Sentences with phrase «blackbody surface»

Similarities may exist in the spectral nature of the radiation being emitted from a gas and the radiation being emitted from a differential area on a blackbody surface; but without a clearly defined surface, I don't see how Planck's blackbody radiation law can be applied.

So while, in the isothermal blackbody surface approximation, if the starting surface temperature is 288 K and we know the OLR is reduced from surface emission by 150 W / m2 via GHE, we know that removing all greenhouse agents will have a TOA forcing of -150 W / m2, (and some forcing at the tropopause, etc.) which will cool the surface temperature to about 255 K at equilibrium, absent non-Planck feedbacks.

Since the 155 W / m2 GHE is the GHE forcing based on the present climate (in the sense that removing all GH agents (only their LW opacity, keeping solar radiation properties constant) results in a forcing of -155 W / m2 at TOA for the present climate, and we know that without any GHE, in the isothermal blackbody surface approximation, the temperature will fall approximately 33 K without any non-Planck feedbacks), it can be compared to smaller climate forcings made in the context of the present climate (such as a doubling CO2.)

Not exact matches

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

The surface of the Earth radiates as a blackbody at its temperature which is continually changing because it is being heated by the sun, or it is cooling during the night.

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?

sigmaT ^ 4 is the upward blackbody radiation (based on stefan - boltzmann) at the surface, «a» is the albedo (reflectivity), so (1 - a) is the fraction of incident solar radiation that is absorbed by the planet.

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.

The emissivity of the surface in the infrared is unimportant because it behaves as though it were in a blackbody cavity in equilibrium with the lowest layers of the atmosphere.

Now, the best thing would be to be able to take your class into space and point your $ 50 sensor at the Earth from the Space Station, so you could see that the radiation going out is like a blackbody at 255K instead of the actual surface temperature of the Earth.

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

It was raised in response to an earlier theoretical proposal suggesting that certain gas - surface reactions (heterogeneous catalysis) can generate steady - state pressure gradients under low - pressure, sealed blackbody conditions.

In Kiehl and Trenberth 1997, they find a 155 W / m2 total greenhouse effect for approximately present - day Earth conditions (among the approximations: surface is a perfect (isothermal **) blackbody, and the use a representative 1 - dimensional atmospheric column (instead of seperate calculations for each location over the globe at each time over the course of a period of time sufficient to describe a climatic state — but note righthand side of p. 200, just past halfway down the column)... a few other things).

... The GHE TOA forcing of 155 W / m2 is approximatly the difference between the blackbody fluxes at 255 K and 288 K; thus if maitaining 288 K surface temperature, removing it...

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?

But the upward flux from the surface (assuming a perfect blackbody) is isotropic, which means that in order for the upward flux per unit area to fit the T ^ 4 pattern, the intensity will be anomalously small (relative to the T ^ 4 pattern) in a range of directions near vertical, and anomalously large in a range of directions closer to horizontal.

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.

Climastrologists assumed the surface of our planet to be a near blackbody that could only heat to 255K for an average of 240 w / m2 of solar radiation if there were no radiative atmosphere.

Introduction Key diagrams on the Earth's energy budget depicts an exchange of energy between the surface and the atmosphere and their subsystems considering each system as if they were blackbodies with emissivities and absorptivities of 100 % 1, 2.

A blackbody temperature at certain distance from the sun IS the Sun's surface temperature.

However, since the Earth reflects about 30 % of the incoming sunlight, the planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) is about − 18 °C, about 33 °C below the actual surface temperature of about 14 °C.

Most solid and liquid surfaces are very close to a blackbody as emitter and absorber of LWIR (that's true even for the whitest snow).

The Earth's surface temperature is 35 K warmer than its effective blackbody temperature, because of the presence of clouds and GHGs or called the natural greenhouse effect.

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

Heat radiates from the Earth's surface via thermal or (roughly) «blackbody» radiation.

