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Understanding the Greenhouse Effect:. Synposis : Students plot diurnal temperature observations to compare the relative magnitude of the greenhouse effect under clear and cloudy-sky conditions. Understanding the Greenhouse Effect:. Learning Objectives :

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understanding the greenhouse effect
Understanding the Greenhouse Effect:
  • Synposis:Students plot diurnal temperature observations to compare the relative magnitude of the greenhouse effect under clear and cloudy-sky conditions
understanding the greenhouse effect1
Understanding the Greenhouse Effect:
  • Learning Objectives:
  • 1) Relate strength of the greenhouse effect to common experience
  • 2) Apply physical principles to characterize response to increased greenhouse gases
  • 3) Critically evaluate human-caused vs solar-caused hypotheses for recent warming.
the greenhouse effect fundamental questions context
The Greenhouse Effect:Fundamental Questions & Context
  • What is the Greenhouse Effect?
  • How big is the effect?
  • Why are cloudy nights warmer than clear nights?
the greenhouse effect

Electromagnetic (EM) radiation, radiation processes

  • “Clear Sky” Exercise
  • Earth-Sun System
  • Greenhouse Gases
  • “Cloudy Sky” Exercise

The Greenhouse Effect

background information
Background Information
  • Electromagnetic (EM) radiation
  • Solar and Terrestrial Emission
  • Radiation Processes and Interactions
  • Water Vapor is a Greenhouse Gas (selective absorpotion)
slide6

Central Project Question

Knowing that water vapor is a potent greenhouse

gas, what do you expect is the short-term effect of

cloud cover on your local temperature?

the greenhouse effect1

Electromagnetic (EM) radiation, radiation processes

  • “Clear Sky” Exercise
  • Earth-Sun System
  • Greenhouse Gases
  • “Cloudy Sky” Exercise
  • Earth vs Moon

The Greenhouse Effect

slide8

Clear Sky Anticipation Questions

For a weather station located at Des Moines, Iowa ,

consider the following questions regarding the diurnal

cycle during both winter (January) and summer (July).

  • Why does temperature change through the day?

2) Assuming a cloudless day, plot your expectations

for the diurnal cycle of temperature using the blank

template figure.

slide9

Hour of Day

Hour of Day

slide10

Anticipation Questions (continued…)

Diurnal cycle during both winter (January) and summer

(July) at Des Moines Iowa.

3) Indicate the time of sunrise and sunset in your

figure.

4) What, specifically, causes temperature to increase

or decrease?

5) How do summer and winter differ? Why?

slide11

Hour of Day

Hour of Day

slide12

Anticipation Questions (summary)

  • Diurnal cycle during both winter (January) and summer
  • (July) at Des Moines Iowa.
  • Indicate the time of sunrise and sunset in your

figure.

  • What, specifically, causes temperature to increase

or decrease?

  • How do summer and winter differ? Why?
slide13

Realization

Data Source:Airport at Des Moines, IA from 1945-2004 (NCDC Surface Airways)

Observation Variables:Temperature and cloud ceiling height (the height of the lowest cloud layer, if present)

  • Methodology:
  • Sort data and select only “clear sky” conditions
  • Compute the average diurnal cycle
  • Repeat for both January and July data
slide14

Hour of Day

Hour of Day

slide15

Clear Sky Contemplation

  • Why does temperature change through the day?
  • How does temperature decrease?
  • How do summer and winter differ?
the greenhouse effect2

Electromagnetic (EM) radiation, radiation processes

  • “Clear Sky” Exercise
  • Earth-Sun System
  • Greenhouse Gases
  • “Cloudy Sky” Exercise
  • Earth vs Moon

The Greenhouse Effect

radiation fundamental principles
Radiation: Fundamental Principles
  • All objects emit EM radiation; the wavelength and energy emitted depends on the object’s temperature
  • As Temperature increases,
  • total emission increases
  • As Temperature increases,
  • wavelength of peak emission decreases
solar and terrestrial radiation
Solar and Terrestrial Radiation

UV | Visible | IR

NOTE:

Log

Scale!

Sun

Earth

slide19

(No Atmosphere Case)

=

Earth,

Absorbed = Emitted

slide20

Solar Radiation

Terrestrial Radiation

“Radiative Equilibrium”

Incoming = Outgoing

Stable Temperature

the greenhouse effect3

Electromagnetic (EM) radiation, radiation processes

  • “Clear Sky” Exercise
  • Earth-Sun System
  • Greenhouse Gases
  • “Cloudy Sky” Exercise
  • Earth vs Moon

The Greenhouse Effect

greenhouse gases are

…“transparent” for sunlight

  • …only partially transparent to

Infrared Radiation (…from Earth’s Surface)

  • … “warmed” via radiation

(However, sensible heat and convection also

“warm” the atmosphere)

Greenhouse Gases are…

the greenhouse effect4

Electromagnetic (EM) radiation, radiation processes

  • “Clear Sky” Exercise
  • Earth-Sun System
  • Greenhouse Gases
  • “Cloudy Sky” Exercise
  • Earth vs Moon

The Greenhouse Effect

slide25

Cloudy Sky Anticipation Questions

Diurnal cycle during both winter (January) and summer

(July) at Des Moines Iowa.

1) How might temperature differ between clear and cloudy sky conditions?

2) Draw your expectations on the figure provided,

labeling the clear and cloudy sky lines.

slide26

Hour of Day

Hour of Day

slide27

Hour of Day

Hour of Day

slide28

Cloudy Sky Contemplation

  • Why is the cloudy sky temperature relatively flat?
  • How does clear sky temperature get both hotterand

colder than the cloudy sky temperature?

greenhouse process

Incoming

Solar

Earth’s Surface Emits

Infrared Radiation

Greenhouse Process
greenhouse process1
Greenhouse Process
  • Greenhouse Gases
  • Absorb IR
greenhouse process2
Greenhouse Process
  • Greenhouse Gases
  • Absorb IR
  • Emit IR
greenhouse process3
Greenhouse Process

NET EFFECT:

Earth’s surface

Warmed by

TWO

Heating sources

greenhouse process4
Greenhouse Process

What if we add

more Greenhouse

Gases??

TWO

Heating sources

the greenhouse effect5

Summary

  • GHGs absorb IR emitted by Earth’s Surface
  • The gases also emit IR back to the surface,

providing an additional heating source.

  • An example of this effect is the relative warmth of

cloudy nights.

  • Additional GHGs will increase surface temperature

in the same way as enhanced cloud cover.

The Greenhouse Effect

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