TRAINEE GUIDE
Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
CIN-S-0618
28APR15
TRAINEE GUIDE FOR
ADVANCED FORECASTER COURSE
S-420-0618
UNIT 3, TOPIC 1 – ENVIRONMENTAL SATELLITE FUNDAMENTALS
PREPARED BY
THE COMET PROGRAM, UNIVERSITY CORPORATION FOR ATMOSPHERIC RESEARCH,
3085 CENTER GREEN DRIVE, BOULDER, CO 80301
PREPARED FOR
COMMANDER, NAVAL METEOROLOGY AND OCEANOGRAPHY COMMAND
1100 BALCH BLVD, STENNIS SPACE CENTER, MS 39529
APRIL 2015
Satellites – Unit 3.1
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TRAINEE GUIDE
Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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TABLE OF CONTENTS
CHANGE RECORD ....................................................................................................... ii
TABLE OF CONTENTS................................................................................................ iii
TERMINAL OBJECTIVES ........................................................................................ xiv
CHANGE RECORD
Description of Change
Entered By
Date
TABLE OF CONTENTS
1 Introduction
2 The Earth's Source of Energy Is the Sun.
3 The Earth’s Atmosphere and Oceans Redistribute This Incoming Solar Energy.
4 The Earth’s Heat Fluxes.
5 What Happens to This Energy?
6 How Does This Relate to Remote Sensing?
7 Applications of the Electromagnetic Spectrum and Observed Frequencies.
8 What Is Being Observed By Satellite Frequencies?
9 Summary
10 Answers to Checkpoint Questions
11 List of Figures
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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UNIT 3: ADVANCED REMOTE SENSING CAPABILITIES
Terminal Objective 3.0: Analyze satellite imagery for atmospheric inducements.
TOPIC 3.1 environmental satellite fundamentals
1 - INTRODUCTION
In this lesson we are addressing the following enabling objectives:

EO 3.1.1: DESCRIBE the fundamental concepts of Environmental Satellite Remote
Sensing without reference with 75% accuracy.

EO 3.1.2: EXPLAIN how the Electromagnetic Spectrum effects observed frequencies
without reference with 75% accuracy
The following remote sensing principles will be reviewed:
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The energy of the sun
How the earth redistributes this incoming energy
An overview of radiation
How environmental satellites rely on radiation
The observation of electromagnetic signals
What satellites are observing with these signals.
2 - THE EARTH’S SOURCE OF ENERGY IS THE SUN
The sun is fueled by nuclear energy – fusion in the formation of helium (He) from hydrogen
(H). This energy passes through space as radiation (light - packets of energy / photons).
ENERGY is defined as a property that enables something to do WORK
WORK is a measure of the change a FORCE produces, for example
W = Force * distance (mechanical definition)
The units of both W and E is the Joule (J)
Energy is found in many forms.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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Fig. 0618-01-01. Table of energy forms.
The Principle of Conservation of Energy: Energy can be converted back and forth between
forms but is never lost.
3 - THE EARTH’S ATMOSPHERE AND OCEANS REDISTRIBUTE THIS INCOMING SLOAR
ENERGY
Insolation is defined as incoming solar energy (sunlight). It is mostly visible light (VL,
49%) but also ultra-violet (UV, 9%) and infrared (IR, 42%)
The Electromagnetic Spectrum is the distribution of energy by wavelength as shown.
Fig. 0618-01-02. The electromagnetic spectrum with the Visible Light (VL) range indicated.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
CIN-S-0618
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Fig. 0618-01-03. The coloring indicates the difference between incident solar energy
density (watts/m2) at the equator and poles.
The Earth intercepts sunlight, and the sun’s rays are almost parallel as they reach the earth.
The result is an uneven distribution of insolation and thus, temperature on the earth's
surface. There is an excess of solar energy received in the equatorial regions and a deficit
at the poles. The earth’s declination relative to the sun adds to the polar deficit when
regions north (south) of the Arctic (Antarctic) Circle receive no solar energy during their
polar winters. The earth’s atmosphere and ocean redistribute this incoming energy.
Eventually, the earth re-radiates this energy back to space in the infrared band.
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TRAINEE GUIDE
Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
CIN-S-0618
28APR15
Fig. 0618-01-04. Illustration of excess incoming radiation in the equatorial regions, deficit
at the poles, and resultant poleward transport by the oceans and atmosphere.
CHECK QUESTION 1: The tropics are an area of net energy (radiation) _____ compared to all
latitudes on Earth.
a.
b.
c.
d.
gain
loss
equilibrium
none of the above; the tropics do not receive or emit any radiation.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
CIN-S-0618
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4 - THE EARTH’S HEAT FLUXES
Fig. 0618-01-05. Schematic of the earth’s heat fluxes.
