Absorption Bands and Atmospheric Windows

Some types of electromagnetic radiation easily pass through the atmosphere, while other types do not. The ability of the atmosphere to allow radiation to pass through it is referred to as its transmissivity, and varies with the wavelength/type of the radiation. The gases that comprise our atmosphere absorb radiation in certain wavelengths while allowing radiation with differing wavelengths to pass through.

The areas of the EM spectrum that are absorbed by atmospheric gases such as water vapor, carbon dioxide, and ozone are known as absorption bands. In the figure, absorption bands are represented by a low transmission value that is associated with a specific range of wavelengths.

In contrast to the absorption bands, there are areas of the electromagnetic spectrum where the atmosphere is transparent (little or no absorption of radiation) to specific wavelengths. These wavelength bands are known as atmospheric “windows” since they allow the radiation to easily pass through the atmosphere to Earth’s surface.

Most remote sensing instruments on aircraft or space-based platforms operate in one or more of these windows by making their measurements with detectors tuned to specific frequencies (wavelengths) that pass through the atmosphere. When a remote sensing instrument has a line-of-sight with an object that is reflecting sunlight or emitting heat, the instrument collects and records the radiant energy.While most remote sensing systems are designed to collect reflected radiation, some sensors, especially those on meteorological satellites, directly measure absorption phenomena, such as those associated with carbon dioxide (CO2) and other gases. The atmosphere is nearly opaque to EM radiation in part of the mid-IR and all of the far-IR regions. In the microwave region, by contrast, most of this radiation moves through unimpeded, so radar waves reach the surface (although weather radars are able to detect clouds and precipitation because they are tuned to observe backscattered radiation from liquid and ice particles).

Atmospheric Windows

Diagram of atmospheric windows—wavelengths at which electromagnetic radiation will penetrate the Earth’s atmosphere. Chemical notation (CO2, O3) indicates the gas responsible for blocking sunlight at a particular wavelength.

Source: NASA

11 Comments

  1. Fairly fine publish. My spouse and i just simply came on your current website along with wished to talk about which need truly really liked studying your own blog site content. Even so I am going to always be following for a wesite along with I really hope anyone publish once more quickly.

  2. I am therefore grateful by myself found this kind of site page. A person nearly acknowledged me personally simply exactly what We decided in order to enjoy in order to as well as then some. Exquisite posting as well as take care once again with regard to achieving the absolutely no toll!

  3. I am hence glad by myself found out the following site. You actually essentially said all of us simply just what exactly I actually elected so that you can listen so that you can plus afterward a lot of. Fabulous writing plus cheers yet again to get engaging in this virtually no fee!

  4. Hi there We are very excited We discovered this weblog, I really located you simply by accident, when We was searching upon Yahoo for something else, Regardless We are here plus We would just want to tell you thank you for a incredible post along with a all round enjoyable blog Mmm did you hear Egypt wonderful announcement

  5. I would like to thank you for the efforts youve got produced in writing this article. I am hoping the same finest operate from you inside the potential also. Actually your creative writing skills has inspired me to start my personal BlogEngine weblog now.

  6. Simply wish to say your article is as astonishing. The clearness on your submit is simply nice and i can think you’re knowledgeable on this subject. Well along with your permission let me to snatch your RSS feed to keep up to date with drawing close post. Thanks 1,000,000 and please continue the rewarding work.

Leave a Reply

Your email address will not be published. Required fields are marked *