COM GEOGRAPH​Y
  • Home
  • Geography Programs in CA
  • Career Opportunities
  • GEOG 102
  • Chapter 8: Environmental Issues
  • Home
  • Geography Programs in CA
  • Career Opportunities
  • GEOG 102
  • Chapter 8: Environmental Issues
Search by typing & pressing enter

YOUR CART

Section 1- Ch 2: Solar Radiation and the Seasons

CHAPTER TWO OBJECTIVES
  • Identify the types of energy and how they can be transmitted.
  • Describe the characteristics of solar radiation.
  • Explain the influences of solar angle on solar radiation receipt at the surface.
  • Describe how seasonal changes in solar energy vary with latitude.
  • Recognize the characteristics of Earth’s orbit around the Sun and how they create the seasons.
Picture

Greetings Weather Enthusiasts!
In lecture class during Week 3, we covered the Geographic Grid, Earth-Sun Relationships, Energy, Power, and the different forms of Energy Transfer - Radiation, Conduction, and Convection.

RADIATION CHARACTERISTICS

PictureThe Electromagnetic Spectrum
Radiation is the transfer of energy requiring no physical medium (can occur through empty space). Radiation is continually emitted by all substances. When you snuggle up with a loved one (human or animal) you can feel their radiating heat. We get the bulk of our energy from the Sun’s radiation, and it is this reception of radiation that is THE DRIVING FORCE for virtually all processes we will discuss in this course.

​Radiation comes in the form of ELECTROMAGNETIC WAVES, because the radiation is composed of bpth electric and magnetic waves. Two properties of waves are their amplitude and wavelength.
  • Amplitude refers to the height of the wave crest. Radiation quantity refers to amount of energy transferred, and is associated with wave amplitude. Everything else being equal, the amount of energy being transferred is directly proportional to wave amplitude
  • Wavelength is the distance from crest to crest (or trough to trough). Radiation wavelength relates to radiation quality:
    • Wavelength identifies the type of radiant energy (X-ray, Gamma, Microwave, etc.)
  • All electromagnetic radiation travels at the speed of light (300K km/s or 186K mi/s . It takes about 8 minutes for the Sun’s energy to reach us. For the next nearest star, it's about 4.3 years!

There’s an infinite # of wavelengths…
  • Just like the Sun (video), All objects radiate energy in a # of wavelengths
  • We are concerned with wavelengths on the magnitude of MICROMETERS = 1 millionth of a meter


PictureThe Electromagnetic Spectrum
There are Physical laws defining amount and wavelength of emitted energy and they apply to hypothetical perfect emitters of radiation known as blackbodies. The Earth and Sun are similar to blackbodies.There are TWO LAWS you should be familiar with:
  1. (Stefan-Boltzmann law) The intensity of radiation depends on the temperature raised to the fourth power; and
  2. Wien’s law For any radiating body, the wavelength of peak emission (in micrometers) is given by Wien’s law.

  • The MAIN POINTS to gather from these laws is the following: 
    • The Sun emits high intensity short-wave radiation: < 4um = shortwave
    • The Earth emits low intensity long-wave radiation: > 4 um = longwave
SLIDE: Fig. 2-8 Note the AXES and UNITS!


SOLAR CONSTANT

How much solar energy reaches the Earth? We know this amount, it’s called the Solar Constant. The Solar Constant is the average amount of solar energy received at the top of Earth’s atmosphere: 1367 W/m3. 

Remember Perihelion and Aphelion? When the Earth is closest to the Sun in its orbit, it receives more energy, and when it is further away, less. It’s not that a beam of energy loses intensity as it moves through space, it’s that the same beam of energy is distributed over a larger and larger area, making it less effective at warming or illuminating. 
Picture
Reduction of Energy Received Due to Distance
CLICK FOR CHAPTER 3

TERMS

  • energy and power
  • joule and watt
  • electromagnetic  radiation
  • wavelength
  • shortwave and longwave radiation
  • Stefan-Boltzmann law
  • Wien’s law
  • solar constant
  • insolation
  • kinetic energy
  • potential energy
  • conduction
  • convection
  • radiation
  • buoyancy
  • ecliptic plane
  • revolution
  • rotation
  • perihelion and aphelion
  • Polaris
  • solstice (June and December)
  • equinox (March and September)
  • Tropics of Cancer and Capricorn
  • Arctic and Antarctic Circles
  • subsolar point
  • solar declination
  • beam spreading

PREPARE FOR YOUR QUIZ

To check for understanding, you will take a short quiz on Chapter 2. You will have two chances to take the quiz on Moodle, and I will record your highest score. Review the following to prepare for the quiz:
  • What are the '5' Reasons for the Seasons we covered in class?
  • What is Aphelion and Perihelion, and when do they occur?
  • Compare and contrast Radiation, Conduction and Convection.
  • Be able to differentiate between Potential and Kinetic Energy.
  • At what speed does electromagnetic radiation travel, and how long does it take to get from the Sun to the Earth?
  • What is the relationship between the location of the Subsolar Point (Solar Declination) and the Solstices and Equinoxes?
  • What does the Stefan-Boltzman law tell us?
  • What does Wien's Law tell us?
Home
About
Contact