Atmospheric window

As atmospheric window wavelength interval of the electromagnetic radiation spectrum ( eg, visible light) is referred to in meteorology and remote sensing, for which is the Earth's atmosphere largely translucent ( transparent).

The gas mixture of the atmosphere, the air containing different gases (ozone, carbon dioxide, water vapor, etc.) that absorb the electromagnetic radiation dependent on the wavelength or scatter. That has an impact on the energy balance and consequently the temperatures on Earth. Shielding by dangerous radiation doses for life on earth and on the observability of sources of electromagnetic waves outside the atmosphere

Energy balance and greenhouse effect

The sun leads to a large thermal power by its light all emitted wavelengths of the earth. The earth in turn radiates as a black body electromagnetic waves longer wavelength again. Only a portion of the thermal radiation in the IR region of the earth can penetrate to the outside, the rest is scattered back. By this greenhouse the average temperature at the surface is higher than without the atmosphere, the temperature difference is dependent on the density and composition of the atmosphere. The most important wavelength range is shown yellow in the picture, because the 300 K warm earth radiates particularly strong here.

Absorption of UV radiation in the ozone layer

The ozone stratospheric ozone layer absorbs the short-wave UV radiation in the wavelength range below 300 nanometers almost completely, so that these high-energy UV radiation can not penetrate to the surface. This is essential for life on Earth is of great importance, since the so-called harsh UV rays are carcinogenic and mutagenic to organisms. Too high cancer rate is directly fatal for the survival of higher animal species, a too high mutation rate endangers all forms of life. Not particularly concerned Australians their skin to direct sunlight: In order to avoid these risks, set by the thinning of the ozone layer ( ozone hole see also ). Since the ozone, UV radiation between 200 and 300 nanometers completely absorbed, then this wavelength interval no atmospheric window is but an absorption band, the counterpart to the atmospheric window.

Atmospheric Windows

Wavelength intervals, which are not or hardly absorbed and scattered by the atmospheric gases is referred to as atmospheric window.

Optical window

The atmosphere is almost transparent for the range of visible light and near infrared radiation. This allows solar radiation of this wavelength range reaches the earth's surface in large quantities. These wavelengths are emitted intensively from the 5800 K hot sun. Without this atmospheric windows would not be based on photosynthetic life - as we know it - on Earth possible because no light would reach the earth's surface when in this wavelength interval, the radiation would be strongly absorbed and scattered by the molecules of the atmospheric gases.

Further, for photosynthesis less important atmospheric windows are located in the wavelength ranges of about 750 to 850 nanometers, from about 950-1100 nanometers, from about 1200 to 1300 nanometers, from about 1500 to 1700 nanometers and from about 2100 to 2400 nanometers.

Astronomical window

The optical window allows the observational astronomy observing astronomical objects in the range of visible light and the near infrared, the radio window from the observation of astronomical objects with methods of radio astronomy from the ground. The latter includes frequencies of 15 MHz to the order of 100 GHz, corresponding to wavelengths of 20 m, down to a few millimeters.