Introduction to Wind and Atmospheric Circulation

Introduction to Wind and Circulation

• Excitement about covering wins and introducing the concept of global circulation of winds.

• Mention of local winds and their effects during the course.

• Availability of a study guide on Canvas for further preparation before the exam.

Defining Wind

• Wind defined as the horizontal movement of air across the Earth's surface.

• Air treated as a fluid in physics; heavier air sinks while lighter air rises.

• Importance of convection and advection principles as air behaves similarly to water in heating and movement.

• Winds named for the direction they originate from (e.g., easterlies blow from the east toward the west).

• Distinction made between prevailing winds and occasional local winds; prevailing winds generally dominate conditions in a specific location.

Mechanisms of Wind Creation

Driving Forces

1. Pressure Gradient: Difference in atmospheric pressure across space leading to air movement.

   • Basic rule: air pressure decreases with elevation.

   • Irregularities in air pressure can produce wind; thus understanding pressure is crucial.

   • Measurements of air pressure using barometers (normal range: 980 - 1050 millibars). Hurricane low pressure example.

2. Coriolis Effect: The apparent deflection of wind due to the Earth's rotation.

   • In the Northern Hemisphere, winds bend to the right; in the Southern Hemisphere, they bend to the left.

   • The effect becomes more pronounced with faster winds, impacting the direction but not the speed of the winds.

3. Friction: The resistance encountered by air moving across the Earth's surface.

   • Slows down wind speeds, especially near the surface, and alters the Coriolis effect.

   • In the upper atmosphere with no friction, winds follow the pressure gradient and Coriolis effect only.

Interaction of Forces

• Explanation of how these forces influence wind movement:

  • Winds blow from high-pressure areas to low-pressure areas.

  • Air can rise when it warms and cools when it sinks, creating patterns of low and high pressure across regions.

  • Example of air sinking creates areas of high pressure, potentially leading to clearer skies, while rising air could indicate stormy weather due to cooling and moisture.

Development of Local Winds

• Local winds typically occur due to small pressure differences and can change rapidly based on local conditions.

• Larger scale patterns, such as global circulation, are influenced by consistent temperature gradients and geographic factors.

• Example of storms influencing regional weather changes dramatically.

Global Wind Patterns

• Explanation of how global circulation patterns are established and can affect local weather.

• The formation of cyclones and anticyclones associated with high and low pressure areas respectively.

• Visual representation of isobars on a pressure map showing sharp gradients leading to varying weather conditions.

Understanding Pressure Maps

• Each weather station collects data, allowing for analysis of high and low-pressure areas using isobars.

• Isobars indicate pressure variations; closely spaced isobars hint at stronger winds due to steeper pressure gradients.

• High-pressure systems typically lead to calm weather, while low-pressure systems correlate with stormy conditions.

Summary of Forces Affecting Wind

• To sum up, winds are primarily influenced by:

  1. Pressure gradients.

  2. The Coriolis effect, which modifies trajectories.

  3. Friction, which alters wind speed close to the surface.

• Understanding these forces is critical for predicting weather patterns and local winds effectively.

Conclusion

• Greater knowledge of wind dynamics and pressure systems can lead to more accurate weather forecasting.

• Collaboration among geography, physics, and weather studies is essential for a comprehensive grasp of atmosphere and wind patterns.