If the net sum of these Q’s in Fig. 0618-01-05 is zero, there is no temperature change and
the system is in energy balance (meaning there is no global warming). Radiation Fluxes
are incoming Qs (VL, visible light) and outgoing Qb (IR, infrared)
Why is the sun radiating in visible light while earth radiates in IR? It is a matter of their
temperatures. The Stephan-Boltzmann Law relates energy released to the body's "Black
Body" temperature by the fourth power of the temperature in °K (°C + 273.15). Qb = σ T4,
where Qb is the energy release rate (flux) in calories/cm2/s, and the Stephan-Boltzmann
Constant is  = 1.36 x 10-12 calories/(cm2 s °K4).
Examples:
SUN T = 6000°K (~5700°C), so
Qb-sun = 1300 cal/cm2/s
EARTH T = 288°K (~15°C or 59°F)
Qb-earth = 0.0094 cal/cm2/s (1/250,000 less than sun)
EARTH T = 255°K (~-18°C or 0°F) without the atmosphere
Qb-earth = 0.0057 cal/cm2/s
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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Fig. 0618-01-06 and Fig 0618-01-07. (left) Radiance spectral energy curves for solar
(yellow) and earth (red) black bodies. (right) The same curves annotated with the
wavelengths of peak emission for shortwave or visible solar (Vis), longwave infrared earth
(LWIR), and overlapping wavelengths (NearIR and SWIR).
WIEN'S LAW relates the wavelength of the maximum energy released by a radiating body
to its temperature: λmax = C3 / T, where C3 = 2892 micrometer °K, 1 micrometer = 10-6 m.
Examples:
SUN: λmax = 0.54 µm (visible light, centered on BLUE)
EARTH: λmax = 10 µm (far IR)
CHECK QUESTION 2: The sun’s emits radiation primarily in the _____ portion of the EM
spectrum and at relatively _____ temperature, according to Wien’s Law.
In this course, we often use frequency, the inverse of wavelength. That is:
f = 2 π/ λ (in cycles/second or Hertz)
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5 - WHAT HAPPENS TO THIS ENERGY?
Fig. 0618-01-08. Energy budget for the earth.
341 Wm-2 (100%) of the incoming solar energy or insolation reaches the top of the
atmosphere (Fig. 0618-01-08).





Some of this insolation is reflected by clouds and the ocean surface, reradiating
about 30% directly back into space.
About 23% is absorbed by the atmosphere and 47% by the earth’s surface (land and
sea).
The earth surface emits infrared energy that is 116% of the incoming insolation.
94% of this energy is reflected back by clouds or absorbed and reradiated in an
energy cycle within the lower atmosphere. This is the Greenhouse Effect: the
atmospheric blanket that keeps the earth system at a livable temperature.
10% of the surface’s infrared radiation passes through the atmosphere, joins the
infrared energy that is radiated upward by clouds and clear air, and departs the
earth system.
In summary, 30% of the incoming solar radiation is reflected and 70% is converted
to infrared energy and eventually re-radiated into space.
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CHECK QUESTION 3: What happens if more energy from the sun’s visible light enters the
earth system than departs as infrared radiation?
6 - HOW DOES THIS RELATE TO SATELLITE REMOTE SENSING?
Fig. 0618-01-09. Radiation absorption curves for various atmosphere constituents.
In Figure 0618-01-09, the yellow shading shows the incident sunlight at the top of the
atmosphere. The red shading shows how much of this energy reaches the Earth’s surface.
Regions where the yellow is thin or missing are “radiation windows” that are letting the
sun’s energy through. Regions where the yellow extends downward show bands where the
energy is absorbed through reactions with the indicated chemicals.
Examples shown are:




O3 at the short UV wavelength of 250 nm
O2 in the IR wavelength of 750 nm
H2O in 5 different regions
CO2 in the far IR at about 2050 nm.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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Fig. 0618-01-10. Radiation absorption and transmission windows.
Fig. 0618-01-10 shows the transmittance, or percentages of energy that passes through the
atmosphere. Note that compared with the above plot, there are a number of chemicals in
addition to H2O and CO2 that absorb radiation.
Fig. 0618-01-11. An illustration of the total electromagnetic spectrum, from X-Rays to
electricity. The thermal radiation region matches the solar and earth radiation regions
noted earlier.
Satellite remote sensing applications are possible because of the ways in which the
atmosphere and other earth systems interact with the entire electromagnetic spectrum
(Fig. 0618-01-11). The portions of the electromagnetic spectrum where there is little
atmospheric absorption are referred to as "windows" and are used to observe surface
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
CIN-S-0618
28APR15
properties. The atmosphere is most transparent in the visible and the microwave parts of
the spectrum and opaque in the infrared, except for a small window close to 10 μm.
