Sentences with phrase «n blackbody»

Finally if I am not mistaken the temperature of the top layer of an atmosphere consisting of n blackbody shells should be Tg / -LRB-(n +1) **.25) not Tg / (2.

[Response: The Earth is not a blackbody.

If a sidewalk was the mythical blackbody it would do this - but it's a sidewalk not a blackbody.

[1] But this is an erroneous assumption because the Earth and its subsystems are not blackbodies, but gray - bodies.

But this is an erroneous assumption because the Earth and its subsystems are not blackbodies, but gray - bodies.

Fine, if it isn't blackbody, what is it?

That is not a blackbody and it means that the dT response of the ocean or any frequently wetted surface is not the same as a blackbody response.

If CO2 absorbs at 15 micron, it also emits at 15 micron (not a blackbody distribution of all wavelengths based on atmospheric temperature).

As others have pointed out, excluding clouds, the average reflectivity of earth's surface is about 0.124 Earth is not a blackbody, most of the earth is covered by ocean, which has an emissivity between 0.92 and 0.96 - I'll use a 0.94 average.

The Earth is not a blackbody and the absorptivity measured with appropiate technology gave a result of 0.82.

Which introduces emissivity because the Earth is not a blackbody (which don't exist) and has a limited absorptivity.

Not exact matches

[Response: If the Earth was a blackbody, the surface temperature would be 255K (so therefore it can't be).

His carefully considered response to the techinical issues raised here: «I received emails saying I'd wrongly assumed the Earth was a «blackbody» with no greenhouse effect at all (I hadn't).

Moreover the radiation from the greenhouse gases is calculated using Planck's function for blackbody radiation, but greenhouse gas molecules emit lines, not contiuous radiation.

They were able to combine their data with observations from other telescopes and revealed an almost featureless spectrum that could not be completely explained by a blackbody model (blackbodies are opaque objects that emit thermal radiation).

Our results suggest that the size of the smooth cloud, a dominant component in the model, is by about 10 % more compact than previously thought, and that the dust sizes are not large enough to emit blackbody radiation in the mid-IR.

Request for clarification from a retired engineer: when it's said that methane is N times the greenhouse gas that CO2 is, is that purely taking into account their absorption spectra relative to the blackbody emission from the surface, or does it take into account saturation as well, since methane constitutes a much smaller percentage wrt CO2?

I am not saying the atmosphere is like the n - blackbody shell atmosphere.

Moreover the radiation from the greenhouse gases is calculated using Planck's function for blackbody radiation, but greenhouse gas molecules emit lines, not contiuous radiation.

One extremely slight complaint: During my second attempt at the exam for the first lecture, I got a question about blackbody radiation, which hadn't been addressed during the filmed lecture.

Indeed, you can not get 33 degrees of warming over and above the blackbody temperature without positive feedback.

The work is an estimate of the global average based on a single - column, time - average model of the atmosphere and surface (with some approximations — e.g. the surface is not truly a perfect blackbody in the LW (long - wave) portion of the spectrum (the wavelengths dominated by terrestrial / atmospheric emission, as opposed to SW radiation, dominated by solar radiation), but it can give you a pretty good idea of things (fig 1 shows a spectrum of radiation to space); there is also some comparison to actual measurements.

David@288, I'm just going with physics, and I don't see how you get enough negative feedback to get a negative sensitivity AND get 33 degrees of warming over Earth's blackbody temperature.

David Benson, Based solely on the fact that Earth was 33 degrees warmer than its blackbody temperature, on what was known of the absorption spectrum of CO2 and on the fact that Earth's climate did not exhibit exceptional stability characteristic of systems with negative feedback, I'd probably still go with restricting CO2 sensitivity to 0 to + infinity.

[Response: If the Earth was a blackbody, the surface temperature would be 255K (so therefore it can't be).

If I use the Planck function in the context of polarized radiation, assume if I don't otherwise specify it, that it is the original Planck function (monochromatic blackbody intensity as a function of temprature) divided by some value that represents the range of polarizations, so that it is an intensity per unit of the polarization spectrum.

More to the point though, CO2 (or H2O or whatever) absorption of IR radiation does not depend on the earth's blackbody or brightness temperature being higher than the mean temperature of the atmosphere (and the CO2).

