A dialog:
- You know, there is not any atmospheric greenhouse warming on Earth's surface...
"What? Not any greenhouse warming ???
"The Earth is warmer than Moon, because of the atmosphere - don't you know that?
It is the atmosphere that keeps Earth warm! "
- Earth's atmosphere is very thin and transparent - it doesn't keep Earth warm. It is the Rotational Warming Phenomenon which makes Earth warmer than Moon.
"Very strange - because everyone knows - it is the atmosphere what keeps Earth warm. Now you are saying..."
- Earth rotates much faster than Moon. This is basical for the Rotational Warming.
"The rotation causes some friction... It is the nuttiest thing I ever heard!"
- It is not friction, it is the interaction with solar energy that is different when planet rotates faster.
"So it is not friction. What is it then? It is a very STRANGE THEORY, what does it mean? And what is the use of it?"
- The first thing is that Earth is WARMER than Moon, because Earth has a higher (N*cp) product.
Where:
N - the spin (rotations/day)
cp - the average surface specific heat (cal/gr*oC)
"People need to have an explanation AS SIMPLE AS POSSIBLE."
- Well, Earth is warmer than Moon, because Earth ROTATES FASTER, and also because Earth is COVERED WITH WATER.
"Still very strange. It is said, NO MATTER how fast a planet or moon rotates, the rate of rotation DOESN'T AFFECT the amounts of absorbed heat."
- What actually happens, is that a planet or moon surface with a higher (N*cp) product ABSORBS LARGER amounts of heat.
"Why so? The incident solar energy (lessened by Albedo) IS THE SAME, no matter the rotation rate."
- Yes, the incident solar energy IS THE SAME, but the amounts of absorbed heat are not. The half of a planet surface is always solar lit. But the energy absorbed in - it DEPENDS on the surface's (N*cp) product. The higher the (N*cp) - the more of the incident solar energy absorbed.
"And WHERE DOES GO the not absorbed solar energy then?"
- Yes, the not absorbed solar energy - when it is not able - when there is not enough time - when there is not enough space, and it is not able to proceed into inner layers and to get absorbed as heat there, IT IS INEVITABLE then, for that energy to be IR emitted out.
Because the solar radiative energy is not of a kind to wait in the line till surface favors to absorb.
"IT WAS ALWAYS SAID, and it was always meant, that when solar energy hitting the surface, solar energy gets first absorbed in as heat, and only then it gets IR emitted."
- Yes, it was considered so. But radiative energy is not heat "per ce". When hitting surface while getting transformed into heat, it INDUCES the surface skin layer's high temperature.
If not capable to entirely get in by the conduction, some of energy inevitably gets "pushed" AWAY as radiative IR emission.
Thus at the point A LOCAL INSTANTANEOUS EQUILIBRIUM occurs. Some energy is SW reflected, some is conducted in (absorbed as heat), and some is emitted out as IR.
"Let’s say you are right and the average planetary temperature increases with rotation. That means that when I compare a slow-rotating planet to a
fast-rotating planet, the fast-rotating planet has a higher temperature. That means the fast-rotating planet is radiating more energy than a slow-rotating planet. WHERE DOES THE ADDITIONAL ENERGY COMES FROM? It’s not coming from the rotation the planet."
- The faster rotating planet is warmer, yes - but it doesn't emit more energy - because the energy is from sun, and it is always the same, no matter how fast a planet or moon rotates.
Here it is what actually happens. The faster rotating planet emits THE SAME AMOUNT of energy as the slower one. But the faster rotating planet is warmer, because it absorbs MORE ENERGY AS HEAT, than the slower rotating one.
The faster rotation rises the average surface temperature - so it makes a planet or moon warmer.
But planets and moons do not emit at their average surface temperatures.
Because average temperature is not a temperature per ce !!!
"Ok, I understand that. But there is a physical limit to how much a faster rotation can warm a planet. At a maximum, if all the temperature swings were perfectly evened out, we can only get back to Stefan-Boltzmann (S-B) effective temperature, not above it."
- At first let's make it clear - no matter how fast the rotation, a planet is always irradiated from one side only. Thus the temperatures never can be evened out.
But as theoretical approach - the perfectly evened out surface temperatures - it makes sense, but there is an apparent physical issue.
The Stefan-Boltzmann (S-B) theoretical effective temperature (Te) does not pose any mathematical constraint on planets and moons temperature rise. Because the S-B equation is not applicable on planets and moons average surface temperatures comparison, it is not applicable because of an apparent physical issue.
