Interactions of Electromagnetic Radiation with Atmosphere: Absorption, Scattering, Transmi, Slides of Geology

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Movement of EMR in the

atmosphere and

Atmospheric Window

Sumo Ranjan Mandal Enrollment no. CUSB

Interaction of atmosphere and

electromagnetic radiation

 Before the Sun's radiation reaches the Earth's surface, three interactions in the atmosphere happen which are relevant to remote sensing.  Absorption  Scattering  Transmission

Interaction of earth surface

and electromagnetic radiation.

After EMR passes through atmosphere two phenomena takes place. 

1. Reflection 
2. Refraction

Reflection and Refraction

Reflection; The return of the light/sound/heat after hitting the surface. Energy that has transmitted the atmosphere gets reflected by hitting on the surface and return to the sensor.  (^) Refraction; The bending of light(also sound and other waves) as is transferred from one medium to another medium. Energy coming from air get refracted when it passes through the liquid medium (water bodies on earth). After above events, the energy behaves same as it was behaving during its arrival to earth through atmosphere.

atmospheric window

 An atmospheric window is the portion of the electromagnetic spectrum that can be transmitted through the atmosphere.  (^) Because of ozone, water, carbon dioxide, and other molecules in the atmosphere, this saves us from harmful radiation. As a result, we only see specific portions of the electromagnetic (EM) spectrum. This phenomenon is known as the Earth’s “atmospheric window”. In remote sensing, sensors are built to pick up those specific spectral bands.

Atmospheric Window

 Not all of the EM spectrum hits the Earth’s surface. Atmospheric absorption prevents specific types of EM radiation to pass through the atmosphere.  The upper atmosphere blocks 100% of the gamma rays, x-rays, and most ultra-violet light. But visible light freely passes. Our eyes use this visible light to see features on Earth

Atmospheric Window

Band in micro meter Region 0.3-0.9 visible 1.0-1.1 Near/ Reflected IR 1.2-1.3 Near/ Reflected IR 1.5-1.8 Near/ Reflected IR 2.0-2.4 Near/ Reflected IR 3.5-4.0 Thermal IR 4.6-4.9 Thermal IR 8.0-13.0 Thermal IR Band (GHz) Region 0.3-0.9 Microwave 1.0-1.1 Microwave 1.2-1.3 Microwave 1.5-1.8 Microwave 2.0-2.4 Microwave 3.5-4.0 Microwave

Summery

 The atmospheric window applies to wavelengths of light at which electromagnetic radiation from the sun will penetrate the Earth’s atmosphere.  Remote sensing not only takes advantage of the visible spectrum (red, green, and blue) but also non-visible light.  This is why engineers keep in mind the atmospheric windows in the design process.

Reference

 Wikipedia.org  Jensen; Remote sensing of the Environment.  Thomas M. Lillesand, Ralph W. Kiefer, Jonathan W. Chipman; REMOTE SENSING AND IMAGE INTERPRETATION  Gisgeography.com/atmospheric windows.