Wednesday April 4, 2012

1. WednesdayApril 4, 2012 (Discussion & Worksheet – The Structure of the Atmosphere; Earth-Sun Relationships)

2. The Launch Pad Wednesday, 4/4/12 NOTE: Put this on your green worksheet to answer Question #1 Which of the following components of our atmosphere would you consider to be disadvantageous, and why? nitrogen oxygen argon carbon dioxide too much causes the greenhouse effect water vapor smog air quality pollutant smoke air quality pollutant dust air quality pollutant

4. Announcements • I will be available after school today until 5:00.

5. Latest News Extreme Weather Threatens Rich Ecosystems Click below for article: http://www.sciencedaily.com/releases/2012/03/120330110535.htm

6. Worksheet The Structure of the Atmosphere; Earth-Sun Relationships

7. The Structure of the Atmosphere The atmospheric pressure at any point is the weight of the air above that point. The average sea level pressure is slightly more than 1,000 millibars, or about 14.7 pounds per square inch. Atmospheric pressure decreases with altitude. One-half of the Earth’s atmosphere is below 3.5 miles in altitude. Ninety percent of our atmosphere is below 10 miles.

8. Atmospheric Pressure Variation with Altitude Figure 16.6

9. The Structure of the Atmosphere Earth’s atmosphere can be layered based upon temperature. The troposphere is the bottom layer. As you ascend into the atmosphere, temperature decreases with altitude, which is referred to as the environmental lapse rate. 6.5˚C per kilometer, or 3.5˚F per 1,000 feet is the average lapse rate for temperature. Our atmosphere’s thickness varies, but is on average height about 12 km. The outer boundary of the atmosphere is called the tropopause.

10. The Structure of the Atmosphere Earth’s atmosphere can be layered based upon temperature. The stratosphere extends from an altitude of about 12 km up to about 50 km. Temperature increases at the top of the stratosphere. The stratosphere’s outer boundary is named the stratopause. The mesosphere begins at an altitude of about 50 km and climbs up to about 80 km. Here the temperature decreases again. The outer boundary of the mesosphere is named the mesopause.

11. The Structure of the Atmosphere Earth’s atmosphere can be layered based upon temperature. Above the mesosphere is the thermosphere, which has no well-defined upper limit. Just a tiny fraction of our atmosphere’s mass is in this region, with gases moving at high speeds.

12. Thermal Structure of the Atmosphere Figure 16.8

13. Earth - Sun Relations Remember from our study of astronomy that the Earth has two major motions: Earth rotates (spins) on its axis once every 24 hours. Earth also revolves (orbits) around the Sun once every 365.25 days. What causes our seasons is the changing Sun angle through the Earths yearly revolution cycle. In addition, there is a change in the length of daylight hours throughout the year.

14. Relationship of Sun Angle to the Path of Solar Radiation Figure 16.12

15. Relationship of Sun Angle and Solar Radiation Received Figure 16.11

16. Earth - Sun Relationships Figure 16.13

17. Daily Paths of the Sun at 40º N Latitude Figure 16.10 A

18. Daily Paths of the Sun at 40º N Latitude Figure 16.10B

19. Daily Paths of the Sun at 40º N Latitude

20. Earth - Sun Relations Thus, the seasons are caused by Earth’s changing orientation to the Sun throughout the year, and the fact that Earth’s axis is inclined 23½º, and the axis is always pointed in the same direction. Here are some special days in the Northern Hemisphere: At the Summer solstice (June 21–22), the Sun’s vertical rays are located at the Tropic of Cancer (23½º N latitude.) At the Winter solstice (December 21–22), the Sun’s vertical rays are located at the Tropic of Capricorn (23½º S latitude.) At the Autumnal equinox (September 22–23), the Sun’s vertical rays are located at the Equator (0º latitude.) At the Spring (Vernal) equinox (March 21–22), the Sun’s vertical rays are located at the Equator (0º latitude.)

21. Characteristics of the Solstices and Equinoxes Figure 16.14

23. Multiple exposures of the midnight Sun in late June or July in high northern latitudes.

24. Average monthly temperatures for six cities located at different latitudes. Note that Capetown, South Africa, experiences winter in June, July, and August.