Lecture 3
Download
1 / 57

Our atmosphere - PowerPoint PPT Presentation


  • 194 Views
  • Uploaded on

Lecture 3 Remote Sensing in the Visible and Reflected IR Region of the EM spectrum - The Effects of the Atmosphere on EM Radiation February 9th 2009.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Our atmosphere' - anais


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Lecture 3 Remote Sensing in the Visible and Reflected IR Region of the EM spectrum - The Effects of the Atmosphereon EM RadiationFebruary 9th 2009


SyllabusLecture/Hourly Exam Schedule and Assigned Readings (Subject to Change) Week Date Lecture Topic Reading Part I Remote Sensing Basics 1 26-Jan 1 Introduction to Remote Sensing Ch 1 28-Jan University Closed2 02-Feb 2 Principles of EM radiometry and basic EM Theory Ch 2 04-Feb Principles of EM radiometry and basic EM Theory II3 09-Feb3 Atmospheric Influences on EM Radiation 11-Feb 4 Photographic Systems/Image InterpretationCh 3,54 16-Feb 5 The Digital Image I Ch 4,10 18-Feb The Digital Image II5 23-Feb 6 Applications with areal and space photography 25-Feb Exam 1 26-Feb Lab 1 Introduction to ENVI – manipulation of digital imagery



Key components of vis rir remote sensing
Key components of VIS/RIR remote sensing

2. Energy emitted from sun based on Stephan/Boltzman Law, Planck’s formula, and Wein Displacement Law (Lecture 2)

1. Sun is EM Energy Source

VIS/NIR Satellite

EM energy

EM energy

3. EM Energy interacts with the atmosphere

5. EM Energy interacts with the atmosphere

Lecture 3

4.EM energy reflected from Earth’s Surface – Lectures 7/8


Lecture 3 topics key points
Lecture 3 Topics/Key Points

  • Key Atmospheric Constituents

    • Gases, water, particulate matter

  • Effects of the atmosphere on EM energy

    • Reflection, Absorption, Scattering, Transmittance

  • Atmospheric extinction and the attenuation coefficient

  • Net effects of the atmosphere on VIS/IR energy reaching the earth’s surface - atmospheric windows


What do gases and particles in the atmosphere do to em radiation
What do gases and particles in the atmosphere do to EM radiation?

  • Refraction

  • Reflection

  • Absorption

  • Scattering

  • Transmittance


90 km radiation?


Key components of vis nir remote sensing
Key components of VIS/NIR remote sensing radiation?

VIS/NIR Satellite

EM energy

EM energy

  • Constituents of the atmosphere that will interact with EM radiation

  • Gases – CO2, N2Ox, CH4, O2, O3

  • Water –

    • Water vapor

    • Water droplets

    • Ice particles

  • Particulate matter – smoke, dust, other particles


Atmospheric gases
Atmospheric Gases radiation?

Nitrogen – N2 – 78%

Oxygen – O2 – 21%

Argon – Ar – 1%

H20 – 0 to 7%

  • Major atmospheric trace gases (less than 0.1% each)

    Carbon dioxide – CO2

    Ozone – O3

    Methane – CH4

    Carbon Monoxide – CO

    Nitrous Oxide – N2Ox

    Chlorofluorocarbons (CFCs)


Water in the atmosphere
Water in the atmosphere radiation?

  • Water is present in a variety of forms in the atmosphere

    • Gas/vapor, droplets (liquid and frozen), ice crystals

  • The physical state (e.g., gas, liquid, solid) and density of water determines the manner in which it reacts with EM radiation

  • The amount of water in the atmosphere is highly variable, depending on climatic processes and earth/atmosphere interactions, particularly the hydrologic cycle


Impacts of atmospheric water
Impacts of atmospheric water radiation?

  • When water is present in the form of clouds, it totally blocks radiation in the visible/RIR region of the EM spectrum

  • In other forms, atmospheric water affects the absorption, scattering, and transmission of visible/RIR radiation through the atmosphere


Water is continuously being added to and removed from the atmosphere in a variety of forms through the global water cycle

This water strongly influences EM radiation is passing through the atmosphere – it is a very transient characteristic, e.g., it is always changing


Particulate matter
Particulate Matter atmosphere in a variety of forms through the global water cycle

  • Inorganic and organic particles that have been suspended in the atmosphere from a variety of sources


Sources of particulate matter
Sources of particulate matter atmosphere in a variety of forms through the global water cycle

Natural processes

  • Volcanic eruptions – ash and inorganic compounds (example - sulfur dioxide)

  • Dust storms – small soil particles (sand, silt, and clay)

  • Wildland fires – soot and ash

  • Biological processes – emissions of complex hydrocarbons

  • Sea mist – water in droplets blowing of the sea surface evaporates, leaving sea salts

    Human activities

  • Burning of fossil fuels – soot and inorganic compounds

  • Biomass burning – soot, ash


Dust cloud south of Iceland Observed by MODIS atmosphere in a variety of forms through the global water cycle