Satellite sensors measure energy at particular wavelengths, which are referred to as
"channels" and numbered in increasing order from shortwave to longwave. The visible,
infrared, and microwave wavelengths are used most often in environmental remote
sensing.
CHECK QUESTION 4: List 3 of the main atmospheric absorption bands, including the
approximate wavelength and atmospheric constituent primarily responsible.
1. _______________________________________________________________________________________
2. _______________________________________________________________________________________
3. _______________________________________________________________________________________
7 - APPLICATIONS OF THE ELECTROMAGNETIC SPECTRUM AND OBSERVED
FREQUENCIES
Abbreviations for various instrument frequency bands include:
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

VIS (visible)
IR (infrared)
NIR (near infrared)
SWIR (shortwave infrared)
MWIR (medium wavelength infrared)
TIR (total or thermal infrared radiation)
MW (microwave)
UV (ultraviolet).
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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Fig. 0618-01-12. Examples of windows and regions that are opaque to microwaves in the
electromagnetic spectrum.
Throughout this unit, the operating frequencies of satellite instruments are listed. There
are multiple approaches and objectives for the selected frequencies:
See through the atmosphere and collect information about the surface. These channels
are located in window regions where there is little absorption by atmospheric gases.
 At times, corrections must be made, as these windows are not totally transparent.
 They help identify properties associated with earth and ocean surfaces as well as
clouds.
 Visible vegetation and smoke, wave data from radar, and infrared radiation
observations of sea surface temperature are examples.
Reflect off atmospheric components and thus collect information about their presence,
elevation, concentration, etc.
 Examples are the observations of water vapor in clouds or ozone levels.
Are reradiated by the atmosphere, surface, or components.
 These channels, located in absorption regions, are sensitive to a range of
atmospheric gases like water vapor, carbon dioxide, and oxygen.
 Clouds that reflect, absorb, and reradiate at different frequencies are an example.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
CIN-S-0618
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Channels in both window and absorption regions can be used to derive a variety of
products including cloud properties.
Fig. 0618-01-13. An example of the electromagnetic spectrum and the frequencies
observed by the VIIRS instrument suite.
Figure 0618-01-13 shows the many channels that the JPSS VIIRS system observes. Note
that they range from visible light to longwave infrared. This will be discussed later in the
JPSS section of Unit 3.2.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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Fig. 0618-01-14. Japanese Advanced Himawari Imager (AHI) sensor channels.
Figure 0618-01-14 is a table of the 16 wavelength channels observed by the Japanese
Advanced Himawari Imager (AHI). The right column indicates how each channel is use.
This will be discussed later in the Himawari section of Unit 3.2.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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Fig. 0618-01-15. Images illustrate the 16 channels of the AHI. When used singly or in
combination, various channels can be used to observe certain phenomena.
For example, the frequency channels on the recently deployed Japanese Himawari
geostationary satellite were selected to observe certain phenomena (Fig. 0618-01-15).
(a)
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(b)
(c)
(d)
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(e)
(f)
(g)
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(h)
(i)
(j)
Fig. 0618-01-16. Applications of data from the GOES-R Advanced Baseline Imager (ABI):
(a)air quality, (b) climate, (c) cloud properties, (d) convection, (e) wildfires, (f)
precipitation, (g) surface properties, (h) storms, (i) atmospheric temperature and moisture,
and (j) winds.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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Similarly, GOES-R data are being used to observe or derive a variety of atmospheric
properties and components. Many of these products will be discussed further in Unit 3.3.
CHECK QUESTION 5: Describe 3 approaches/objectives to the operating frequencies of
satellite instruments, and give an example of a common product for each.
1. _______________________________________________________________________________________
2. _______________________________________________________________________________________
3. _______________________________________________________________________________________
8 - WHAT IS BEING OBSERVED BY SATELLITE REMOTE SENSING?
Observed phenomena and properties include the following:
Electromagnetic radiation:
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
Visible light
Infrared
Ultraviolet
Microwave.
Atmospheric properties:
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Temperature
Water content
Water vapor
Clouds
Winds
Lightning.
Particulates in the atmosphere:
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
Snow / ice
Aerosols
Dust
Volcanic ash
Salt spray.
Atmospheric chemistry:
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Ozone
Carbon monoxide / dioxide
Greenhouse (methane, etc.).
Oceanographic properties
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Temperature
Salinity
Altimetry (surface elevation)
Color
Waves
Currents
Bioluminescence.
Solar Properties
 Solar winds
 Solar events (flares, etc.).
The satellites, systems, and instruments that collect the data required to create these
products will be presented in the next section, Topic 3.2. The environmental properties
will be presented in terms of observed and derived meteorological and oceanographic
products in the section that follows, Topic 3.3. How Numerical Weather and
Oceanographic Prediction (NWP and NOP) assimilate this information will be discussed in
the final section, Topic 3.4.
