Lecture Notes: Global Wind Patterns

Introduction

• Topic: Global Wind Patterns
• Objective: Explain environmental factors that result in atmospheric circulation
• Key Factors:
  • Intensity of energy from the Sun
  • Properties of air (e.g., density)
  • Earth's rotation and the Coriolis effect
• Science Skill: Explaining relationships between environmental concepts and models visually

Properties of Air

• Density of Air:
  • Warm air is less dense than cold air, hence it rises.
  • Example: Temperature difference in a house between attic and basement.
  • Warm air holds more moisture.
• Process of Rising Air:
  • Warm air rises, cools, and expands.
  • Cooling causes moisture to condense and form precipitation (rain, snow, sleet).
  • After rising, air spreads and sinks at around 30 degrees north and south.
• Hadley Cell:
  • Cycle of air circulation between 0° and 30°.
  • Responsible for global wind patterns.

Energy from the Sun

• Sun's Impact:
  • Sunlight is most direct at the equator, causing air to warm and rise.
  • Rising air cools and moisture condenses, resulting in intense rainfall at the equator.
  • Expanding air moves outwards and sinks around 30° north and south, creating deserts.
• Pressure Systems:
  • High pressure at 30° due to sinking cool, dry air.
  • Low pressure at the equator due to rising warm air.
  • Air flows from high to low pressure, moving from 30° back to the equator.

Earth's Rotation and the Coriolis Effect

• Coriolis Effect:
  • Earth's rotation deflects moving objects (e.g., wind) in the opposite direction of rotation.
  • Example: Aiming a baseball from the North Pole deflects due to Earth's spin.
• Impact on Wind:
  • Wind deflected from east to west between 0° and 30° due to rotation.
  • Wind between 30° and 60° moves from west to east due to faster spin at 30°.
  • Comparison to treadmills: Faster momentum from faster-moving treadmill.

Global Wind Patterns

• Hadley Cell Overview:
  • Sun heats equator, air rises, sinks at 30°, moves towards 0° and 60°.
• Wind Directions:
  • Eastern trade winds from east to west between 0° and 30°.
  • Westerlies from west to east between 30° and 60°.
  • Influence on ocean currents and weather patterns.
  • North American weather comes from the west (e.g., Chicago, Wisconsin).

Conclusion

• Science Practice: Visual explanation of air circulation patterns.
• Reminder to utilize visual diagrams to understand and explain concepts.

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