Re: Sometimes people believe things that are nonsense

From	Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups	sci.physics
Subject	Re: Sometimes people believe things that are nonsense
Date	2016-07-19 19:43 +0200
Organization	PointedEars Software (PES)
Message-ID	<2010819.ElGaqSPkdT@PointedEars.de> (permalink)
References	<71e85c18-b8f4-4d46-a93d-d14fb3848e7e@googlegroups.com> <1jsonb9lg3b7cjvib5abkjp49ui85qhopc@4ax.com>

Show all headers | View raw

Michael J.  Strickland wrote:

> On Sun, 3 Jul 2016 10:13:32 -0700 (PDT), James McGinn
> <jimmcginn9@gmail.com> wrote:
> 
> ...
>>The most stupefying myth in all of meteorology is the myth that steam can
>>persist in our atmosphere.
> 
> Steam is water vapor above air saturation density. The steam coming
> out of a kettle is opaque because it is well over saturation density
> (>> 100% humidity) and pushes the air aside as it exits.

Partially true.  It is not the steam that is over 100 % humidity, but the 
*air* is (i.e., there is more water in the air that it can hold; the warmer 
the air, the more water it can hold), *therefore* there is steam.

> Technically, its not persisting in the atmosphere since it has purged the
> atmosphere from its vicinity.

Nonsense.

> As it spreads out, colliding and mixing with the heavier air molecules, it
> loses kinetic energy (cools) due to the work it does against atmospheric
> pressure. By the time it reaches saturation density (100% humidity) it has
> become translucent (almost transparent) instead of opaque. If its density
> increases beyond saturation due to a pressure pulse for instance or
> further cooling, it forms water droplets (clouds).

I am not sure that is a completely correct description either.

> As water vapor (much lighter than air) rises and cools, it condenses
> into water droplets (clouds).

You have omitted the most important part of the story.  For a gas to 
condense to drops that results in clouds, it does not suffice that its 
temperature is reduced; there has to be something *solid* that it can 
*condense on*.  Condensation of water vapor to clouds is possible because 
the air in our atmosphere is not clean: small dust particles (e.g., carried 
away from deserts and ground soil, and from air pollution caused by humans), 
which in this context are called *condensation nuclei*, are intermixed with 
it, and the water vapor condenses *on them* (just like it condenses on a 
pane of window glass; the scientific term of that is *phase boundary*).

<https://en.wikipedia.org/wiki/Rain>

> As water vapor condenses into a cloud, the volume reduction (vapor to
> liquid) reduces the outward positive pressure of the cloud and allows
> more moisture laden air to flow into the cloud. This effect causes the
> cloud to grow in all directions.

How did you get that idea?

> Droplets at the top of the cloud (coldest) fall downward with a very
> small terminal velocity and usually evaporate from air frictional
> heating before falling very far.

Instead, those "droplets" at the top of a cloud are actually condensation 
nuclei surrounded by then-*frozen* *solid* water *ice*.  They fall down 
eventually because there comes a point when their mass becomes to great for 
any upwardly directed airstream (as warm air rises, and the planet’s crust 
is continuously warmed by its main star) to hold in suspense.  Depending on 
the temperature in and below the cloud they *melt* or even evaporate in the 
process.  [AFAIK, it is _not_ any “frictional heating” that determines what 
kind of precipitation, if any, can be expected from falling out of a cloud, 
but temperature and wind conditions in the lower part and below the cloud 
(technically, there is snow/hail from *every* cloud; you can see that in 
winter or in polar areas when and where the temperature of the air below the 
cloud is not high enough to melt the snowflakes/ice pellets).  When the 
temperature below the cloud is just high enough for the falling 
pellets/drops to evaporate before they reach the ground, you can see 
/virga/, “falling streaks”, below the cloud.  The friction between falling 
and rising particles in the cloud, however, allows for a separation of 
electrical charges and the cloud to be statically electrically charged, 
which leads to lightnings as the form of resulting electric discharge inside 
a large cloud, between clouds, or clouds and the ground.]

In weather modification, there is “cloud seeding”: clouds are seeded from 
airplanes with drops of silver iodide as artificial condensation nuclei; 
either to form clouds that can rain of where there would have been little to 
none naturally (i.e., over arid regions and deserts), or to have existing 
clouds rain off before they become to large (you want enough rain, but not 
100 % cloud coverage for your plants; and you want rain, not a hailstorm, 
down on your crops – as cumulus clouds grow *upwards* to develop towards 
cumulonimbuses, they become more likely to be a source of a hailstorm due to 
the much lower temperatures in the upper atmosphere).

<https://en.wikipedia.org/wiki/Cloud_seeding>

> As the cloud grows upward and the temperature at the top drops, colder
> and larger drops form.

Not drops, but pellets of *water ice* frozen on dust particles.  They are 
not drops of (dirty) water until shortly before, or after they leave the 
cloud.  The temperature and air pressure are much too low there for liquid 
water to exist (down to ca. 220 K/−53.15 °C and 0.5 bar/500 hPa near the 
tropopause, according to the 1962 US Standard Atmosphere Graph; cf. NIST 
standard conditions: 293.15 K/20 °C and 1.01325 bar/1013.25 hPa).

<https://en.wikipedia.org/wiki/Atmospheric_temperature>
<http://www.wolframalpha.com/input/?i=water+phase+diagram&dataset=>

> They are larger because the vapor molecules are moving slower and more 
> nucleate (stick together) per second.