Smoke plume over atmosphere in a variety of forms through the global water cycle

Eastern US observed by MODIS in July 2002 from Forest Fires (red dots) in Quebec


Landsat Image of Mt. Pinatubo Eruption atmosphere in a variety of forms through the global water cycle


Temporal spatial variability of atmospheric constituents
Temporal/spatial variability of atmospheric constituents atmosphere in a variety of forms through the global water cycle

  • Particulate matter

    • Highly variable both spatially and temporally, driven by the hydrologic cycle

    • A regional phenomenon, dependent on sources

    • Corrections must be made to account for the impacts of particulate matter

    • Need to understand possible sources for particulate matter in the regions of interest


Temporal spatial variability of atmospheric constituents1
Temporal/spatial variability of atmospheric constituents atmosphere in a variety of forms through the global water cycle

  • Atmospheric water

    • Highly variable both spatially and temporally, driven by the hydrologic cycle

    • A global phenomenon

    • Corrections must be made to account for the impacts of atmospheric water

    • Need to understand how hydrologic cycle is influencing atmospheric water in the regions of study


Temporal spatial variability of atmospheric constituents2
Temporal/spatial variability of atmospheric constituents atmosphere in a variety of forms through the global water cycle

Trace gases CO2 CO N2Ox CH4CFC’s

  • Generally well mixed throughout the atmosphere

  • Change in response to physical, biological and chemical processes

  • Except for CO2, Spatial/temporal variations do not influence radiation in the VIS/RIR region of the EM spectrum


The bottom line
The bottom line!!! atmosphere in a variety of forms through the global water cycle

  • The constituents of the atmosphere are highly variable both spatially and temporally

  • These constituents interact with EM energy

  • To perform quantitative analyses of satellite remote sensing imagery requires an understanding of and accounting for atmospheric effects

  • Sophisticated computer models have been developed to quantify the effects of the atmosphere and to normalize remote sensing data for its effects


Lecture 3 topics key points1
Lecture 3 Topics/Key Points atmosphere in a variety of forms through the global water cycle

  • Key Atmospheric Constituents

    • Gases, water, particulate matter

  • Effects of the atmosphere on EM energy

    • Reflection, Absorption, Scattering, Transmittance

  • Atmospheric extinction and the attenuation coefficient

  • Net effects of the atmosphere on VIS/IR energy reaching the earth’s surface - atmospheric windows


Basic em energy matter interactions
Basic EM energy/matter interactions atmosphere in a variety of forms through the global water cycle

Incident EM Radiation

Reflection

Scattering

Refraction

Absorption

Transmittance


What do gases and particles in the atmosphere do to em radiation1
What do gases and particles in the atmosphere do to EM radiation?

  • Reflection

  • Absorption

  • Scattering

  • Transmittance


Reflectance the process whereby incoming em radiation is reflected off the surface of an object
Reflectance radiation?– the process whereby incoming EM radiation is reflected off the surface of an object

Incoming

Radiation

Outgoing

Radiation


Atmospheric reflection
Atmospheric Reflection radiation?

  • Reflection of EM energy in the Visible/RIR region of the EM spectrum occurs primarily from the tops of dense clouds

  • ~25% of incoming solar EM energy in this wavelength region is reflected by clouds

  • When clouds of particulate matter (e.g., smoke, dust, etc.) are particularly thick or dense, the reflection from the tops of these can also occur


Absorption
Absorption radiation?

  • The process by which EM radiant energy is absorbed by a molecule or particle and converted to another form of energy


UV radiation radiation?


Summary of atmospheric absorption
Summary of atmospheric absorption radiation?

  • Some trace atmospheric gases are strong absorbers of EM energy, but this absorption is confined to specific wavelength regions

  • Water is a very strong absorber of EM energy in specific wavelength regions > 0.7 m

  • Atmospheric particles will absorb some EM energy – because they are large, they tend to absorb all wavelengths equally


Scattering
Scattering radiation?

  • The process whereby EM radiation is absorbed and immediately re-emitted by a particleor molecule – energy can be emitted in multiple-directions

Incoming EM energy

Scattered energy

Note: No EM energy is lost during scattering


Types of scattering
Types of Scattering radiation?

  • Rayleigh scattering

  • Mie scattering

  • Non-selective scattering

    The type of scattering is controlled by the size of the wavelength relative to the size of the particle


Rayleigh scattering also called molecular scattering
Rayleigh Scattering radiation?(also called molecular scattering)

Occurs when the wavelength λ>> the particle size


Rayleigh scattering ~ 1 / radiation?4

Rayleigh scattering occurs at a molecular level

Through Rayleigh scattering, blue light (0.4 um) is scattered 5 times as much as red light (0.6 um)


90 km radiation?