9 - SUMMARY
We have briefly presented the basics of radiation energy and demonstrate how the
measurements of radiation at various frequencies or wavelengths are used by
environmental satellites.
In particular, this topic has covered:
 The sun as the earth system’s energy source
 The earth’s redistribution of incoming energy
 A quick overview of radiation principles
 The reliance of environmental satellite systems on radiation
 What these satellites are observing.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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10 - CHECK QUESTION ANSWERS
CHECK QUESTION 1: The tropics are an area of net energy (radiation) _____ compared to all
latitudes on Earth.
a.
b.
c.
d.
gain
loss
equilibrium
none of the above; the tropics do not receive or emit any radiation
ANSWER: a. gain
CHECK QUESTION 2: The sun’s emits radiation primarily in the _____ portion of the EM
spectrum and at relatively _____ temperature, according to Wien’s Law.
a. visible, high
b. infrared, low
c. ultraviolet, very high
ANSWER: a. visible, high
CHECK QUESTION 3: What happens if more energy from the sun’s visible light enters the
earth system than departs as infrared radiation?
ANSWER: The earth system will heat up.
CHECK QUESTION 4: List 3 of the main atmospheric absorption bands, including the
approximate wavelength and atmospheric constituent primarily responsible.
POSSIBLE ANSWERS include any wavelengths listed for the following:
● O3 at the short UV wavelength of 250 nm (0.25 µm) and at
approximately 10 µm
● O2 in the IR at 750 nm (0.75 µm) and at approximately 0.25 cm and
0.50 cm
● H2O in 5 regions, concentrated near: 1.4 µm, 1.8 µm, 2.7 µm, 6-7 µm
and from about 20 - 100 µm
● CO2 at 2050 nm (2.05 µm), at 4.5 µm, and at 15 µm
● CH4 at approximately 3.5 µm and 8 µm
CHECK QUESTION 5: Describe 3 approaches/objectives to the operating frequencies of
satellite instruments, and give an example of a common product for each.
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Advanced Forecasters – Satellites, Unit 3, Topic 1 - Fundamentals
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ANSWERS:
1. “Seeing through the atmosphere” - channels are located within window regions so
that surface information can be sensed. Example: vegetation index, sea surface
temperature
2. “Reflection/scattering from atmospheric components” - channels are located within
wavelengths for which certain constituents scatter or reflect most incident solar
radiation. Example: concentration of water vapor in clouds, concentration of ozone
3. “Reradiated or absorbed by surface or atmospheric components” – channels are
located within absorption bands. Example: water vapor imagery, CO2
concentration, etc.
11 - LIST OF FIGURES
Fig. 0618-01-01. Table of energy forms.
Fig. 0618-01-02. The electromagnetic spectrum with the Visible Light (VL) range indicated.
Fig. 0618-01-03. The coloring indicates the difference between incident solar energy
density (watts/m2) at the equator and poles.
Fig. 0618-01-04. Illustration of excess incoming radiation in the equatorial regions, deficit
at the poles, and resultant poleward transport by the oceans and atmosphere.
Fig. 0618-01-05. Schematic of the earth’s heat fluxes.
Fig. 0618-01-06. Radiance spectral energy curves for solar (yellow) and earth (red) black
bodies.
Fig. 0618-01-07. The same curves annotated as in 01-06, with the wavelengths of peak
emission for shortwave or visible solar (Vis), longwave infrared earth (LWIR), and
overlapping wavelengths (NearIR and SWIR).
Fig. 0618-01-08. Energy budget for the earth.
Fig. 0618-01-09. Radiation absorption curves for various Earth processes.
Fig. 0618-01-10. Radiation absorption and transmission windows.
Fig. 0618-01-11. An illustration of the total electromagnetic spectrum, from X-Rays to
electricity. The thermal radiation region matches the solar and earth radiation regions
noted earlier.
Fig. 0618-01-12. Examples of windows and regions that are opaque to microwaves in the
electromagnetic spectrum.
Fig. 0618-01-13. An example of the electromagnetic spectrum and the frequencies
observed by the VIIRS instrument suite (discussed in the JPSS section).
Fig. 0618-01-14. A table illustrating the 16 channels observed by the Japanese Advanced
Himawari Imager (AHI)
Fig. 0618-01-15. Images to illustrate the 16 channels observed by the Japanese Advanced
Himawari Imager (AHI)
Fig. 0618-01-16. Applications of data from the GOES-R Advanced Baseline Imager (ABI):
(a)air quality, (b) climate, (c) cloud properties, (d) convection, (e) wildfires, (f)
precipitation, (g) surface properties, (h) storms, (i) atmospheric temperature and moisture,
and (j) winds.
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