EOG 1200 Module 1 SMU earth sun radiations systems

Description

Objectives The objectives of this lab are: To describe differences in seasonal variations at different latitudes on Earth.To explain differences in seasonal variations.

3 attachmentsSlide 1 of 3attachment_1attachment_1attachment_2attachment_2attachment_3attachment_3

Unformatted Attachment Preview

SAINT MARY’S UNIVERSITY
DEPARTMENT OF GEOGRAPHY
GEOG 1200
Module 1: EARTH-SUN RADIATION SYSTEM AND SEASONS
Objectives
The objectives of this lab are:
1.
To describe differences in seasonal variations at different latitudes on Earth.
2.
To explain differences in seasonal variations.
Section 1: Key Terms
The following key terms are relevant to this lab.
•
Equator
•
Subsolar point
•
Axial tilt
•
North Pole
•
Solar declination
•
Circle of illumination
•
South Pole
•
•
Revolution
•
Arctic Circle
Summer Solstice
(June 21)
Rotation
Antarctic Circle
•
•
•
Winter Solstice (Dec. 21)
•
Tropic of Cancer
•
•
Tropic of Capricorn
Spring (or Vernal)
Equinox (March 21)
•
Autumnal Equinox
(Sept. 22)
Note: Dates for solstices and
equinoxes are for the Northern
Hemisphere. For the Southern
Hemisphere the seasonal labels
are reversed.
Before moving ahead, ensure your understanding of these terms. Most found in Chapter of your textbook.
Figure 1 shows the names and positions of the seven important lines of latitude on Earth:
Figure 1
Section 2: Describing Seasonal Variations on Earth
For this section the amount of insolation (incoming solar radiation), as measured at the top of the atmosphere (TOA), will
be used to represent the prime control of seasonal variations on Earth. Differences in seasonal variations at different
latitudes on Earth will be described by plotting graphs of insolation over time, with the values to plot to be obtained by
reading directly off Figure 2 (next page).
1
Values for the North Pole
(W m-2):
Figure 2
1.
J:
0
F:
0
M:
0
A:
240
M:
450
J:
530
J:
480
A:
290
S:
40
O:
0
N:
0
D:
0
(from Christopherson and Byrne, 2009, Figure 2.10)
At each of the latitudes a) – h) below, use Figure 2 above to obtain values of daily insolation (units: Watts per
square meter, or W m-2) for each month of the year. Read off the values at the middle of each month’s column,
and estimate intermediate values between the lines. For example, the value for January at 40°N would be ~180
W m-2. (If you read off the value for January at 40°N, do you get this answer? Try it now and make sure.)
Plot the values on the graphs provided (on a separate sheet) and connect the points with smoothed lines.
To help you get started, values for the North Pole are given (above right) and the points have been plotted on
the corresponding graph. Go through the North Pole values to confirm you understand how to read values from
the graph. Note that the June value must be greater than 500 W m-2 but less than 550 because there is no 550
line shown, so an intermediate value of 530 W m-2 was estimated.
a)
b)
c)
2.
North Pole
South Pole
Arctic Circle
d)
e)
Antarctic Circle
45°N, Halifax’s
latitude
f)
g)
h)
Tropic of Cancer
Equator
Tropic of Capricorn
Recall that the amount of insolation is being used to represent seasonal variations on Earth, because in simple
terms more insolation results in warmer temperatures. Use the completed graphs from Question 1 to summarize
seasonal variations by answering these questions:
a)
Describe how seasonal extremes of insolation (the difference between maximum and minimum values)
vary with latitude.
2
b)
How do the patterns of seasonal variation at latitudes in the northern hemisphere (e.g., the Tropic of
Cancer) compare with the patterns at the corresponding latitudes in the southern hemisphere (e.g., the
Tropic of Capricorn)?
Section 3: Explaining Seasonal Variations
The two key controls on the amount of insolation received at any latitude during the year are 1) the angle of incidence,
which determines over how much surface area incoming beams of insolation are spread, and 2) daylength.
Subsolar Point and Solar Declination
Due to the geometry of the Earth-Sun system, at any time of the year the Sun appears to be directly overhead one point
on Earth. That point is called the subsolar point. Beams of insolation arrive perpendicular to the surface only at the
latitude of the subsolar point. At all other latitudes, the beams of insolation arrive at an oblique angle. During the year,
the subsolar point migrates in a regular and predictable pattern to latitudes north and south of the Equator. The latitude
of the subsolar point at a given time is called the solar declination. Solar declination (which has units of degrees) is
shown with a dashed line on Figure 2.
[Note that for Questions 3 and 4, all of the answers are contained within the list a) – h) in Question 1.]
3.
