More thermodynamics of the Flood.
>From: "Allen Roy" <allen@infomagic.com>
>To: <asa@calvin.edu>
>Subject: Re: craters (part of YEC defined)
>Date: Wed, 17 Mar 1999 21:10:42 -0700
>
>> From: Adam Crowl <qraal@hotmail.com>
>> >From: "Allen Roy" <allen@infomagic.com>
>> >It seems to me that a goodly portion of the energy would be lost
into
>> >space. The path of least resistance is upward away from the planet.
>> Heat is lost, from a planet, via radiation and the rate of loss
depends
>> on the optical thickness of the atmosphere and the temperature of the
>> surface doing the radiating.
>
>According to Strahler and Strahler, "Modern Physical Geography," 1987,
pg
>60, 68% of solar (shortwave, i.e., light) energy that strikes the
earth
>per year is absorbed by the atmosphere (15%), clouds (3%) and the
ground
>(50%). (Ground includeds water surfaces.) The atmosphere and ground
both
>act as heat storage devices.
>
They'll only store energy at the relevant equilibrium temperature - if
they're higher they'll lose that heat as radiation.
>> With all the vulcanism and cosmic debris
>> raining down the atmosphere would be optically thick and very likely
>> things would be a lot hotter than at present due to the resulting
>> greenhouse effect.
>
>Optical opacity may not affect longwave radiation. But even if the
>atmosphere became opaque or translucient to longwave radiation and
absorbed
>all the longwave radiation from the ground, the longwave energy
absorbed by
>the atmosphere would only increase from 90% to 98% of the total solar
input
>energy (an increase of only 10%). The average temperature of the
>atmosphere might increase by about 10%.
>
Venus' surface radiates at a temperature about three times higher than
its equilibrium temperature with the radiation that reaches it from the
Sun. Why? Because it's only at that temperature that enough energy
escapes in the "gaps" in the greenhouse blanket to match the input.
Remember the curve from Planck's temperature equation - if all that
escapes is long-wave then not enough will escape to balance the input at
just 244 K [Venus' equilibrium temperature after taking into account
albedo.] At that temp the peak is in the infra-red, but it can't escape
in sufficient quantities to do the job - it gets "reflected back" at the
ground, raising the surface temp even higher. Eventually enough escapes
as the temp rises to balance the books but by that stage Venus' surface
temp is 750 K!
Similar situation on Earth, but with a thin greenhouse, so the temp
increase is only ~ 33 K.
>A catastrophe would introduce energy into the system, some of which
would
>be absorbed by the ground and some by the atmosphere. In the case of a
>large asteroid explosion, some of the energy would escape directly into
>space after blowing a huge hole out of the atmosphere. So far I have
not
>found useful information that would relate this additional energy to
the
>global energy ballance, but I'm still looking.
>
>
>> >You hear of how Noah and Family would be broiled alive in extreme
>> >temperatures. But where is the calculations of corresponding heat
loss
>> >into space?
>> The point is the output goes up, but only with the average
temperature.
>> To lose heat rapidly it has to be really, really hot!
>
>Not so, because you are not considering the direct longwave radiation
from
>the atmosphere itself, which is the where the major porition of heat
loss
>to space comes from.
>
As I explained I have. That long-wave only goes up with the temperature
of the source, and only slowly for the relevant frequecies.
>Like I said before, where are the calculations on heat loss to space.
None
>that I have seen consider radiation from the atmosphere itself.
>
But they all do in greenhouse calculations, that's what optical depth
calculations usually involve...
>
>You are right that water vapor and CO2 in the atmosphere absorb heat.
But
>unless they impede direct longwave radiation from the atmosphere, they
>won't reduce the rate of heat loss by the atmosphere directly into
space.
>The would just increase the quantitiy of heat which the atmosphere
could
>store.
>
Increase the heat store yes, but as I explained the longwave is only as
intense as the temperature will allow. It has to be real hot for enough
to escape on Venus, and it wouldn't be much cooler here on Earth.
>Another thing to consider is that any optical transluciency of the
>atmosphere would greatly reduce the amount of energy absorbed by the
>ground. Normally 50% of the incoming solar shortwave (light) radiation
is
>absorbed by the ground. Another 32% is reflected by scatter, clouds
and
>the ground. Reflection would likely increase due to dust particles in
the
>high atmosphere. And, 18% is absorbed by the atmosphere and clouds.
>Absorption is likely to increase also because of the dust particles.
>50+32+18=100%
>
>One might expect to see reflection increase from 32% up to 35 to 40%.
>Atmospheric absorption may increase from 18% up to 20 to 25%. Thus we
may
>reduce the radiation absorbed by the ground from 50% down to 45 to 35%.
>This would greatly reduce the amount of heat converted from the
absorbed
>shortwave energy to be radiated into the atmosphere.
>
>Thus an increase in air temperature due to longwave opacity would be
offset
>by loss of absorbed shortwave energy because of dust in the atmosphere.
>The net result would not be the run-away hot-house you have described.
>
I'd say it would. We're also talking heat inputs from surface sources -
vulcanism, heat from all those impacts etc. With enough water vapour up
in the air the greenhouse will rise in effect. Question is just how much
would be thrown up as vapour by the lava and the impacts. Also the
motion of the continents requires immense amounts of ocean floor to be
generated, and that'd be extremely hot lava - to add to all the
continental vulcanism, and invasive plutonism that's going on. The
equilibrium state of the Earth would be hard to calculate precisely, but
all we need is ~ +323 K to kill everything other than bacteria.
>I am still researching how fast the system could adjust to changes.
>
Slowly maybe. Not fast enough to save Noah.
Adam
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