1. Chapter 4: Insolation and
Temperature
McKnight’s Physical Geography:
A Landscape Appreciation,
Tenth Edition, Hess

2. © 2011 Pearson Education, Inc.
Insolation and Temperature
• The Impact of Temperature on the
Landscape
• Energy, Heat, and Temperature
• Basic Heating and Cooling Processes in
the Atmosphere
• The Heating of the Atmosphere
• Variations in Heating by Latitude and
Season
• Land and Water Contrasts
2© 2011 Pearson Education, Inc.

3. © 2011 Pearson Education, Inc.
Insolation and Temperature
• Mechanisms of Heat Transfer
• Vertical Temperature Patterns
• Global Temperature Patterns
• Global Warming and the Greenhouse
Effect
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The Impact of Temperature
on the Landscape
• All living things influenced
by temperature
• Adaptation to temperature
extremes
• Affects soil and bedrock
exposure
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Figure 4-1b
Figure 4-1a

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Energy, Heat, and Temperature
• Definition of energy
• Forms of energy
– Chemical
– Kinetic
– Potential
– Nuclear
– Others
• Kinetic energy—energy of movement
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Energy, Heat, and Temperature
• Definition of temperature
• Measuring temperature
• Temperature scales
– Celsius
– Fahrenheit
– Kelvin
– Conversions between scales
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Figure 4-2

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Energy, Heat, and Temperature
• The Sun
• Primary source of energy
for Earth’s atmosphere
• Properties of Sun
– Average size star
– Nuclear fusion
– Magnitude of Sun’s
energy
• Energy spreads as it
leaves the Sun
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Figure 4-3

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Energy, Heat, and Temperature
• Electromagnetic energy
• Electromagnetic
spectrum
• Wavelengths
• Three important areas
on the spectrum
– Visible radiation
– Ultraviolet radiation
– Infrared radiation
• Shortwave solar
radiation, insolation 8
Figure 4-5

9. © 2011 Pearson Education, Inc.
Basic Heating and Cooling
Processes in the Atmosphere
• Radiation
– Definition
– Warmer objects radiate more effectively
– Warmer objects emit at shorter wavelengths
– Sun ultimate “hot” body in Solar System
– Blackbody radiators
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Basic Heating and Cooling
Processes in the Atmosphere
• Radiative processes
• Absorption
– Body absorbs
radiation
– Good radiator, good
absorber
• Reflection
– Objects repel
electromagnetic
waves
– Opposite of
absorption 10
Figure 4-7

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Basic Heating and Cooling
Processes in the Atmosphere
• Scattering
– Deflection of light
waves by molecules
and particles
• Transmission
– Electromagnetic
waves pass
completely through a
medium
– Sunsets
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Figure 4-9

12. © 2011 Pearson Education, Inc.
Basic Heating and Cooling
Processes in the Atmosphere
• Greenhouse effect
• Some atmospheric
gases transmit
shortwave radiation,
but not Earth’s
longwave radiation
• Earth radiation held in
by atmosphere
• Atmospheric blanket
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Figure 4-12

13. © 2011 Pearson Education, Inc.
Basic Heating and Cooling
Processes in the Atmosphere
• Other heating types
• Conduction
– Transfer of heat
energy across a
medium
– Results from
molecular collision
– Air is a poor
conductor
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Figure 4-13

14. © 2011 Pearson Education, Inc.
Basic Heating and Cooling
Processes in the Atmosphere
• Convection
– Heat transfer by
vertical circulation
– Molecules move in
tandem
– Convection cell
• Advection
– Horizontal transfer of
heat in a moving fluid
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Figure 4-14

15. © 2011 Pearson Education, Inc.
Basic Heating and Cooling
Processes in the Atmosphere
• Adiabatic cooling
– Air rises and expands,
molecular collisions
decrease, so
temperature
decreases
• Adiabatic warming
– Air sinks and
compresses,
collisions increase so
temperatures increase
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Figure 4-15

16. © 2011 Pearson Education, Inc.
Basic Heating and Cooling
Processes in the Atmosphere
• Latent heat
– Heat released or absorbed during a phase change
– “Latent” since heat is not felt
– Most common phase changes:
• Evaporation
• Condensation
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17. © 2011 Pearson Education, Inc.
The Heating of the Atmosphere
• Balance between
shortwave incoming solar
radiation and outgoing
longwave solar radiation
• Some shortwave
radiation reflected by
atmosphere or surface
• Albedo
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Figure 4-16

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The Heating of the Atmosphere
• Global energy budget
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Figure 4-17

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Variations in Heating by Latitude
and Season
• Angle of incidence
• Atmospheric
obstructions
• Day length
• Latitudinal radiation
balance
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Figure 4-18

