Ch04

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.


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

4Figure 4-1b

Figure 4-1a


Energy, Heat, and Temperature

• Definition of energy• Forms of energy

– Chemical– Kinetic– Potential– Nuclear– Others

• Kinetic energy—energy of movement

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• Definition of temperature• Measuring temperature• Temperature scales

– Celsius– Fahrenheit– Kelvin– Conversions between scales

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Figure 4-2



• 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



• Electromagnetic energy• Electromagnetic spectrum• Wavelengths• Three important areas on

the spectrum– Visible radiation– Ultraviolet radiation

– Infrared radiation

• Shortwave solar radiation, insolation

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Figure 4-5


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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• Radiative processes• Absorption

– Body absorbs radiation– Good radiator, good

absorber• Reflection

– Objects repel electromagnetic waves

– Opposite of absorption

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Figure 4-7



• 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



• 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



• 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



• 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



• 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



• 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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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


The Heating of the Atmosphere

• Global energy budget

18Figure 4-17


Variations in Heating by Latitude and Season

• Angle of incidence• Atmospheric

obstructions• Day length• Latitudinal radiation

balance

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Figure 4-18


Variations in Heating by Latitude and Season

• World distribution of insolation

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Figure 4-21


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


Land and Water Contrasts

• Implications

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Figure 4-24


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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• 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



• 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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• 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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• 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


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


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



• 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



• Annual temperature range– Difference in average temperature of warmest and

coldest months

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Figure 4-32


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


Global Warming and the Greenhouse Effect

• Relationship between carbon dioxide and temperature

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Figure 4-35


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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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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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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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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