1. UNIT 3: Earth-Sun Relationships
Part 2: Circulation Patterns of the Atmosphere and the Oceans

2. The main function of the circulation of the atmosphere is to redistribute heat and moisture across the earth’s surface.
Atmospheric circulation accounts for about 87% of this heat distribution.
Wind is the movement of air relative to the earth’s surface.
The primary driving force behind air pressure and patterns is gravity.

3. Pressure describes the tendency of the air to rise or to sink at any given place or time.
Air tends to rise or sink as a result of its density.
Air density varies with altitude but, at the ground level, air density is governed by its temperature.
Thus, variations in radiation and temperature control pressure and wind.

4. Global Wind Patterns
Year-round heating in the equatorial region produces a thermal-low pressure belt.
This belt is known as the Equatorial Low or The Inter-Tropical Convergence Zone (ITCZ).
The ICTZ is home for tropical cyclones such as hurricanes. (You will learn about hurricanes in more detail in the next unit)
The ITCZ is located from 30°N to 30°S.
Other global wind patterns can be seen on slide 6. These are known as trade winds. These winds are the major driving force of weather around the world.
This slide contains a hyperlink.

5. The Inter-Tropical Convergence Zone

6. The Wind Patterns of the World

7. Another type of wind system is land/sea breezes.
This page contains hyperlinks

8. Land and Sea Breeze Diagram 2

9. Ocean Currents
Like trade winds, ocean currents also play a vital role in the weather around the world.
Both of these circulation patterns work together to determine the world’s weather and climate.
The oceans are a major transporter of heat from the equator to the polar regions.
There are two types of ocean currents:
1. Surface currents: make up 10% of all the ocean water
2. Deep water currents: make up 90% of all the ocean water

10. Ocean Currents Map

11. In conclusion, ocean currents are influenced by two main forces:
1. Primary forces: these forces start the movement of the water in the oceans.
A. Solar heating
B. Gravity
C. Winds
D. Coriolis Effect
2. Secondary forces: influence where the currents flow.
A. Surface winds affect the direction the ocean currents flow. (direct impact on tropical cyclones) B. Water at the equator is 8 centimeters higher than in the mid-latitudes creating a slope in which water flows down the slope.