It seems to me that any layer from the surface to the highest limits of the atmosphere is radiating some roughly blackbody looking spectrum corresponding to its own Temperature; and much of that spectrum exits directly to space (assuming cloudless skies for the moment) with a spectrum corresponding to the emission temperature of that surface; but now with holes in it from absorption by GHG molecules or the atmospheric gases themselves.

His non-GHG atmosphere permits the lower surface to constantly radiate to the upper surface until the two have identical temperatures in a textbook blackbody radiation calculation.

The rest of his argument is just that blackbody calculations don't produce real surface temperatures.

However blackbody calculations do not speak to high and low surface temperatures and how these are distributed over cycles in time, across surface space or throughout the atmosphere.

Its main argument is that idealized blackbody calculations did not correctly predict the Moon's surface temperatures in the 1960s because other factors besides radiative heat transfer equations actually determine real surface temperatures.

Let's look at the blackbody flux densities of objects of the temperatures we have been discussing (you can multiply by a 0.95 emissivity if you want to get to real surface values, but it doesn't matter:

If the air layer is a blackbody (ea = 1, considerable CO2), the atmosphere is Ta = 255 K (as before) and the surface is Ts = 303 K (16 K warmer than actual value of 287 K).

We vary the one free parameter, the emissivity of the atmosphere ea, but retain the surface of Earth as a blackbody with eE = 1.

So I cranked the numbers, and showed you that the radiation, even for a blackbody, of surfaces at liquid nitrogen temperatures could not exceed 2 W / m2, trivial compared to the 400 W / m2 of real surfaces at earth ambient temperatures.

Assuming a constant blackbody equilibrium temperature as seen from space, surface temperatures may still vary due to atmosphere effects.

The warmed surface radiates as a blackbody, and also loses heat through rising in air currents or evaporated moisture.

It radiates from the full extent of a dynamic 3D volume, not from some hypothetical, static (rigid) blackbody 2D surface.

In fact, anybody curious can try this: Take the surface of the sun to be 5778 K, and treat the sun as a blackbody.

A spherical cavity with a hole is an example and is «close» to a blackbody, therefore at MOST we can expect the earth to have energy densities of a black body (yes gravity complicates the actual temperature on the surface).

A blackbody at a given temperature radiates from all surfaces at a given flux.

For our thought experiment, imagine a planet the size of the Earth, a perfect blackbody, heated from the interior at 235 watts per square metre of surface area.

When we lower the emissivity of the surface from 1 (blackbody) to 0.9425 we need an increase of surface temperature of approx. 5 degress C to achieve the same level of radiation.

Now we realize that the outer part of our new smaller sphere must also absorb and radiate like a blackbody... and so on, all the way to the surface.

Ian Now we realize that the outer part of our new smaller sphere must also absorb and radiate like a blackbody... and so on, all the way to the surface.

Observations agree with climate models that a 1.2 degC rise in surface temperature produces a 2.5 W / m2 increase in OLR, not the 3.7 W / m2 increase expected for a blackbody.

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 the atmosphere (mostly N2 and O2) emitted LWIR like a blackbody, the atmospheric window readings would look like some middle atmosphere temperature — not like the surface.

Please explain why all of the planets with atmospheres (including Earth) have a surface temperature that is much higher than their blackbody temperatures.

The blackbody temperature isn't particularly relevant at a single point at the surface because there are lots of different heat transport mechanisms that affect the local surface energy balance and there's lots of thermal inertia at the surface, particularly the oceans.

6) Thus, if we assume, as a first approximation, that the Surface approximates a blackbody at 288 K, with a spectrum something like the smooth blue curve in my illustration above, we see that the Atmosphere passes the ~ 10μm region (except for part of the ~ 9.5 μm oxygen / ozone «bite») and, from the Perry plot of Surface looking UP, re-emits much of the ~ 7μm and ~ 15μm region back down to the Surface.