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INTERACTION OF EM WITH ATMOSPHERE Course: Introduction to RS & DIP Mirza Muhammad Waqar Contact: +92-21-34650765-79 EXT:2257 RG610.

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Presentation on theme: "INTERACTION OF EM WITH ATMOSPHERE Course: Introduction to RS & DIP Mirza Muhammad Waqar Contact: +92-21-34650765-79 EXT:2257 RG610."— Presentation transcript:

1 INTERACTION OF EM WITH ATMOSPHERE Course: Introduction to RS & DIP Mirza Muhammad Waqar Contact: EXT:2257 RG610

2 Outlines  Remote Sensing System  The Energy Source  The Atmosphere  The Energy-Matter Interaction at the Earth’s Surface  The Sensor  The data processing and supply system  The multiple data users  An ideal Remote Sensing System

3 Remote Sensing System 3

4 Electromagnetic Radiations  c = f λ  c = 3x10 8 m/sec  Either f, λ can be used for characterization of EM radiations.

5 Electromagnetic Radiation  Remote sensing is based on detecting electromagnetic (EM) energy.  Since the speed of light is constant, wavelength and frequency are inversely related to each other.

6 Electromagnetic Radiation 6

7 Black Body Radiations

8 Energy Interactions in the Atmosphere 8  Irrespective of its source, all radiations detected by remote sensors passes through some distance of atmosphere  The path length can vary widely depending upon  Source of illumination elevation angle  Sensor view angle  Following phenomena can take place, while interaction of energy in atmosphere.  Scattering  Absorption

9 Scattering  Scattering occurs when particles or large gas molecules present in the atmosphere interact with and cause the electromagnetic radiation to be redirected from its original path.  Type of Scattering  Raleight Scattering  Mie Scattering  Non Selective Scattering

10 Rayleigh Scatter  Rayleigh scatter is common when radiation interacts with atmospheric molecules and other tiny particles that are much smaller in diameter than the wavelength of interacting radiation.  The effect Rayleigh scatter is inversely proportional to the fourth power of wavelength.  Hence shorter wavelengths will scatter more by Rayleigh scatter.

11 The Blue Sky ~  A “blue” sky is a manifestation of Rayleigh scatter.  In the absence of scatter, the sky would appear black.  Sunlight interacts with the earth’s atmosphere,  It scatter the shorter (blue) wavelength more dominantly than the other visible wavelengths.  Consequently, we see a blue sky.

12 Mie Scattering  Mie scattering occur when atmospheric particle diameters essentially equal the wavelengths of the energy being sensed.  Water vapors, dust particles are major causes of Mie scatter.  Mie scatter influence longer wavelengths as compared to the Rayleigh scatter.

13 Non-Selective Scattering  It occurs when the diameter of the particles causing scatter are much larger than the wavelengths of the energy being sensed.  Water droplets, for example causes such scatter.  This scattering is “nonselective” with respect to wavelength.  Hence in visible, equal quantities of blue, green and red light are scatter, hence fog and cloud appear white in satellite images.

14 Absorption  Atmospheric absorption results in the effective loss of energy.  The most efficient absorbers of solar radiation in atmosphere are  Water vapor  Carbon dioxide  Ozone  The wavelength range in which the atmosphere is particularly transmissive of energy are referred to as atmospheric windows.

15 Atmospheric Windows 15  The wavelength ranges in which the atmosphere is particularly transmissive of energy are referred to as atmospheric windows.

16 Questions & Discussion


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