What is the highest latitude in the northern hemisphere to which the subsolar point migrates annually? And the
highest latitude in the southern hemisphere?
4.
At the Spring (Vernal) Equinox (labeled on Figure 2), what is the latitude of the subsolar point? And at the
Autumnal Equinox, the Summer Solstice, and the Winter Solstice?
Intensity of Insolation
Because the Earth’s surface is curved, the intensity of insolation is not equal at all locations (recall Figure 2.9 in the
textbook). Only at the subsolar point is the intensity at its maximum. At all other locations, the more obliquely the
surface is oriented to the insolation, the lower the intensity of insolation. Using some simple trigonometry (Equation 1),
the intensity of insolation received at different places can be calculated. The answer from Equation 1 will be a
percentage of the intensity of insolation re-ceived on a flat surface that is perpendicular to the insolation. Answers will
be no smaller than 0 and no larger than 100.
Equation 1:
X = sin(90 – L) x 100
where: X = intensity of insolation (percent)
sin = the sine function
L = latitude (°), a positive value whether N or S
For Equation 1, first find the answer for (90 – L), then press the sin button, and then multiply that result x 100.
The sin function can be found on most calculators, but the calculator must be in degrees mode―not radians mode―for
Equation 1 to give correct results. Check your calculator now to see if you get these correct answers: sin(0) = 0,
sin(45) = 0.71, and sin(90) = 1.
5.
Complete Table 1. This table corresponds to the Spring and Autumn Equinoxes, when the solar declination is 0°.
After completing the column for the northern latitudes, ask yourself if there is a shortcut for completing the
column for the southern latitudes without doing any more calculations. (There is!)
The purpose of completing Table 1 is to show how the intensity of insolation varies with latitude.
Table 1: Proportions of Insolation at the Equinoxes
Latitude (°N)
X = sin (90 – L)
x 100
90
75
26
Latitude (°S)
X = sin (90 – L)
x 100
Latitude (°)
15
66.5°N
30
23.5°N
60
45
45
60
23.5°S
30
75
66.5°S
15
90
X = sin (90 – L)
x 100
0°
3
Note that the intensity of insolation is calculated here for the equinox dates when the solar declination is 0°. At other
times of the year, the latitude of maximum insolation intensity corresponds to the solar declination, and the intensity of
insolation at other latitudes corresponds proportionally.
Circles of Illumination
At any one time, only (and exactly) one half of the Earth is illuminated by the Sun; that is, the circle of illumination.
This is why we have periods of day and night, as the Earth rotates on its axis daily through the circle of illumination.
Because of the axial tilt (23½° from vertical), the range of latitudes receiving solar illumination varies during Earth’s
annual revolution around the Sun.
6.
Figure 3 shows the Earth in two dimensions at the Summer Solstice, with the Northern Hemisphere tilted towards
the Sun. On the diagram, lightly shade the half of the Earth that does not receive insolation. To determine the
correct half, draw a straight line between the highest point on the circle perimeter (the highest point is below
the vertical dashed line at the top of the circle, not at the North Pole, because the Earth is tilted) and the
lowest point on the circle perimeter. Then shade the side of Earth facing away from the insolation. Label the
unshaded portion of the diagram DAY, and the shaded portion NIGHT.
Figure 3
(Summer Solstice)
7.
Repeat the circle of illumination exercise for the Autumn Equinox (Figure 4), Winter Solstice (Figure 5), and
Spring Equinox (Figure 6).
4
Figure 4
(Autumnal Equinox)
Note that the Earth is still
tilted on its axis of rotation at
an angle of 23.5°. However, to
draw the diagrams for the
equinoxes on a flat sheet of
paper, the perspective (location
from which Earth is being
viewed) must be changed in
comparison to the solstices.
Figure 5
(Winter Solstice)
Figure 6
(Spring Equinox)
5
8.
As shown in Figure 2, there are some latitudes that do not receive any insolation during certain parts of the
year. In Figures 3-6, the range of latitudes that do receive insolation falls within the unshaded (DAY) part of the
diagram. Consult Figures 3-6 to fill in Table 2 by listing the most northerly and southerly latitudes that receive
insolation at the solstices and equinoxes. Give latitude values in degrees (°, including the hemisphere, N or S).
Table 2: Range of Latitudes Receiving Insolation
Date
Most Northerly Latitude
Most Southerly Latitude
Summer Solstice
Autumn Equinox
Winter Solstice
Spring Equinox
Daylength
In addition to the angular relationship between Earth surfaces and insolation, daylength is the other principal factor that
controls seasonal variations. Figures 3-6 can be used to estimate daylengths at different latitudes.
9.
Estimate daylengths for the Summer Solstice by using Figure 3 and these steps:
a)
Using a ruler with mm markings, measure the full length of each line listed in Table 3, in mm (except the
North and South Poles which will be addressed in part e below). Be precise with your measurements.
