Top-of-atmosphere
(TOA) graphs of radiation flux from earth show ‘notches’ (‘ditches’?) centered
at the nominal wavenumbers of long wavelength infrared (LWIR) active gas
molecules, mostly CO2, which do not condense in the atmosphere.
Figure 1 appears to be a typical mid-latitude TOA graph. Radiation flux intensity
is plotted vs. wavenumber at any one geometric location. Wavenumber is simply
the number of radiation wavelengths per centimeter. Wavenumber, cm-1
and wavelength in microns are easily converted: Divide 10,000 by either to get
the other.
Figure 1: Typical mid-latitude TOA emission of radiation from earth. (original graph is from NASA [1])
Areas on these
graphs represent power which for any elapsed time is energy. If there was no CO2,
the average height of the black curve between 600 and 740/cm would be
approximately 330 mW/m2 which results in an area of about 46 W/m2
while the actual area remaining is only 28 W/m2. The notches
represent, for any time increment, energy that is ‘missing’. The first law of
thermodynamics mandates that energy cannot simply disappear so where (and when)
did the energy represented by the missing 18 W/m2 go?
On average,
radiation from the liquid and solid surfaces of the earth is very closely described
by the Planck spectrum for a black body at 288 K (15° C, 59° F) (The colors you
see are reflected sunlight). The red trace on Figure 1 shows the Planck
spectrum for a black body at 294 K. Part of this radiated energy goes directly
to space through an ‘atmospheric window’ in the approximate wavenumber range
770-1230 (13-8.13 microns) where no gas molecules (except O3)
significantly absorb radiation. Over the rest of the total range of significant
terrestrial radiation (6.5-200 microns, wavenumber 1538-50 cm-1) the
radiation is absorbed by LWIR active gases (which, including water vapor, are
misleadingly called greenhouse gases (ghg)).
Logic mandates
that the elapsed time between when a molecule absorbs a photon and when it
emits one must be more than zero or there would be no indication the photon had
been absorbed. This elapsed time is called the relaxation time. Experiments [2,
3] have determined the relaxation time is longer at lower temperatures. It is
about 5 microseconds for CO2 in the atmosphere where people are.
At the scale of
atoms, the atmosphere can be visualized as molecules bouncing elastically (no
energy loss) off each other in empty space. At sea level conditions, the time
between collisions for the air molecules (molecule diameter 4E-10 m) is
extremely short, less than 0.0002 microseconds [4]. Among other properties,
these collisions are the basis for thermal conduction in the gas. Therefore,
electromagnetic radiation (EMR) energy absorbed by ghg molecules is immediately
shared with surrounding molecules both ghg and non-ghg. The sharing is thermal
conduction in the gas. The process of absorbing radiation and sharing it with
surrounding molecules is called thermalization.
A common observation of thermalization by way of water vapor
is cloudless nights cool faster and farther when absolute water vapor content
of the atmosphere is lower. Clear nights cool faster and farther in the desert
than where it is humid.
Below the tropopause (about 8 to 12 km depending mostly on
latitude) water vapor (WV) decreases from an average of about 10,000 ppmv (1%,
4% near the equator) at ground level to, because of the low temperature (about
negative 50 °C), 32 ppmv at the tropopause. Radiation from WV molecules below about
wavenumber 600/cm can only be absorbed by other WV molecules. This huge WV
molecule population gradient means that much of the outward directed radiation
from WV molecules will make it all the way to space, especially from near the
tropopause. This is demonstrated by the ‘hash’ observed in this wavenumber
range measured at the top-of-atmosphere as shown on Figure 1.
The redirection mechanism is radiation energy that is
absorbed by CO2 below the tropopause is shared with all molecules
(thermalization) and emitted to space by WV molecules.
At high altitude (above about 20 km), the remaining energy
is conducted from non-ghg molecules to ghg molecules for radiation towards
space. For lack of a better term, call the conduction of energy from non-ghg to
ghg molecules and radiated from them reverse-thermalization.
Ghg in the warmed air can emit photons only at a limited
number of wavelengths (or wavenumbers) characteristic for each molecule species.
Furthermore, all theoretically possible wavenumbers are not equally likely.
Radiance
calculated by MODTRAN6
MODTRAN6 [5] is
a computer program developed for the Airforce Research Laboratory which
(besides other things) can calculate the radiation flux at selected elevations
in the atmosphere for specified constituents and conditions. It contains
default values for several environments including the tropics and the 1976
Standard Atmosphere. Values for water vapor change rate and atmospheric
temperature vary with altitude for different latitudes and seasonal conditions
as shown in MODTRAN documentation [7].
Figures 2 and 3
are typical graphs showing how radiation flux absorbed by ghg other than WV is
redirected to WV with increasing altitude. The redirection is quantified by the
progressively increasing depth of the ‘notches’ at the characteristic
wavenumber ranges for each ghg (except WV). Note that, at 20 km redirection from
CO2 is greatest and at 50 km and higher some of the flux has returned
to the CO2 molecules. Somewhere in the vicinity of 20 km some of the
energy that has not yet radiated to space is redirected back to the CO2.
The ‘notches’
are evidence of energy redirection. Redirection is possible because of
thermalization and reverse-thermalization in the gaseous atmosphere.
