# Tag Info

38

Water has lowest EM absorption in the blue part of light spectrum and increases rapidly towards both UV and red parts of spectrum. As a result in visible light water is blue. Same goes for the ice as it has very similar absorption spectrum. While there is a lot of white in the picture, all of it is a thin snow cover on top of blue ice. Once the snow ...

28

Absolutely not. While the answers by casey and farrenthorpe correctly state that the blue color is due to Rayleigh scattering, the composition of the atmosphere varies considerably from place to place - and with different composition come different degrees of scattering, and different color / intensity. Typically regions of greater industrial activity will ...

18

Fair weather cumulus clouds are white because there is a clear path for sunlight to reflect off the cloud and into your eye. Even when there are many of them, they are not vertically developed and photons can still scatter off of them to you. As cumulus develop into towering cumulus and cumulonimbus they become horizontally widespread and quite high (the ...

16

"Transparent" is not the same as "white" : white bodies reflect most of the light while transparent bodies let the light though. Once the light enters into water, it may need to travel a long way before it has a chance to go out, and that long travel path provides more opportunities for absorption. Water absorbs light by itself much more than snow, but ...

15

The blue color of the sky is due to Rayleigh scattering. As light from the sun shines down it scatters off of (mostly) nitrogen molecules in the atmosphere. Without this process, the sky would be dark during the day except for the bright sun, moon, and stars. Rayleigh scattering is more efficient for shorter wavelengths. So, even though the Sun ...

14

To supplement farrenthorpe's answer, the color of the sky will be a function of the path length between the top of atmosphere and your eye along the path from the sun to you. Due to Rayleigh scattering, shorter wavelengths will scatter before longer ones. As the path length increases more of the longer wavelengths will be scattered. The color of the sky ...

14

Disclamer: I am not an atmospheric or climate scientist; corrections are welcome if I have anything wrong. Human heat production According to the IEA, world primary energy consumption in 2012 was 13370 million tons of oil equivalent, which works out to being $5.6 \times 10^{20}$ Joules. Averaged over a year, this equates to $17.8\,\mathrm{TW}$. Wind, solar,...

12

I had a very similar question in a job interview! The only difference is that it was an image from SEVIRI on Meteosat. The imager on HIMAWARI is called the Advanced Himawari Imager (AHI). The AHI IR1 channel is actually channel 13 with a central wavelength of 10.4 µm, which is in the window region (apparently it's called IR1 in reference to an older ...

12

Basically, we can ignore the heat we release compared to the effect of the $\ce{CO2}$ we release. To be more specific: Heat we release has only a temporary effect because heat is radiating out to space. In fact you can get an idea of how long it takes for newly released heat to radiate away by checking how quickly temperatures drop when the sun sets. It'...

11

The two articles you found are spot-on. An isothermal atmosphere is indeed the condition that maximizes entropy for a given amount of energy. Yet a positive lapse rate is almost always observed. Temperature typically decreases with increasing altitude. The key to resolving this apparent paradox is how heat flows into and through the Earth's atmosphere. The ...

11

It is likely because there is already a conversion from the raw data to the grayscale image posted on the CWB website. From this online course (emphasis mine): [...] using the mathematics behind the laws of radiation, computers can convert the amount of infrared radiation received by the satellite to a temperature (formally called a "brightness ...

5

It is not an easy problem even for a simple object. The temperature will vary as the conditions change, but the usual approach to such problems is to find the equilibrium temperature for a set of conditions. This is, to find the final temperature that the object will reach if exposed to a given solar irradiation, with air at a given temperature, for given ...

4

That +2.2 W/m2 is the effective radiative forcing, which is the difference in net top of atmosphere radiation in response to a changed set of conditions (e.g., greenhouse gas and aerosol concentrations, land use) after allowing fast system feedbacks to equilibrate (e.g., tropospheric humidity, stratospheric cooling) but not allowing for slow system feedbacks ...

4

A body has to emit as much thermal energy as it absobs to remain in thermal equilibrium. The Earth has been doing the same since its formation, i.e, it absorbs solar shorwave radiation by its atmosphere, solid earth and water body, and releases it in the form of longwave radiation. The amount that is released has to be equal to the amount that is absorbed ...

4

It depends on the wavelength. The figure shows the most absorbing species between 6 and 16 µm for a U.S. standard tropical atmosphere (Note: this figure does NOT include the Earth's surface!). Absorption data is taken from Anderson et. al (1986) and simulations are performed with the open-source Atmospheric Radiative Transfer Simulator (ARTS; Eriksson et ...

3

Q: What radiates energy back into space? A: anything above absolute zero temperature. That is, absolutely everything, according to the Stephan-Boltzman's law: $$W = \sigma T^4$$ Where $\sigma$ is the Stephan-Boltzman constant and $T$ is the absolute temperature. So of course, volcanoes, steel foundries, forest fires, etc emit a disproportionate amount of ...

3

What is most mysterious to me, what is the 'factor' of infra-red production by different surface materials. In asking about different surface materials, you are missing the big picture. If you want to understand global warming, simply look at the big picture you provided in the question. The Earth's surface receives more than twice as much energy in the ...

2

Water (solid or liquid) has some absorbtion. It is rather low for pure water for visible or near-visible light and that's why water it is considered transparent. But only to an extent - few meters of water look blue and few hundred meters look black, esp. if you are UNDER those few hundred meters. Then we have snow. Snow has an abundance of optical ...

2

The premise that the Stefan-Boltzmann equation is used for greenhouse gases is wrong. The Stefan-Boltzmann equation is used for irradiance output, not energy input. The ground warms the atmosphere, and the atmosphere releases energy into space. I suggest looking at the one-dimensional energy balance model. See http://kurs.uib.no/acdc/filer/219.BYQINh.pdf

2

The yearly average Top Of Atmosphere (TOA) Outgoing Longwave Radiation (OLR) is around 145–345 W/m², as measured by the AIRS instrument: Source: Wikimedia Commons contributors, "File:AIRS OLR.png," Wikimedia Commons, the free media repository. Now, this is an average that includes both day and night. How much does it vary? This depends on the location. ...

2

The hotter the Earth gets the more it re-radiates energy back into space.You can see a tiny fraction of this energy by looking at the new moon. The feint glow is just a small part of the re-radiated spectrum. The long term differential between incoming and outgoing energy is what is causing global warming. It isn't 'a few degrees (Centigrade) every year'. ...

2

Beam radiation is direct radiation, e.g. photons that have not been scattered. Diffuse radiation is indirect and has been scattered. Examples of beam radiation from the sky would be from the sun directly to your eye. Diffuse solar radiation would be the blue sky (scattered out of the direct beam by the atmosphere), clouds and anything you can see that is ...

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