This length is A.
b)
Measure the length of part of the line that lies within the circle of illumination (the part labeled DAY).
This length is B.
c)
Calculate the proportion of the lengths of the two lines (shorter [B] divided by longer [A]), and express as
a decimal value. This result is C. In equation form: C = B/A.
d)
Multiply C x 24 (hours). The answer is the value D.
e)
For the North and South Poles, which are actually points not lines, it is not possible to measure line
length. However, you can examine Figure 3 and the other answers in the table below to figure out what
the daylengths are at the poles.
Table 3: Daylengths at the Summer Solstice
A
North Pole
C
D
Length of line
(mm)
B
Length of line within
circle of illumination
(mm)
C=B/A
(no units)
D = C x 24
(hours)
――――
――――
――――
63
31.5
0.5
――――
――――
――――
Arctic Circle
Tropic of Cancer
Equator
12
Tropic of Capricorn
Antarctic Circle
South Pole
If you have done everything correctly, you should find that for the Equator, line B is half the length of line A
and the final answer is 12 hours (A = 63 mm; B = 31.5 mm; C = B / A = 0.5; and D = 0.5 x 24 = 12 hours).
6
10. Repeat Question 9 for the Autumnal Equinox, using Figure 4 and Table 4.
Table 4: Daylengths at the Autumnal Equinox
A
North Pole
C
D
Length of line
(mm)
B
Length of line within
circle of illumination
(mm)
C=B/A
(no units)
D = C x 24
(hours)
――――
――――
――――
63
31.5
0.5
――――
――――
――――
Arctic Circle
Tropic of Cancer
Equator
12
Tropic of Capricorn
Antarctic Circle
South Pole
7
c) ______________________________
Graphs for Question 1
f) ______________________________
The order of the graphs a) – h) has been
chosen to enable summary and comparison in
Question 2.
600
Daily Insolation (W per sq. m)
Write the name of the line of latitude on
the blank line above each graph.
Daily Insolation (W per sq. m)
600
500
400
300
200
100
0
M
A
M
J
J
A
S
O
N
400
300
200
100
M
J
J
A
S
O
N
500
400
300
200
100
F
M
A
M
J
J
A
S
O
N
300
200
100
F
M
A
M
J
J
A
S
O
N
D
J
A
S
O
N
D
300
200
100
F
M
A
M
J
J
A
S
O
N
D
h) ______________________________
600
500
400
300
200
100
0
0
J
400
J
Daily Insolation (W per sq. m)
Daily Insolation (W per sq. m)
400
M
500
D
600
500
A
g) ______________________________
e) ______________________________
600
M
0
J
D
F
600
b) ______________________________
J
100
J
0
A
200
D
Daily Insolation (W per sq. m)
Daily Insolation (W per sq. m)
Daily Insolation (W per sq. m)
500
0
Daily Insolation (W per sq. m)
F
600
600
M
300
d) ______________________________
a) North Pole
F
400
0
J
J
500
500
400
300
200
100
0
J
F
M
A
M
J
J
A
S
O
N
D
J
F
M
A
M
J
J
A
S
O
N
D
Visualizing Physical Geography
by Timothy Foresman & Alan Strahler
Chapter 1
Discovering the Earth’s Dimensions
© Brenda Kean/Alamy
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Chapter Overview
The World of Geography
The Shape of the Earth
Global Location
Global Time
Mapping the Earth
Courtesy of NASA
Frontiers in Mapping Technologies
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
What is
happening in
this photo?
The World of Physical Geography
Physical geography plays a valuable role in:
• Understanding the planet
• Addressing issues of sustainability
• Population increase
• 6.9 billion today
• Estimated 10 billion
people in 40 years
• Integrating the human and
physical world
Courtesy of NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
The Science of Geography
• Geographers study Earth.
• Geographers consider:
• Spatial considerations (related to physical space)
• Temporal considerations (related to changes of time)
1973
2006
USGS, courtesy NASA/Goddard Space Flight Center
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
What are some of the spatial and temporal
changes between these two photos?