Refraction, specifically the real component of refraction n (describes bending of rays, wavelength changes relative to a vacuum, affects blackbody fluxes and intensities — as opposed to the imaginary component, which is related to absorption and emission) is relatively unimportant to shaping radiant fluxes through the atmosphere on Earth (except on the small scale processes where it (along with difraction, reflection) gives rise to scattering, particularly of solar radiation — in that case, the effect on the larger scale can be described by scattering properties, the emergent behavior).

Depending on the lapse rate in the stratosphere, the hill in the downward flux could reverse at some point, particularly if their is a large negative lapse rate in the base of the stratosphere — but I don't think this tends to be the case; anyway, let's assume that the CO2 valley in the TRPP net upward flux only deepens until it saturates at zero (it saturates at zero because at that point the upward and downward spectral fluxes at the center of the band are equal to the blackbody value for the temperature at TRPP).

So the intensity of radiation (at some frequency and polarization) changes over distance, such that, in the direction the intensity is going, it is always approaching the blackbody value (Planck function) for the local temperature; it approaches this quickly if the absorption cross section density is high; if the cross section density is very high and the temperature doesn't vary much over distance, the intensity may be nearly equal to the Planck function for that location; otherwise its value is a weighted average of the Planck function of local temperature extending back over the path in the direction it came from.

Although that will be true in the mid atmosphere, do you agree that is not the case near the surface of the Earth where the greenhouse molecules are being excited by blackbody radiation from the Earth's surface, but are being relaxed by collisions with other air molecules such as N2 & O2?

In that case, while holding temperatures constant and non-photon material at LTE, along a path, absent scattering and reflection, the intensity is always tending to approach the local blackbody value; it will not actually reach the blackbody value if the temperature varies along the path with the same tendency.

The blackbody intensity varies as a function of n in the same way.

Planck function / blackbody radiation vs radiation from molecules, matter: the physical processes are not the same and do not follow the same unfettered rules.

His carefully considered response to the techinical issues raised here: «I received emails saying I'd wrongly assumed the Earth was a «blackbody» with no greenhouse effect at all (I hadn't).

Why not start with a pure theoritical 24 hour rotating blackbody with 1/2 recieving full spectrum 1370 watts, from an object of approximately 30 arc min.

Except for: — Your claims that bidirectional EM violates the 2nd law of thermodynamics; — Your sentient detector that received no energy from the object it is pointed at but radiates energy according to the temperature it is point at allowing you to see beyond the edge of the observable universe (Still awaiting the Nobel prize for that one no doubt); — Your perfectly radiating blackbody that does not radiate according to its temperature; — Your claims EM energy interferes which prevents energy from a colder body reaching a warmer one — a concept which would mean it would be impossible to see your reflection in a mirror.

«I've yet to find a single one that supports your claim the EM does not travel in opposing directions; that a blackbody does not radiate EM energy according to its temperature.»

It can not and does not emit a continuous blackbody spectrum.

The entire atmosphere surface to 100 km edge of space is already much much warmer than 193K, and a true or «partial» blackbody at 193K can not warm a much warmer blackbody at 255K or 288K.

So Earth is not even nearly a perfect blackbody.

Or said differently if want to say Earth uniform temperature is about 5 C, this is fine - close enough - as long as you don't think this means Earth's average temperature is about 5 C. Or if want a real science, it's a bad idea to playing around with fictitious blackbodies.

But it's different story with solids [or liquids]- they can reflect but don't emit «higher temperature» unless they are at a higher temperature [see, blackbody temperature].

The fictional material envisioned as a blackbody doesn't imagine that any blackbody includes any specific attribute of it's heat capacity.

But this does not apply to a spherical blackbody [assuming you could make such a thing].

Earth does not in any way resemble a spherical blackbody.

Painting the sidewalk black would help, but it still doesn't make it a blackbody.

The Stefan - Boltzmann is NOT an appropriate equation to perform the calculations used in climate science — ONLY Planck's equation completely describes blackbody emissions.

Technically, only the surface needs to be a blackbody... It does not look like a well - posed problem to me.

It is, effectively, at the blackbody radiation temperature (and all molecules including N2 and O2 absorb and emit blackbody radiation — this seems to not be understood by many).