No, they can get larger because as the water *freezes* on the condensation 
nuclei, more *water* can *freeze* on the resulting ice pellets.  It is the 
same that happens when your tongue, wet with the water of the saliva, can 
get stuck on a really cold and wet piece of soft-ice cream, or your hands, 
wet with water of the skin, are stuck when touching the inside of a freezer 
[you can get severe injuries this way; kids, do not try that at home, and 
always wear thick insulating gloves when you are experimenting with dry ice 
(solid carbon dioxide)].

I strongly recommend that you read the chapters on thermodynamics of the 
Feynman Lectures on Physics, and introductory material on meteorology (such 
as what I just gave to you) to clarify some of your misconceptions about 
(water) vapor and clouds.

<http://www.feynmanlectures.caltech.edu/>

-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

Thread

Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-03 10:13 -0700
  Re: Sometimes people believe things that are nonsense Michael J. Strickland <michael06582@comcast.net> - 2016-07-06 01:33 -0400
    Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-05 23:03 -0700
    Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-06 09:59 -0700
    Re: Sometimes people believe things that are nonsense noTthaTguY <abu.kuanysh05@gmail.com> - 2016-07-06 11:15 -0700
      Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-06 18:33 -0700
    Re: Sometimes people believe things that are nonsense pcardinale@volcanomail.com - 2016-07-06 12:02 -0700
      Re: Sometimes people believe things that are nonsense noTthaTguY <abu.kuanysh05@gmail.com> - 2016-07-06 14:25 -0700
    Re: Sometimes people believe things that are nonsense Sergio <invalid@invalid.com> - 2016-07-06 14:40 -0500
      Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-07 05:51 -0700
        ah, cOOl noTthaTguY <abu.kuanysh05@gmail.com> - 2016-07-08 10:51 -0700
          Re: ah, cOOl noTthaTguY <abu.kuanysh05@gmail.com> - 2016-07-08 16:07 -0700
      Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-07 11:22 -0700
        Re: Sometimes people believe things that are nonsense pnalsing@gmail.com - 2016-07-07 18:20 -0700
          Re: Sometimes people believe things that are nonsense Sergio <invalid@invalid.com> - 2016-07-08 13:51 -0500
      Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-19 19:45 +0200
    Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-19 19:43 +0200
      Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-19 19:58 +0200
      Re: Sometimes people believe things that are nonsense Poutnik <poutnik4nntp@gmail.com> - 2016-07-19 21:48 +0200
        Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-19 22:29 +0200
          Re: Sometimes people believe things that are nonsense Odd Bodkin <bodkinodd@gmail.com> - 2016-07-19 15:33 -0500
            Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-19 22:40 +0200
              Re: Sometimes people believe things that are nonsense Poutnik <poutnik4nntp@gmail.com> - 2016-07-19 23:24 +0200
          Re: Sometimes people believe things that are nonsense Poutnik <poutnik4nntp@gmail.com> - 2016-07-19 23:15 +0200
      Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-20 09:08 -0700
        Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-21 03:27 +0200
          Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-22 20:58 -0700
            Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 07:55 +0200
              Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-23 09:21 -0700
      Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-20 12:19 -0700
        Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-21 04:58 +0200
          Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-21 05:12 +0200
          Re: Sometimes people believe things that are nonsense Poutnik <poutnik4nntp@gmail.com> - 2016-07-21 07:22 +0200
          Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-21 14:00 -0700
            Re: Sometimes people believe things that are nonsense pnalsing@gmail.com - 2016-07-21 17:46 -0700
              Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-22 08:10 -0700
            Precipitation (was: Sometimes people believe things that are nonsense) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 07:32 +0200
              Re: Precipitation (was: Sometimes people believe things that are nonsense) James McGinn <jimmcginn9@gmail.com> - 2016-07-23 08:33 -0700
                Re: Precipitation Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 21:25 +0200
                Re: Precipitation James McGinn <jimmcginn9@gmail.com> - 2016-07-23 12:38 -0700
                Re: Precipitation Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 22:01 +0200
                Re: Precipitation James McGinn <jimmcginn9@gmail.com> - 2016-07-23 18:09 -0700
                Re: Precipitation Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-24 03:53 +0200
                Re: Precipitation James McGinn <jimmcginn9@gmail.com> - 2016-07-24 06:17 -0700
                Re: Precipitation Sergio <invalid@invalid.com> - 2016-07-23 22:41 -0500
                Re: Precipitation James McGinn <jimmcginn9@gmail.com> - 2016-07-24 09:14 -0700
          Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-22 08:21 -0700
            Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 07:33 +0200
              Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-23 08:35 -0700
          Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-22 12:16 -0700
            Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 07:52 +0200
              Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-23 09:20 -0700
                Re: Sometimes people believe things that are nonsense Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 21:45 +0200
                Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-23 18:06 -0700
          Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-24 11:10 -0700
    Re: Sometimes people believe things that are nonsense Sergio <invalid@invalid.com> - 2016-07-19 18:05 -0500
      Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-07-20 11:58 -0700
        Re: Sometimes people believe things that are nonsense noTthaTguY <abu.kuanysh05@gmail.com> - 2016-07-20 15:13 -0700
          Re: Sometimes people believe things that are nonsense Sergio <invalid@invalid.com> - 2016-07-20 18:12 -0500
  Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-08-31 07:14 -0700
  Re: Sometimes people believe things that are nonsense James McGinn <jimmcginn9@gmail.com> - 2016-09-01 15:29 -0700

csiph-web