1973
2006
USGS, courtesy NASA/Goddard Space Flight Center
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
The five essential themes of geography:
• Location
• Home address
• GPS = Global Positioning System
• Place
• Region
• Human-Earth relationships
• Movement
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
The Science of Geography:
• Physical Geography
• Study of the Earth’s living and nonliving systems
• Study of landscapes, and natural processes such as
weather, climate, and geology
• Human Geography
• Study of spatial interactions and patterns related to
human activity such as social, cultural, and economic
topics
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
The Science of Geography:
• Technology, Tools, and Quantitative Methods
• Cartography
• GIS = Geographical Information Systems
• Remote Sensing
• Statistics
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
The World of Physical Geography
The World of Systems
• Constant Interactions of
energy and material between
the Earth’s four major
systems:
• Atmosphere
• Hydrosphere
• Lithosphere
• Biosphere
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
The World of Physical Geography
Methods and Tools for Geography
•Eratosthenes
• No shadow on summer solstice in Aswan
• Earth’s size
•Today’s technology
• Remote sensing
• GIS
• GPS
• Internet
• Web-based mapping tools
•Methods
• Scientific method
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Courtesy NASA
The World of Physical Geography
Methods and Tools for Geography
• Scientific method = the formal process that a scientist uses
to solve a problem, which involves first observing and
formulating a hypothesis and then testing and evaluating
results
Hypothesis = logical explanation for a process or
phenomenon that allows prediction and testing by
experiment
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Methods and Tools for Geography
• Steps of the Scientific Method
1. Generate critical inquiry from investigations and field
observation.
2. Formalize questions into a testable hypothesis to
explain observations.
3. Select method(s) of analysis and control for variables
and conditions for experiment.
4. Collect data for controlled experiment.
5. Conduct experiments to test hypothesis.
6. Reject or accept the hypothesis.
7. Document results, provide new scientific facts, and
apply them to support theory or greater understanding.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Step 1: Observe a spatial pattern of vegetative growth that is
different on the west side of each of the Hawaiian Islands than
on the east side.
Step 2: Formalize a hypothesis:
• Hypothesis 1 = Vegetation patterns are explained by rock
type.
• Hypothesis 2 = Vegetation patterns are explained by
temperatures.
• Hypothesis 3 = Vegetation patterns are explained by
rainfall.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Step 3: Select method of analysis. Use the big island of Hawaii
to map the specific 16 × 16 km (10 × 10 mi) square test
areas on the west and east sides of the island.
Step 4: Collect data:
• Vegetation maps from NASA satellites
• Geologic maps from USGS
• Temperature data from NOAA
• Collect rainfall data from NOAA services
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Step 5: Conduct experiments to test hypothesis:
• Overlay rock type on the vegetation map to look for
patterns.
• Look for correlation between rock type and vegetation
within grids.
• If hypothesis rejected, return to this step to test next
hypothesis.
Step 6: Reject or accept hypothesis:
• No correlation between rock type and temperature with
vegetation.
• Positive correlation between rainfall and vegetation.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Step 7: Document results and apply to theory:
• Documentation allows others to review for verification.
• If sufficient more tests conducted on other islands, the
hypothesis may be elevated to a theory.
• Theory = a hypothesis that has been tested and is
strongly supported by experimentation, observation, and
scientific evidence.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Courtesy NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Courtesy NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Courtesy NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Courtesy NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The World of Physical Geography
Geographic Use of the Scientific Method
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Courtesy NASA
The Shape of the Earth
Is the Earth round?
Courtesy NG Image Collection
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Courtesy NASA
The Shape of the Earth
The Earth is not a perfect
sphere:
• Equatorial diameter slightly
greater than polar diameter
• Poles = the two points on
the Earth’s surface where
the axis of rotation emerges
• Axis = an imaginary straight
line through the center of the
Earth around which the
Earth rotates
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Global Location
Geographic Grid
• Network of parallels and meridians used to fix location on
the Earth
© John Wiley & Sons
Meridian = north-south line
on the Earth’s surface,
connecting the poles
Parallels = east-west circle
on the Earth’s surface, lying
on a plane parallel to the
equator
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Location
Geographic Grid
© John Wiley & Sons
Equator is parallel of
latitude lying midway
between the Earth’s poles;
it is designated latitude 0º.
Intersection of meridians
and parallels makes up the
geographic grid.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Location
Geographic Grid
Latitude
• An angular distance for a
point north or south of the
equator, as measured from
the Earth’s center
• Like “ladders”
• Equator (0o) divides northern
and southern hemisphere
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Location
Geographic Grid
Longitude
• The angular distance for a
point east or west of the
prime meridian.
(Greenwich), as measured
from the Earth’s center.
• Prime meridian is 0o.
• Longitude measured
eastward or westward from
the prime meridian from 0o
to 180o.
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Location
Longitude
• Prime meridian runs through Greenwich, England.
© John Wiley & Sons
© Dennis di Cicco/Corbis
If we are facing north,
which side is to the east?
What is the latitude and
longitude of Point P?
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Time
Earth’s geographic grid and
the rotation of the Earth
help define global time.
Solar Time
• Based on Earth’s rotation
• Makes one full turn in a day
(24 hours)
• Sun rises in the east and
sets in the west
• Solar noon = reaches its
highest angle
• Solar timekeeping
© Frank Zullo/Photo Researchers, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Time
Solar Time
• Sun only shines on half of Earth at one time.
