1. Chapter 17: The Atmosphere: Structure & Temperature
17:1 Atmosphere Characteristics

2. Weather What is weather? What is climate?
Weather is constantly changing, and it refers to the state of the atmosphere at any given time and place. It is a day to day condition.
Weather conditons in a certain area averaged oer a long period oft time.
What is the climate of Knightdale?
Hot and humid

3. Climate

4. Most Important Measurable Properties of Weather & Climate
Air Temperature
Humidity
Type and amount of precipitation
Rain, sleet, snow
Others?

5. Composition of the Atmosphere
What are the major components of the air?
Nitrogen makes up about 78% of our air
Oxygen makes up about 21% of our air

6. Temperature Changes The atmosphere is divided into four layers
Ozone layer

7. Layers of the Atmosphere
Troposphere – 1st layer
Called “weather layer “ because all weather occurs here
Has temperature to sustain life , average 70 degrees F
Stratosphere – 2nd layer
Ozone layer is concentrated here
Ozone combines three oxygen atoms into each molecule (O3)
Ozone absorbs UV rays from the Sun
Without ozone layer we would see an increase in skin cancer
Without ozone, our planet would be uninhabitable for many living organisms

8. Layers of the Atmosphere
Mesosphere – 3rd layer “middle layer
Temp decreases with height
More than 80 km above the Earth
Temps here approach –90 degrees C
Thermosphere – 4th layer- “thermo” means heat
Contains only a fraction of the atmosphere’s mass
Temps increase here b/c oxygen and nitrogen absorb short wave, high energy solar radiation

9. Ozone Layer The ozone layer is crucial to life on earth
What does ozone do for you?
Ozone absorbs potentially harmful UV radiation from the sun
If ozone did not filter most UV radiation and all the sun’s UV rays reached the surface of the earth, our planet would be uninhabitable for many living organisms
How is Ozone destroyed?
Propellants (CFCs) in spray cans break down ozone

10. Primary Pollutants What is the major pollutant in our atmosphere?
Primary pollutants are emitted directly from from identifiable sources
Emissions from transportation account for nearly 50% of primary pollutants in atmosphere
Carbon Monoxide

11. Air Pollutants
Air pollutants are air borne particles and gases that occur in concentrations large enough to endanger the health of organisms

12. Temperature Changes
The pictures of snow capped mountains rising above snow free valleys show us that Earth’s atmosphere becomes colder as you climb higher

13. Earth-Sun Relationships
What drives the Earth’s weather and climate? How?
Solar energy is not distributed evenly over Earth’s surface. These are caused by the motions of Earth relative to the Sun and by variations in Earth’s land and ocean surfaces
The Sun, the uneven heating of the Earth

14. Earth & Sun Relationships
Earth has two principal motions
Rotation – the spinning of Earth about it’s axis
Revolution – the movement of Earth in it’s orbit around the Sun

15. Earth’s Orientation
We know that it is colder in winter than summer, but why?
Earth is tilted on it’s axis – 23.5 degrees
What would happen if the Earth was not tilted?
- Length of day and a gradual change in the angle of the noon sun above the horizon affect the amount of energy the Earth receives
- We would not have any seasons…

16. Earth’s Tilt & Sun’s Rays

17. Alaska… Summer Solstice
This is the midnight summer solstice – June 21st

18. Solstices
On June 21st each year the axis is such that the Northern Hemisphere is “leaning” 23.5 degrees toward the Sun
This is known as the summer solstice, or first “official” day of summer
December 21st – Northern Hemisphere is “leaning” 23.5 degrees away from the Sun
Winter Solstice – first “official” day of winter

19. Solstices & Equinoxes

20. Equinoxes March 21st September 22nd
Spring (Vernal) Equinox
September 22nd
Autumnal Equinox
Both – the Sun’s rays are hitting the equator, right on the money & the time of actual daylight equals the time of no daylight