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Chapter 4: Insolation and Temperature
McKnight’s Physical Geography: A Landscape Appreciation,
Tenth Edition, Hess
© 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.
© 2011 Pearson Education, Inc.
Insolation and Temperature
• Mechanisms of Heat Transfer• Vertical Temperature Patterns• Global Temperature Patterns• Global Warming and the Greenhouse
Effect
3
© 2011 Pearson Education, Inc.
The Impact of Temperature on the Landscape
• All living things influenced by temperature
• Adaptation to temperature extremes
• Affects soil and bedrock exposure
4Figure 4-1b
Figure 4-1a
© 2011 Pearson Education, Inc.
Energy, Heat, and Temperature
• Definition of energy• Forms of energy
– Chemical– Kinetic– Potential– Nuclear– Others
• Kinetic energy—energy of movement
5
© 2011 Pearson Education, Inc.
Energy, Heat, and Temperature
• Definition of temperature• Measuring temperature• Temperature scales
– Celsius– Fahrenheit– Kelvin– Conversions between scales
6
Figure 4-2
© 2011 Pearson Education, Inc.
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
7
Figure 4-3
© 2011 Pearson Education, Inc.
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
© 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
9
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
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
11
Figure 4-9
© 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
12
Figure 4-12
© 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
13
Figure 4-13
© 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
14
Figure 4-14
© 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
15
Figure 4-15
© 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
16
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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
17
Figure 4-16
© 2011 Pearson Education, Inc.
The Heating of the Atmosphere
• Global energy budget
18Figure 4-17
© 2011 Pearson Education, Inc.
Variations in Heating by Latitude and Season
• Angle of incidence• Atmospheric
obstructions• Day length• Latitudinal radiation
balance
19
Figure 4-18
© 2011 Pearson Education, Inc.
Variations in Heating by Latitude and Season
• World distribution of insolation
20
Figure 4-21
© 2011 Pearson Education, Inc.
Land and Water Contrasts
• Land heats and cools more rapidly than water due to:– Specific heat– Transmission– Mobility– Evaporative cooling
21
Figure 4-23
© 2011 Pearson Education, Inc.
Land and Water Contrasts
• Implications
22
Figure 4-24
© 2011 Pearson Education, Inc.
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
23
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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
24
Figure 4-25
© 2011 Pearson Education, Inc.
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
25
© 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
26
© 2011 Pearson Education, Inc.
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
27
Figure 4-26
© 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
28
Figure 4-27
© 2011 Pearson Education, Inc.
Global Temperature Patterns
• Primary controls on global temperature– Altitude– Latitude– Land–Water contrasts– Ocean currents
29
Figure 4-29 – average January temperature
Figure 4-30 – average July temperature
© 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
30
Figure 4-31
© 2011 Pearson Education, Inc.
Global Temperature Patterns
• Annual temperature range– Difference in average temperature of warmest and
coldest months
31
Figure 4-32
© 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
32Figure 4-33
© 2011 Pearson Education, Inc.
Global Warming and the Greenhouse Effect
• Relationship between carbon dioxide and temperature
33
Figure 4-35
© 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
34
© 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
35
© 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
36
© 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
37