• Shines on eastern sides first.
• Local time is determined primarily by longitude.
When it is noon in Chicago,
is it earlier or later in:
a. Portland?
b. New York?
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Time
Standard Time
• Designated 24 standard meridians around the globe, at
equal intervals from the prime meridian.
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Time
Time Zones of the World
• Coordinated universal time (UTC)
• Bottom figure labels = number of hours of difference
between that zone and Greenwich mean time
• A negative 7 = seven hours behind Greenwich time
• A positive 3 = three hours ahead of Greenwich time
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Time
Time Zones of the World
© US Navy Oceanographic Office
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Time
Time Zones of the
Conterminous United
States
• Eastern, Central,
Mountain, and Pacific
• Daylight saving time
= clocks set ahead
(spring forward)
© John Wiley & Sons
If it is 3:00 PM in New York City, what time is it in:
a. Atlanta?
b. Dallas?
c. Los Angeles?
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Time
The International Dateline (IDL)
• Follows 180th meridian except through the Aleutian Islands,
Alaska and island nation of Kiribati
• Move east across IDL, subtract a day
© John Wiley & Sons
If you flew from Los Angeles to Beijing, would you add
or subtract a day?
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Global Time
Time Zones of the World
© John Wiley & Sons
If it is 7 AM Sunday, in New York, NY, what day and time
is it in Tokyo, Japan?
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Mapping the Earth
Map = a graphic, scaled
representative view of the
Earth, or any portion of the
Earth, as viewed from above,
depicting various features of
interest.
Cartography
• Subfield of geography
• Representing Earth
through maps
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Mapping the Earth
Map scale = the relationship between
distance on a map and distance on the
ground, given as a fraction or a ratio.
Three types of map scale:
• Verbal scale, such as 1 cm = 1 km
• Representative fraction
• 1:50,000 means that 1 unit of map
distance equals 50,000 units on the
Earth
• 1 cm on the map equals 50,000 cm or
500 m or 0.5 km on the ground
• Graphic scale
• Shows scale on a bar
• Stays accurate if map size changes
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Mapping the Earth
Map Scale
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Mapping the Earth
Map Projection
• A system of parallels and meridians represents the Earth’s
curved surface drawn on a flat surface.
• Curved surface cannot be projected onto a flat sheet
without distortion.
• Four main types
of projections:
• Cylindrical
• Conic
• Plane
• Elliptical (oval)
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Mapping the Earth
Cylindrical Projection
• Wraps a cylinder around the globe so that the paper
touches the globe at the equator.
• Parallels increases at higher latitude so that the spacing at
60°is double that at the equator, which distorts
landmasses, as seen with Greenland.
• Example: Mercator project
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Mapping the Earth
Plane Projection
• Produced by projecting a map from a center lit globe onto
a piece of paper touching the globe at any point.
• Can choose any center point, from which directions and
distances are true, but in outer areas, shapes and sizes
are distorted.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Mapping the Earth
Conic Projection
© John Wiley & Sons
• Cone sits atop the globe like
a cap, with the point of the
cone typically situated over
one of the poles.
• Accuracy is greatest along
the circle it touches—the
standard parallel.
• Good format for mapping
mid-latitude regions that are
larger east to west than
north to south.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Mapping the Earth
Elliptical (Oval)
Projection
• Central meridian and all
parallels are straight
lines, with relative sizes
represented accurately,
but shapes are distorted
at the edges.
• Often used for thematic
or political maps.
• Example: Mollweide
equal area map
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Mapping the Earth
Distortions in Map
Projections
• All maps are distorted.
• Mapmaker decides
whether to preserve
shape, size, or a
compromise.
• Conformity
© John Wiley & Sons
• True shape map preserves shape but distorts size.
• Example: Mercator projection
• Great Circle Route is the shortest distance between
two points.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Mapping the Earth
Distortions in Map Projections
• Equivalence: Equal-area projection
• Preserves size but distorts shape.
• Example: Goode’s projection
© University of Chicago Press
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Mapping the Earth
Distortions in Map Projections
• Compromises
• Sacrifice equivalency and conformity for the sake of
portraying a general balance between the two
• Example: Winkel Tripel projection
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Frontiers in Mapping Technologies
Remote-Sensing Tools
• Use of technology to record observations from a distance
(e.g., aerial images)
• Handheld, aircraft, and satellites capture radio waves,
microwaves, infrared energy, and visible wavelengths.
• Used for a variety of environmental and land-use issues
Population and
land use change
in Las Vegas
between 1973
and 2006.