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Variations in Heating by Latitude
and Season
• World distribution of
insolation
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Figure 4-21

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Land and Water Contrasts
• Land heats and cools
more rapidly than water
due to:
– Specific heat
– Transmission
– Mobility
– Evaporative cooling
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Figure 4-23

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Land and Water Contrasts
• Implications
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Figure 4-24

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Mechanisms of Heat Transfer
• Need heat transfer to
prevent constant
warming at tropics and
cooling at poles
• Circulation patterns in
atmosphere and oceans
transfer heat
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Mechanisms of Heat Transfer
• Atmospheric circulation
– General circulation
Ch. 5
• Oceanic circulation
– Respond to average
wind conditions over
long time scales
– Subtropical gyres
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Figure 4-25

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Mechanisms of Heat Transfer
• Northern and southern variations
– Near Northern Hemisphere pole, landmasses lie so
close that little flow can enter the Arctic Ocean
– Effect more pronounced in northern Pacific than
northern Atlantic
– In Southern Hemisphere, little land mass allows for
constant westward belt of ocean circulation, the
West Wind Drift
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26. © 2011 Pearson Education, Inc.
Mechanisms of Heat Transfer
• Temperature patterns
– Low-latitude currents are warm
– Poleward currents transfer warm water poleward
– High-latitude currents transfer warm water to the east in
Northern Hemisphere; cool water east in Southern
Hemisphere
– Equatorial currents transfer cool water equatorward
• Westward intensification
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Mechanisms of Heat Transfer
• Rounding out the pattern
– Northwestern portions of
Northern Hemisphere
receive cool water from
Arctic Ocean
– Water pulled away from
western coasts of
continents results in
upwelling
– Deep ocean circulation
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Figure 4-26

28. © 2011 Pearson Education, Inc.
Vertical Temperature Patterns
• Definition of lapse rate
• Environmental lapse rate
• Average lapse rate (about
6.5°C/km)
• Temperature inversions
– Surface inversions
– Upper air inversions
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Figure 4-27

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Global Temperature Patterns
• Primary controls on global
temperature
– Altitude
– Latitude
– Land–Water contrasts
– Ocean currents
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Figure 4-29 – average January temperature
Figure 4-30 – average July temperature

30. © 2011 Pearson Education, Inc.
Global Temperature Patterns
• Seasonal patterns
– Latitudinal shift in
isotherms from one season
to another
– More pronounced over
continents than water and
over high latitudes than low
latitudes
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Figure 4-31

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Global Temperature Patterns
• Annual temperature range
– Difference in average temperature of warmest and
coldest months
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Figure 4-32

32. © 2011 Pearson Education, Inc.
Global Warming and the
Greenhouse Effect
• Climate of Earth is becoming warmer, known as global
warming
• Human-enhanced greenhouse effect
• Carbon dioxide main culprit
• Also methane, nitrous oxide
• Intergovermental Panel on Climate Change
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Figure 4-33

33. © 2011 Pearson Education, Inc.
Global Warming and the
Greenhouse Effect
• Relationship between carbon dioxide and temperature
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Figure 4-35

34. © 2011 Pearson Education, Inc.
Summary
• Temperature affects both living and nonliving aspects of
Earth’s landscape
• Energy exists in many different forms, but cannot be
created or destroyed
• Temperature is a measure of the amount of kinetic
energy in the molecules of a substance
• Temperature is measured on three primary scales
• The Sun is the primary source of energy for Earth’s
atmosphere
• Electromagnetic radiation is classified by wavelength
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35. © 2011 Pearson Education, Inc.
Summary
• The Sun emits three important types of electromagnetic
radiation: visible, infrared, and ultraviolet
• Insolation refers to incoming solar radiation
• Radiation is the process by which electromagnetic
radiation is emitted by an object
• Radiation can undergo several processes, including
absorption, reflection, transmission, and scattering
• The greenhouse effect makes Earth able to support life
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36. © 2011 Pearson Education, Inc.
Summary
• Conduction is the transfer of heat through molecular
collision
• Convection is a vertical transport of heat in a fluid
• Advection is the horizontal transport of heat
• Adiabatic cooling and warming processes do not release
or absorb heat
• The global radiation budget describes the latitudinal
distribution of temperature
• Land surfaces heat and cool faster than water surfaces
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37. © 2011 Pearson Education, Inc.
Summary
• Heat is transferred globally through atmospheric and
oceanic circulations
• The vertical temperature patterns in the atmosphere
help describe vertical circulations
• Global warming is the observed warming of the
atmosphere
• Temperature and carbon dioxide show a close
relationship
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