation of incredibly small
> > droplets (smaller than 25, larger than 3 molecules per droplet)

> > that maintain coherence
>
> were true, there would be rather large observable consequences. For

> example, air containing water would be heavier than dry air (ideal
> gas law),

Right, if what I am saying is true then, given ideal gas laws (and
Avogadro's law) moist air could only be heavier than dry air
(controlling for all other factors). And that would have HUGE
implications.

> and our weather would be dramatically different.

Our weather wouldn't be any different. But our understanding of what
causes weather would have to change dramatically. The notion that
dominates storm theory, convection, would have to be abandoned and we
would have to start all over since convection is the most fundamental
notion in all of storm theory. (And maybe the most perplexing aspect
thereof involves the question as to how heavier H2O gets so incredibly
high in earth's atmosphere, all the way up to just below the
stratosphere.)

> Also, every calculation of every cooling tower would be quite wrong.

Quite.

> I find that hard to credit.

If not for the fact that I know the, "rest of the story," I too would
find it hard to credit.

[Solving Tornadoes]

On Tuesday, January 19, 2016 at 8:33:32 PM UTC-8, Roland Franzius wrote:

> So something seems to be fundamentally wrong in that reasoning.

I don't know. I don't think anybody does.

Apparently it's all but impossible to know/detect the molecular
quantity of H2O cluster/droplets. It would be good to know at
what size they start to become observable (ie. clouds). My
guess is that is is somewhere around 25 molecules per
cluster/droplet. But it could be 10, 100, or even 1000 for all
I know--for all anybody knows.

[Thomas Koenig]

James McGinn <jimmc...@gmail.com> schrieb:

> Yes, evaporation. A process that can and does take place even at very
> low temperatures (ie. triple point). It is a much lower energy process
> than boiling.

The enthalpy of evaporation of water at boiling point is around
2250 kJ/kg (a figure that most engineers should know by heart).

The enthalpy of evaporation for water ice is around 2830 kJ/kg.

That makes evaporation of water ice a higher energy process than
boiling.

[Poutnik]

Dne 20/01/2016 v 22:11 Solving Tornadoes napsal(a):

Molecular quantity of H2O cluster/droplets
can be determined by many ways.

At molecular level e.g. by rotation far IR spectroscopy
and mass spectroscopy.

At macroscopic level from known dependencies of gas properties on
molecular mass.

e.g. Density = pM/(RT)

soundspeed v = sqrt( gamma . R . T / M )
where gamma is adiabatic constant.

Also from specific thermal capacity and conductivity.

--
Poutnik ( the Czech word for a wanderer )

[James McGinn]

On Thursday, January 21, 2016 at 12:58:00 AM UTC-8, Thomas Koenig wrote:

> The enthalpy of evaporation of water at boiling point is around
> 2250 kJ/kg (a figure that most engineers should know by heart).
>
> The enthalpy of evaporation for water ice is around 2830 kJ/kg.
>
> That makes evaporation of water ice a higher energy process than
> boiling.

I did a search on the internet to find a controlled experiment
that would confirm your assertion here. I couldn't find one.
I did find a wikipedia page, but it involves calculation and
not measurement and it appears they mistakenly included the
assumption that evaporation involve a transition from liquid
to gas, which is certainly not the case, as I've explained.
I will do some more research to see if I can find a
controlled experiment.

[James McGinn]

On Thursday, January 21, 2016 at 1:05:45 AM UTC-8, Poutnik wrote:

> Molecular quantity of H2O cluster/droplets
> can be determined by many ways.

By, "determined," don't you mean inferred and not measured?

> At molecular level e.g. by rotation far IR spectroscopy
> and mass spectroscopy.
>
> At macroscopic level from known dependencies of gas
> properties on molecular mass.

So, they are using IR spectroscopy based on the, to use
your words, "known dependencies of gas properties." But
they have no way of knowing that it actually is a gas.
That is just an assumption. So the results of these
studies are open to interpretation. My interpretation
is that it is not a gas and, therefore, the approach is
fundamentally flawed. But this is one of those things
where everybody can have an opinion and nobody can be
proven wrong.

https://tallbloke.wordpress.com/2014/07/17/unsettled-science-uncertainty-around-the-continuum-absorption-of-water-vapour/
or
https://goo.gl/NAh8m3

"Thus, a deep controversy on the nature of the water vapour
continuum still remains unresolved. The atmospheric science
community has largely sidestepped this controversy, and has
adopted a pragmatic approach. Most radiative transfer codes
used in climate modelling, numerical weather prediction and
remote sensing use a semi-empirical formulation of the
continuum - CKD-model (Clough et al. 1989). This formulation
was tuned to available (mostly laboratory) observations in
rather limited (far-infrared) spectral regions."

[Jonathan Thornburg [remove -animal to reply]]

This thread seems to have run its course. The basic thermodynamics
of water in its various phases is well-understood, and no substantive
arguments to the contrary have emerged. After discussion between the
moderators, we have therefore unanamously agreed to close this thread.

ciao,

--
-- "Jonathan Thornburg [remove -animal to reply]" <jth...@astro.indiana-zebra.edu>
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
"There was of course no way of knowing whether you were being watched
at any given moment. How often, or on what system, the Thought Police
plugged in on any individual wire was guesswork. It was even conceivable
that they watched everybody all the time." -- George Orwell, "1984"