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Frontiers in Mapping Technologies
Remote-Sensing Tools
• Spatial resolution = size of
the smallest area, or pixel
• Spectral resolution = range of
wavelengths captured by the
sensors
• Important Earth Observing
System (EOS) satellites:
• Landsat
• Weather satellites for
ozone, temperature,
clouds
• Terra
Courtesy of NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Frontiers in Mapping Technologies
Geographical
Information Systems
(GIS)
• A combination of
software, data, and
operational organization
• Provides the capacity to
capture and
communicate spatial
relationships among
geographic features,
values, and objects in
digital databases
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons
Frontiers in Mapping Technologies
Geographical Information Systems
(GIS)
• A useful analysis tool
• Designed to answer questions with spatial
information:
• What is the best route to deliver
packages?
• Which wells will be polluted by
underground aquifer contamination?
• What property values will suffer from
loan defaults in one neighborhood as
compared to another?
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Frontiers in Mapping Technologies
Geographical Information Systems
(GIS)
• Geocoding: These questions are
answered by merging conventional data
with their geographic locations.
• GIS maps are common feature in public
hearings.
© John Wiley & Sons
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Frontiers in Mapping Technologies
Global Positioning Systems (GPS)
• Accurately determines geographic location
• Consists of 24+ satellites that orbit Earth
• Receivers work by measuring and triangulating time delay
of signals from a minimum of three (usually four or more)
GPS satellites.
• Handheld devices and phones automatically enable GPS
data to be recorded.
• openstreetmap.org
• Represents a creative approach to citizen-led data
collection for mapping world’s streets
• Available for free
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Frontiers in Mapping Technologies
Geobrowsers and 3-D Mapping
• Internet mapping
• Uses:
• Reporting on humanitarian issues
• Tracking eco-disasters
1. What does a geographer see?
2. If the resolution of Blue Marble
is 1 square kilometer, how can
geographers keep track of 8.5
million points to discern changes
in land use?
Courtesy NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Frontiers in Mapping Technologies
Geobrowsers and 3-D Mapping
• Computer programs that access and query geographic
data draped over a computer-generated globe
• Google Earth
1. Explain how spaceage technologies have
affected the field
of geography.
2. What do you think
we can expect from
these technologies in
the future?
Courtesy NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Visualizing Physical Geography
by Timothy Foresman & Alan Strahler
Chapter 2
The Earth’s Global Energy Balance
© Zuma Press
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Chapter Overview
Electromagnetic
Radiation
Insolation over the Globe
Solar Energy and the
Earth’s Atmosphere
The Global Energy
System
© Zuma Press
What type of energy is
being captured?
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The Earth’s Global Energy Balance
Solar Energy
• Every second, the Sun
provides us with energy to meet
the world’s energy demands for
10 days!
• Currently, world economy is
driven by burning of fossil fuels,
which are nonrenewable.
• Solar energy is a fast-growing
industry.
© Zuma Press
Generating 64 megawatts of
solar thermal energy is the
Solar One power plant in
Nevada. Should we build more
solar plants? Explain.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Electromagnetic Radiation
• Electromagnetic radiation = wave form of energy radiated by
any substance possessing internal energy; it travels through
space at the speed of light.
• Wavelength is the measured distance separating one wave
crest from the next wave crest.
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Electromagnetic Radiation
Electromagnetic Spectrum
• Defines the entire range of wavelengths for all energy
Can you locate shortwave
(SW) radiation in the figure?
SW = energy in the range of
0.2 to 3 μm
Find longwave (LW) radiation.
LW = energy in the range of 3
to 5 μm
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Electromagnetic Radiation
Radiation and Temperature
•Hot objects radiate more energy
than cooler objects.
• Hotter objects emit shorter
wavelengths.
Can you locate
shortwave (SW)
radiation?
Find longwave (LW)
radiation.
LW = emitted from earth
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© University of Chicago Press
Electromagnetic Radiation
Solar Radiation
•Shortwave (SW) radiation
• Emitted from the sun
• Ultraviolet, visible, and infrared
radiation
• Distance of Earth’s orbit from
Sun optimal for life
• Solar constant
• Flow rate of solar energy
• Measured outside
atmosphere
• Watts/meter squared (W/m2)
© National Council for Geographic Education
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Insolation over the Globe
Energy received from the sun varies each day and over a
year, and it varies by latitude.
Daily Insolation
Insolation = flow rate of incoming solar energy, as measured
at the top of the atmosphere
Daily insolation depends on:
• Angle of sunlight:
• Subsolar point = noon Sun directly overhead at this one
point
• Declination = latitude of the subsolar point
• Day length
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Insolation over the Globe
Daily Insolation
• Day length also determines daily insolation
• Circle of illumination = separates day and night
• Equator always experiences 12 hours of day length
• Poles experience either 24 hours or 0 hours
• Other latitudes have varying day length each day
Considering
solar angle,
when is
insolation
greatest?