Energy absorbed
by ozone begins to be significantly redirected to WV above 10 km, reaches a
maximum below 50 km and stays at the maximum level above 50 km.
Figure
3: Tropics atmosphere at MODTRAN6 default values.
Figures 2 and 3 are misleading;
especially below the tropopause. Approximately 161 W/m2 of solar
energy reaches the solid and liquid surfaces of the planet [8]. Another ~16 W/m2
is radiated from clouds through the ‘atmospheric window’ [9]. The energy
leaving the surface includes about 78 W/m2 from heat of vaporization
of water (annual rainfall averages about a meter and what comes down had to
have gone up). Another 17 W/m2 has been added by convective heat
transfer, leaving 161 + 16 – 78 – 17 = 82 W/m2 in thermal radiation.
This compares favorably to up radiation minus down radiation of 345 – 271 = 74
W/m2 at zero altitude for MODTRAN6 but is only about 73% of 382 –
269 = 113 W/m2 for MODTRAN.
With increasing altitude, the
non-radiant flux is replaced with radiant flux and the solar energy that was
absorbed by the atmosphere and clouds is incorporated. Most of this takes place
by about 10 km so the graphs at 20 km and higher should be reasonably valid.
Most of the photons emitted by the water vapor molecules are
at wavelengths different from the comparatively narrow band that CO2
molecules can absorb. Effectively, much of the terrestrial thermal radiation
energy absorbed by CO2 (and other non-condensing ghg) is
thermalized, redirected to, and radiated to space from water vapor.
At very high altitudes, temperature, molecule spacing and
time between collisions increases to where reverse-thermalization to CO2
(and O3) molecules becomes significant as does radiation from them
to space.
Figures 2 and 3
answer the question posed above of where (and when) the energy went which is
‘missing’ at the notches in TOA graphs. In Figure 1, the 18 W/m2
‘notch’ is permanently redirected to water vapor and radiated to space. The 28
W/m2 radiates to space from the 600-740 cm-1 wavenumber
range. At low altitude the tiny amount of energy absorbed by CO2 and
much greater amount absorbed by water vapor are thermalized; warming the low
altitude atmosphere.
The water vapor
content of the atmosphere diminishes rapidly as the temperature decreases with
increasing altitude. Above the tropopause it has declined to a level where
emission from water vapor ceases to dominate and emission from CO2
molecules becomes significant. The result is part of the energy which had been
redirected to water vapor at low altitude is, at high altitude, redirected back
to the wavenumber range 600-740 cm-1. The ’redirection’ is not
geometric because all wavenumbers refer to photons at essentially the same
physical location.
Energy
redirection helps explain why average global temperature tracks average global
water vapor and not CO2 [6].
References:
4. Time between
gas molecule collisions http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/frecol.html
9. Mistakes
made by the ‘consensus’: http://consensusmistakes.blogspot.com
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ReplyDeleteThis comment has been removed by the author.
DeleteMalicious nonsense.
ReplyDeleteCO2 Science - Pruitt, proof is in the pudding! Impossible Modern Marvels
https://confrontingsciencecontrarians.blogspot.com/2018/01/pruitt-proof-isin-modernmarvels.html
Your lack of engineering/science skill has made you gullible to the "malicious nonsense" group think by people with an agenda. Take the blinders off and learn what happens at the scale of molecules in the atmosphere. The molecule action mandates that CO2 has no significant effect on climate. Much more is at Ref 6.
DeleteHere is sample from the website you linked to:
Delete"Lasers wouldn't work if we had radiative physics wrong".
No one said you had radiative physics wrong. The question is whether radiative heat transfer is the dominant process in the removal of heat from our atmosphere. Your linked website makes no attempt to establish this.
Anyone who understands heat transfer phenomena is aware that radiative heat transfer is the ONLY way that heat leaves the atmosphere and goes to space.
DeleteAnd your ego has disconnected you from reality. You got words, this guy can teach you the physics http://forecast.uchicago.edu/lectures.html
ReplyDeleteand ignoring this https://confrontingsciencecontrarians.blogspot.com/2018/01/pruitt-proof-isin-modernmarvels.html - doesn't make it any less valid. Our modern marvels alone are proof that you got something very wrong.
And before calling me gullible, how about you?
Does confirmation bias mean anything to you?
You are indeed gullible and I have done my own research and challenge it. My only interest is reality and in fact believed CO2 was the culprit until proven otherwise.
DeleteListening to people like in your link contributes to your lack of understanding. I saw no mention of thermalization. Thermalization results from the fact that the porbability of absorbed radiation energy being shared with other molecules is thousands of times more likely than the molecule that absorbed the photon will emit a photon.
No mention of the vapor pressure of water. Unfortunately, many so-called experts appear to be unaware water has a vapor pressure that depends only on the temperature of the liquid water.
Implication that atmospheric water vapor depends only on air temperature which would require that it rains everywhere all the time.
And, no explanation for the 'notch' in graphs of TOA radiation flux.
A simple demonstration of misinformation in that series is the assertion that water vapor is essentially constant. It has been increasing 1.5% per decade for at least 30 years. Measured and reported by NASA/RSS it is graphed as Figure 3 in my Ref 6 link.
If you care to actually learn about this stuff spend some time with the link at Ref 6. Otherwise, I can't help you.