Most Rayleigh scattering occurs in the top 10 km of the stratosphere, e.g., at the ozone layer


The clear sky appears blue because Rayleigh scattering high in the atmosphere influence short wavelength (blue) radiation the most

Note UV radiation is not scattered by the upper atmosphere because it is absorbed by the OZONE Layer

For further discussion of this slide, see

http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html#c5


Summary of rayleigh scattering
Summary of Rayleigh Scattering in the atmosphere influence short wavelength (blue) radiation the most

  • Occurs at the molecular level

  • The degree of Rayleigh scattering is inversely proportional to the fourth power of the EM wavelength

  • Most Rayleigh scattering occurs in the upper 10 km of the stratosphere


Mie scattering
Mie Scattering in the atmosphere influence short wavelength (blue) radiation the most

Occurs when the wavelength  particle size


Mie scattering1
Mie Scattering in the atmosphere influence short wavelength (blue) radiation the most

  • Occurs with particles that are actually 0.1 to 10 times the size of the wavelength

  • Primary Mie scatterers are dust particles, soot from smoke

  • Mie scatterers are found lower in the Troposphere


Where does Mie Scattering Occur? in the atmosphere influence short wavelength (blue) radiation the most

The sources of Mie scatterers are at the earth’s surface, therefore, Mie scatterers are largely confined to the lower troposphere

The exception are volcanoes, whose plumes of particulate matter are lifted well above the tropopause into the lower stratosphere


Non selective scattering
Non-Selective Scattering in the atmosphere influence short wavelength (blue) radiation the most

Occurs when the wavelength << particle size


Non selective scattering1
Non-Selective Scattering in the atmosphere influence short wavelength (blue) radiation the most

  • Its name derives from the fact that all wavelengths (visible/near IR) are equally affected

  • Particles are very large, typically water droplets and ice crystals of fog banks and clouds

  • Particles are 10 times the size of the wavelength, e.g., > 20 um in size


For further discussion of this slide, see in the atmosphere influence short wavelength (blue) radiation the most

http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html#c5


What do gases and particles in the atmosphere do to em radiation2
What do gases and particles in the atmosphere do to EM radiation?

  • Refraction

  • Reflection

  • Absorption

  • Scattering

  • Transmittance


sun radiation?

Reflected

Refracted

Scattered

Absorbed

Transmitted


Atmospheric transmittance
Atmospheric Transmittance radiation?

  • The fraction or percent of a particular frequency or wavelength of electromagnetic radiation that passes through the atmosphere without being reflected, absorbed or scattered.


Lecture 3 topics key points2
Lecture 3 Topics/Key Points radiation?

  • Key Atmospheric Constituents

    • Gases, water, particulate matter

  • Effects of the atmosphere on EM energy

    • Reflection, Absorption, Scattering, Transmittance

  • Atmospheric extinction and the attenuation coefficient

  • Net effects of the atmosphere on VIS/IR energy reaching the earth’s surface - atmospheric windows


Atmospheric extinction
Atmospheric Extinction radiation?

  • Extinction is a term used to account for the loss or attenuation of radiant energy as light passes through the atmosphere, and includes both scattering and absorption

  • Extinction quantifies the amount of atmospheric transmittance


Atmospheric extinction1
Atmospheric Extinction radiation?

Io - the unattenuated light intensity passing into the atmosphere

L - the path length through

the atmosphere

I - attenuated light intensity


Extinction coefficient
Extinction Coefficient - radiation?

I / Io= e- L

where

I is the attenuated light intensity

Io is the unattenuated light intensity

L is the path length through the a uniform medium such as the atmosphere

 is the extinction coefficient in the units of inverse distance


Extinction coefficient1
Extinction Coefficient - radiation?

 = bm + bp + k  

where

bmis the Rayleigh or molecular scattering coefficient

bpis the Mie scattering coefficient (due to the airborne particles)

k is the absorption coefficient


Lecture 3 topics key points3
Lecture 3 Topics/Key Points radiation?

  • Key Atmospheric Constituents

    • Gases, water, particulate matter

  • Effects of the atmosphere on EM energy

    • Reflection, Absorption, Scattering, Transmittance

  • Atmospheric extinction and the attenuation coefficient

  • Net effects of the atmosphere on VIS/IR energy reaching the earth’s surface - atmospheric windows


Atmospheric window
Atmospheric Window radiation?

  • Those regions of the EM spectrum which are to some degree unaffected by attenuation by constituents of the atmosphere, and therefore can be used in vis/RIR instruments for remote sensing of the earth’s surface


Visible radiation?

1 window

Near IR

3 windows

Shortwave IR

2 windows


Our atmosphere radiation?


Syllabus radiation?Lecture/Hourly Exam Schedule and Assigned Readings (Subject to Change) Week Date Lecture Topic Reading Part I Remote Sensing Basics 1 26-Jan 1 Introduction to Remote Sensing Ch 1 28-Jan University Closed2 02-Feb 2 Principles of EM radiometry and basic EM Theory Ch 2 04-Feb Principles of EM radiometry and basic EM Theory II3 09-Feb3 Atmospheric Influences on EM Radiation 11-Feb 4 Photographic Systems/Image InterpretationCh 3,54 16-Feb 5 The Digital Image I Ch 4,10 18-Feb The Digital Image II5 23-Feb 6 Applications with areal and space photography 25-Feb Exam 1 26-Feb Lab 1 Introduction to ENVI – manipulation of digital imagery


ad