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Insolation over the Globe
Seasonal Change
• Earth revolves around the sun every 365.242 days:
• Orbit is counterclockwise and is an ellipse.
• Perihelion: point in orbit when Earth is closest to Sun.
• Aphelion: point in orbit when Earth is farthest from Sun.
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Insolation over the Globe
Seasonal Change
The Tilt of the Earth’s Axis:
• Earth has seasons because of the tilt of the axis.
• Axis aims toward Polaris
(North Star).
• Axis tilted at an angle of
23½° from a right angle
to plane of the ecliptic.
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Insolation over the Globe
Seasonal Change
Equinox: time when
subsolar point falls on
equator and circle of
illumination passes through
both poles
Winter solstice:
solstice occurring on
December 21 or 22,
when the subsolar
point is at 23½° S;
December solstice
Summer solstice:
solstice occurring on
June 21 or 22, when
the subsolar point is
at 23½° N; June
solstice
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Insolation over the Globe
Equinox
• Circle of illumination passes
through both poles
• Subsolar point at equator
• Day and night of equal
length everywhere on the
globe
• Occurs twice per year
• Vernal equinox: March 21
• Autumnal equinox:
September 23
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons, Inc.
Insolation over the Globe
Solstices
• Circle of illumination grazes Arctic and Antarctic Circles
• June solstice:
• North Pole has 24 hours
of daylight; day length
increases from equator
to North Pole.
• Arctic Circle is southern
point of 24 hours days.
• N hemisphere tilted
© John Wiley & Sons, Inc.
toward the sun.
• Subsolar point = 23.5°N
Is this the start of winter or
(Tropic of Cancer).
summer in the:
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
1. Southern hemisphere?
2. Northern hemisphere?
Insolation over the Globe
December Solstice
• South Pole has 24 hours
of daylight; day length
increases from equator to
South Pole.
• Arctic Circle is southern
point of 0 hour days.
• Northern hemisphere
tilted away from the sun.
• Subsolar point = 23.5°S
(Tropic of Capricorn).
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons, Inc.
Is this the start of winter or
summer in the:
1. Southern hemisphere?
2. Northern hemisphere?
Insolation over the Globe
Annual Insolation by
Latitude
• Annual insolation decreases
from equator (more direct
rays) to poles (oblique rays)
• Solar insolation is strongest
near the equator and
weakest near the poles
• Seasonal changes in day
length vary by latitude
© John Wiley & Sons, Inc.
At ___latitude, the solar
radiation would be spread out
over twice as much area as at
the equator.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Insolation over the Globe
Seasonal changes in day length by latitude
© John Wiley & Sons, Inc.
June solstice
• Farther north of equator,
the longer the days
• 12 hours at equator
• 24 hours at North Pole
December solstice
• Further north of equator,
shorter days
• 0 hours at South Pole
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Insolation over the Globe
The Earth’s Diverse Environments by
Latitudes
Latitude zones: decreasing insolation
from equator to poles
Equatorial: intense insolation, day
and night roughly equal
Tropical: high annual insolation
Subtropical: large annual insolation
© NG Image Collection
© NG Image Collection
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons, Inc.
Insolation over the Globe
The Earth’s Diverse Environments by
Latitudes
Midlatitude: strong seasonal contrasts
in insolation and length of day
© NG Image Collection
© The Image Works
Arctic/subarctic, Antarctic: enormous
variation in annual insolation, extreme
variation in day length
© John Wiley & Sons, Inc.
Polar: greatest change
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Composition of the
Atmosphere
• 97% lies within 30 km
(19 mi) or earth’s surface
© SPL/Photo Researchers, Inc.
Layers of the Atmosphere by Temperature
•Troposphere
• Lowest layer of the atmosphere, where human
activity and most weather takes place
• Temperature usually decreases with height
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Layers of the Atmosphere by Temperature
• Stratosphere
• Layer of atmosphere
directly above the
troposphere, where
temperature slowly
increases with height
© SPL/Photo Researchers, Inc.
• Ozone layer protects humans from ultraviolet radiation
• Mesosphere = coldest near top of this layer
• Thermosphere = hottest layer
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Layers of the Atmosphere by Composition
• Homosphere
• Heterosphere
© SPL/Photo Researchers, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Composition of the Atmosphere
Permanent gases
• 78% nitrogen
• 21% oxygen
• Argon
© John Wiley & Sons, Inc.
Variable gases
• Carbon dioxide (CO2): needed by green plants, absorbs
long-wave radiation
• Water vapor varies up to 2%, absorbs heat
• Ozone (O3): ozone layer in the stratosphere
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Aerosols = tiny particles present in the atmosphere that are
so small and light that the slightest air movements keep them
aloft.
