CONVECTION IN THE ATMOSPHERE

1. Convection Requires: A Fluid Differential Heating Convection Produces: Low and High Pressure Zones Climate Zones Winds Rain-Shadow Desert Ocean Currents CONVECTION IN THE ATMOSPHERE

2. MOLECULAR DESCRIPTIONS of SOLIDS, LIQUIDS, AND GASSES SOLIDS LIQUIDS GASES ************************************************ Connected Not Connected Not Connected Close Together Close Together Far Apart ************************************************ Fluids are matter that have the property that their molecules are not well connected. Both liquids and gasses are fluids. Convection only occurs in fluids because connections stop convection.

3. Convection Requires Differential Heating • On our globe, areas nearer to the equator receive more heat energy per unit area. • As a result, convection occurs on a global scale on our planet. • Convection makes weather.

4. Convection Requires Differential Heatingand also Occurs on a Local Scale Differential heating occurs near bodies of water because the heat capacity of water is higher than dirt and rock. During the day, the land heats up faster than water. This makes air rise over faster land than water and causes a convection cell. At night, the land cools more quickly, and then the air over water is warmer so the air over the water rises. The same phenomenon occurs seasonally, making colder weather come later near bodies of water and slowing the arrival of warm water.

5. Convection Requires Differential Heatingand also Occurs on a Local Scale During the night, the air around mountain tops cools more rapidly than air in the valleys. The cooled air has a higher air pressure than the warmer air. The cooled air then moves down the valley causing a “mountain breeze.” During the day, the air above the mountain tops heats up more rapidly than the air in the valleys. Because of this uneven heating, the direction of the air flow is reversed, making a “valley breeze.” This local pattern is called a “convection cell.”

6. The Convection Process Convection currents transport heat energy from near the earth’s surface, into the troposphere.

7. The Convection Process Convection occurs in a fluid, with differential heating. The hottest part rises and cooler fluid takes its place. In the atmosphere, air rises (low pressure) spreads towards the poles, (cold area) falls (high pressure), and returns to the rising location (causing winds).

8. Convection Patterns Make Low Pressure Zones • Low pressure occurs when air rises. • Low pressure is generally associated with clouds, precipitation, and grumpiness. • When a zone has consistently low pressure, it becomes a tropical or temperate rain forest. • Winds blow towards low pressure areas.

9. Convection Patterns Define High Pressure Zones • High pressure occurs when air is falling. • High pressure gives generally clear weather and cheerful moods. • Consistent high pressure zones make deserts, such as those between 20 and 30 deg North and South latitude. • Winds blow away from high pressure areas.

10. CONVECTION DEFINES CLIMATE ZONES AND WIND PATTERNS Each convection loop defines a climate zone: Tropical, Temperate, and Polar. There are three loops instead of one, because of the earth’s spin.

11. Convection Causes Mountain and Valley Winds. Compare the pictures. Describe in words the differential heating pattern. Describe the convection process for that situation, and how different winds result.

12. Convection Causes Land and Sea Breezes Compare the pictures. Describe in words the differential heating pattern. Describe the convection process for that situation, and how different winds result.

13. Convection Makes a Rain-Shadow Desert

14. Convection Causes Ocean Currents Note that warm currents tend to head away from the equator and towards the poles. Cold currents tend to head from the poles to the equator. Why?