Let's explain,
The S-B theoretical effective temperature is defined as the temperature of a black body that would emit the same total amount of electromagnetic radiation that is fallen upon it.
And to be more correct though, Stefan-Boltzmann emission law equation
M = σT⁴ (W/m²)
doesn't say about the blackbody temperature being determined by electromagnetic radiation that is fallen upon it.
The effective temperature (Te) was only later defined for stars emitting from their inner source of energy,
by taking the fourth root of by stars emitted flux,
Te = ( M /σ )¹∕ ⁴ (K)
and it was mistakenly extended to planets and moons, which emitt IR, but their temperatures do not relay on the inner sources, because they are well insulated by their crust, so their respective IR emission, can be said with confidence, originates from the incident solar energy.
But, what is fallen upon them - the not reflected portion of incident SW solar energy -
it IS NOT EXPECTED to get absorbed entirely as heat in inner layers.
Therefore not the entire not reflected amount of electromagnetic radiation that is fallen upon planet or moon participates in surface energy distribution, when in comparison with effective temperature equation (Te), because it is not all of it absorbed in inner layers.
That is why when rotating faster, planets and moons are warmer, because they are able THEN to absorb LARGER quantities.
"The slower rotation - the higher the temperature swings. The faster rotation makes temperatures more even - it results to higher average surface temperatures. But the amount of energy absorbed as heat and energy emitted as IR - when planet is in equilibrium - it is always the same."
- Yes, the energy emitted as IR - when planet is in equilibrium - it is always the same. And the faster rotation makes temperatures more even - that's right too...
The faster rotation also makes planets absorb in more energy as heat. It is the way the faster rotating planets achieving their more even surface temperatures distribution.
When in equilibrium, that additional heat is also IR emitted - in a different by equally balanced (energy in = energy out) pattern.
So the energy balance equation writes as:
not reflected incident SW energy = (not absorbed as heat outgoing IR) + (absorbed as heat outgoing IR)
When faster rotating, planets achieve a more even surface temperatures distribution - it is a continuous process - a higher heat absorption-emission pattern results to the more even surface temperatures distribution.
Planets and moons are not the already unevenly warmed, or having unevenly distributed inner heat sources.
Planets and moons continuous interaction with the solar incident energy is what formulates their respective uneven surface temperatures distributions. It is a continuous PROCESS.
Thus, the faster rotating planets and moons always absorb more heat, because it is the way for the balanced emitting out.
"Does that mean there can be two planets at the same distance from the sun, emitting the same IR outgoing energy, but having different average surface temperatures? Does it really happen?"
- We have demonstrated further on below, - planets and moons with very DIFFERENT AVERAGE TEMPERATURES, may emit the same amounts IR energy.
Also, planets and moons with the SAME AVERAGE TEMPERATURE, may emit very different amounts IR energy.
"So what’s going on? Does this mean that the S-B equation is incorrect, or that it doesn’t apply to the planets?"
- Planets and moons average surface temperatures are not uniform surface temperatures, The average temperature is not a measure of emittancy. Planets and moons DO NOT EMIT at average temperatures.
"The average temperature doesn’t matter. What only matters is the average radiation."
- Planets and moons ARE NOT BLACK-BODIES. Black-bodies are previously warmed to certain uniform temperature, or they have inner sources of heat in thermal equilibrium with their emitting surface.
"The radiation is proportional to the fourth power of temperature. This means when the temperature is high, there is much more radiation,"
- Planets and moons solar lit side is in INTERACTION PROCESS with incident solar flux. The surfaces develop at the point a local instantaneous energy-equilibrium. Some energy is SW reflected, some is conducted in (absorbed as heat), and some is emitted out as IR.
Also, there should be added, that at the point the local temperature induced is in a necessary accordance with that instantaneous energy-equilibrium.
When not solar irradiated, when in the dark, planets and moons surfaces IR emission is much lower.
"Why then the Earth’s temperature is well above the S-B theoretical temperature of ~ -18°C?"
- Because the S-B theoretical temperature does not pose a mathematical constraint.
The S-B theoretical temperature is not applicable on planets and moons, because the S-B theoretical temperature mistakenly assumes planets and moons absorb in form of heat the entire not reflected solar energy.
But actually they absorb in form of heat only a fraction.
Important:
The faster rotating planet is warmer, because it absorbs more heat at SOLAR LIT HEMISPHERE, than the slower rotating one.
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The discovery strengthens not only research on Planetary Temperature, but also the science of physics in general. The methods developed open avenues for other physical discoveries.
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