•Global dimming:
• Reduction in industrial pollution has led to increase in
solar insolation.
• Decrease in atmospheric particles lowers the reflectance
of the Sun’s incoming energy.
• Temperatures may increase, adding to existing warming
trend.
© Science Central
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Absorption, Scattering, and Reflection
Absorption = process in which electromagnetic energy is
absorbed when radiation strikes molecules or particles in a
gas, liquid, or solid, raising its energy content.
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Absorption
• 16% of incoming solar radiation is absorbed in the atmosphere
• Carbon dioxide
• Water vapor holds latent heat
• Clouds absorb shortwave radiation
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Scattering
• Process by which particles and molecules deflect incoming solar
radiation in different directions on collision; atmospheric
scattering can redirect solar radiation back to space
• Diffuse radiation
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Reflection
• Albedo = proportion of solar radiation reflected upward
from a surface.
Intermediate albedo:
forests, fields, bare ground
© NG Image Collection
High albedo: Snow
and ice, also clouds
Albedo of water
depends on the
angle of incoming
radiation.
© Jeremy Woodhoue Masterfile
Low albedo: black
asphalt paving
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Solar Energy and the Earth’s Atmosphere
Reflection
• Losses of incoming
solar energy are much
lower with clear skies
(left) than with cloud
cover (right) because
clouds both reflect and
absorb solar radiation.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© A. N. Strahler
The Global Energy System
The Earth’s Energy Output
• Incoming energy
• Shortwave from the sun
• Greenhouse effect:
• Absorption of outgoing longwave radiation by
components of the atmosphere and reradiation
back to the surface, which raises surface
temperatures.
• Reradiation is also known as counterradiation.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The Global Energy System
Greenhouse Gases
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The Global Energy System
Why might the
greenhouse effect
be stronger in
humid regions,
such as the
Amazon Basin,
than in dry
regions?
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The Global Energy System
Greenhouse Effect
• Without the natural warming
process of the greenhouse
effect, the Earth would be too
cold for human habitation.
Enhanced Greenhouse Effect
• Levels of greenhouse gases in
the atmosphere increase as a
byproduct of human activities,
the greenhouse effect warms the
Earth more, disrupting our
climate.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons, Inc.
The Global Energy System
Net Radiation and the Global Energy Budget
• Net radiation is the difference between incoming and
outgoing radiation.
• Outgoing energy:
• Reflected SW
• LW radiation emitted
from earth
• Incoming energy:
• SW from the sun
© John Wiley & Sons, Inc.
• LW energy from greenhouse gases
• Net radiation increase has resulted in temperature
increase of about 1o C in the past century
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The Global Energy System
Human Impacts on the Global Energy Balance
1. Rising Concentrations of Greenhouse Gases
• Carbon dioxide (CO2):
• Trend since 1958
• Trend since 1860s
• Methane (CH4)
• Nitrous oxides (N2O)
2. Changes to surface
albedo
© John Wiley & Sons, Inc.
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
The Global Energy System
Human Impacts on the Global Energy Balance
3. Air Pollution
•
•
•
•
Hazy Asian Atmosphere
Asian Brown Cloud
10% reduction in crop yields
Dark soot particles had
lowered the albedo of snow
pack in the region
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© UNEP Assessment Report
Courtesy NASA
The Global Energy System
Human Impacts on the Global Energy Balance
4. Thinning of Ozone Layer in the Stratosphere
• Ultraviolet radiation is damaging to life, so, absorption
of UV radiation by ozone layer protects life on Earth’s
surface
• Does not impact warming
• Ozone hole
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Courtesy NASA
The Global Energy System
4. Thinning of Ozone Layer
Ozone hole forms through a
chemical process
• VERY cold air + CFCs
(human caused) + O3 =
Breakdown of O3
• Primarily forms over
Antarctica during their late
winter after it has been
very cold
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
© John Wiley & Sons, Inc.
The Global Energy System
4) Thinning of Ozone Layer
• Data collection:
• Aircraft (remote sensing)
• Balloons with sensors
• Satellites
Courtesy NASA
Courtesy NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.
Courtesy NASA
The Global Energy System
4. Thinning of Ozone Layer
• Montreal Protocol treaty
• 23 nations signed in 1987.
• By 1999, scientists confirmed
that concentrations had
topped out in 1997 and were
beginning to fall.
Why should the U.S.
government fund both
satellites and field work to
conduct climate change
research?
Courtesy NASA
Visualizing Physical Geography
Copyright © 2012 John Wiley & Sons, Inc.

Purchase answer to see full
attachment

Tags:
Geology

1200

User generated content is uploaded by users for the purposes of learning and should be used following Studypool’s honor code & terms of service.