Modified blackbody model of earth. What is wrong with it?

Asked by: Mark Odom

Does it seem reasonable that the earth’s atmosphere will allow the blackbody radiation to pass?

NO.



It is a result of warming of the Earth’s surface by the absorption and re-emission of IR radiation by molecules in the atmosphere.

Is the Earth’s atmosphere a blackbody?

The Earth’s atmosphere cannot be treated as a blackbody.

What happens with the temperature of the earth if the emissivity of the atmosphere increases?

An increase in atmospheric emissivity produces an increase in the surface temperature of the Earth.

What is the emissivity of Earth?

between approximately 0.6 and 1.0

The emissivity of most natural Earth surfaces is a unitless quantity and ranges between approximately 0.6 and 1.0, but surfaces with emissivities less than 0.85 are typically restricted to deserts and semi-arid areas. Vegetation, water and ice have high emissivities above 0.95 in the thermal infrared wavelength range.

Why is Earth not a perfect blackbody?

The deviation from a perfect blackbody spectrum is due to many factors, including the absorption of light by constituents of the solar atmosphere, and the fact that the photosphere is not uniform, but has some hotter and some cooler regions, so that what is seen from Earth is a composite spectrum of blackbody radiators

Does Earth’s surface emit blackbody radiation?

Most of the Sun’s radiation is blackbody radiation radiated from the Sun’s surface, or photosphere, whose temperature is about 5700 K. Earth’s surface is warmed by absorbing this light. At the same time it is absorbing energy, Earth’s surface is emitting its own blackbody radiation.

What is the blackbody temperature of Earth?

The surface radiation emission, 396 W·m^–2, is the energy flux calculated from the Stefan-Boltzmann equation for a black body at a temperature of 288 K, the observed average surface temperature of the Earth.

Is everything a blackbody?

All objects are black body radiators, as all objects emit electromagnetic radiation according to their temperature. A few common day examples of black body radiators which utilize their radiation for other processes or emit visible light are: Stoves.

How does blackbody radiation affect climate change?

While blackbodies emit radiation over all wavelengths, a significant fraction of their emitted energy is concentrated in a limited range of wavelengths. The wavelength corresponding to the peak intensity of emission decreases with increasing temperature.

Why does temperature increase as emissivity increases?

Yes, Emissivity changes with temperature because of energy that is tied up in the behavior of the molecules that form the surface. Following Plancks law, the total energy radiated increases with temperature while the peak of the emission spectrum shifts to shorter wavelengths.

What factors affect emissivity?

The emissivity also depends on the temperature of the surface as well as wavelength and angle. Knowledge of surface emissivity is important both for accurate non-contact temperature measurement and for heat transfer calculations. Radiation thermometers detect the thermal radiation emitted by a surface.

Why is the temperature on the Earth’s surface not the same everywhere?

The answer is due to uneven heating of the Earth by the sun. The Earth is a sphere, and so is the sun. When the earth orbits the sun, the center of the Earth gets more direct sunlight than the poles.

Is Earth a perfect blackbody?

Although a blackbody does not really exist, we will consider the planets and stars (including the earth and the sun) as blackbodies. Even though by definition, they are not perfect blackbodies, for the sake of understanding and simplicity we can apply the characteristics of blackbodies to them.

Why classical physics Cannot explain blackbody radiation?

But classical physics could not explain the shape of the blackbody spectrum. The electrons in a hot object can vibrate with a range of frequencies, ranging from very few vibrations per second to a huge number of vibrations per second. In fact, there is no limit to how great the frequency can be.

Why is the blackbody temperature of the earth much colder than the Earth’s actual surface temperature?

The surface temperature of the earth is higher than its black body temperature owing to the presence of a few principally triatomic species, notably water vapor, carbon dioxide and ozone.

How does a greenhouse gas effect the earth blackbody radiation spectrum?

As the concentration of greenhouse gases are increased, more of Earth’s electromagnetic infrared radiation is absorbed by the atmosphere, making the atmosphere warmer. A warmer atmosphere radiates more effectively, resulting in an increased re-radiation of infrared photons from the atmosphere to Earth’s surface.

What atmospheric gases will absorb infrared light?

Water vapor, carbon dioxide, methane, and other trace gases in Earth’s atmosphere absorb the longer wavelengths of outgoing infrared radiation from Earth’s surface.

Why is the Stefan Boltzmann law important?

The Stefan-Boltzmann Law explains how much power the Sun gives off given its temperature (or allows scientists to figure out how hot the sun is based on how much power strikes the Earth in a square metre). The law also predicts how much heat the Earth radiates into space.

What spheres are zones of Earth’s atmosphere?

Earth’s Atmosphere: A Multi-layered Cake

• Troposphere. Earth’s troposphere extends from Earth’s surface to, on average, about 12 kilometers (7.5 miles) in height, with its height lower at Earth’s poles and higher at the equator. …
• Stratosphere. …
• Mesosphere. …
• Thermosphere. …
• Exosphere. …
• The Edge of Outer Space.

Do humans live in the troposphere?

Troposphere. The troposphere is the lowest layer of our atmosphere. Starting at ground level, it extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level. We humans live in the troposphere, and nearly all weather occurs in this lowest layer.

In which layer of the atmosphere do humans live?

The Troposphere



This is the layer we live in and contains most of what we consider to be “the atmosphere,” including the air we breathe and nearly all of the weather and clouds we see. In the troposphere, the temperature of the air decreases the higher you go.