Lecture on Forces Generating Winds

Introduction to Wind

• Wind is the transfer of mass in the atmosphere.
• Transfers surplus mass from high pressure to low pressure (deficit).
• Measuring pressure distribution is key for weather forecasting.
  • Weather maps use 'H' for high pressure and 'L' for low pressure.

Key Concepts in Wind

• Pressure: Force per area; related to mass and acceleration.
• Pressure Gradient: Difference in pressure between two locations.
  • Creates pressure gradient force.
• Wind Characteristics:
  • A vector with speed and direction.
  • Measured by anemometer (speed) and wind vane (direction).
  • Named after the origin direction (e.g., easterly wind comes from the east).

Types of Winds

• Cold Air Advection: North winds bring cold conditions.
• Moisture from South: South winds bring moisture, especially in Arizona.

Pressure Gradients

• Vertical Pressure Gradient: More extreme than horizontal; pressure decreases with height.
  • Balanced by gravity (hydrostatic balance).
• Horizontal Winds: Dominant due to hydrostatic balance.

Forces Affecting Wind Movement

• Pressure Gradient Force: Initiates wind motion.
• Coriolis Effect: Apparent force due to Earth's rotation:
  • Deflects moving parcels—right in northern hemisphere, left in southern.
  • Affects large-scale wind systems.

Global Wind Patterns

• Trade Winds: NE or SE, between 0-30 degrees latitude.
• Westerlies: SW or NW, between 30-60 degrees latitude.
• Easterlies: Between 60-90 degrees latitude.

Local Wind Patterns

• Thermal Low: Created by surface heating, leading to local winds.
• Land and Sea Breeze: Result of differential heating.
  • Sea Breeze: Daytime onshore wind.
  • Land Breeze: Nighttime offshore wind.
• Valley and Mountain Winds:
  • Valley Wind: Daytime upslope.
  • Mountain Wind: Nighttime downslope.

Monsoons

• Not thunderstorms; seasonal wind shifts.
• Occur on all continents except Antarctica.
• Arizona: Southerly winds bring moisture in summer.

Specific Wind Types

• Katabatic Winds: Downslope winds that warm and dry air.
  • Includes Chinook (Rockies) and Santa Ana (California).
  • Can cause fires and floods due to warm, dry conditions.

Environmental Impact

• Wind Power: Wind turbines generate electricity.
• Wind Damage:
  • Can cause soil erosion and physical damage.
  • Shelter belts can mitigate negative impacts by blocking or disrupting wind.

Conclusion

• Understanding wind dynamics aids in weather prediction and managing environmental impacts.