Global Wind Belts and Jet Streams

Overview

• Focus: Actual wind belts resulting from global pressure differences.
• Background Concepts: Rising and descending air, temperature-driven cells (Hadley cells, polar cells), and the Coriolis effect.

Main Wind Belts

• Trade Winds: Blow east to west between 0° and 30° latitude.
• Westerlies: Blow west to east between 30° and 60° latitude, dominant in the US.
• Polar Easterlies: Blow east to west near the poles.

Intertropical Convergence Zone (ITCZ)

• Located around the Equator where the Northeast and Southeast Trade Winds converge.
• Characterized by rising warm, humid air leading to heavy rainfall and cloud formation.
• ITCZ shifts seasonally: moves north during Northern Hemisphere summer and south during winter.

Subtropical Highs

• Areas where air descends, leading to suppressed cloud development and low precipitation.
• Associated with major world deserts (e.g., Sahara, Mojave, Atacama).

Global Pressure Belts and Winds

• Horse Latitudes (30°-35°): Variable winds due to the meeting of Westerlies and Trade Winds.
• Westerly Winds: Dominant across much of the US, influencing weather systems to move west to east.
• Surface Winds: Influenced by high-pressure systems, major deserts, and cold water currents.

Jet Streams

• Definition: High-velocity air currents along boundaries of air masses and dominant wind belts.
• Types: Subtropical Jet and Polar Jet.
• Effects on Weather: Influence the extent of cold and warm air masses across continents, affecting weather patterns like thunderstorms and tornadoes.
• Impact on Aviation: Jet streams can alter flight times.

Concepts Behind Jet Stream Velocities

• Steep Pressure Gradient: Leads to high wind speeds in jet streams.
• Conservation of Angular Momentum: Smaller radii of curvature in air flow increase velocity, much like a spinning ice skater.

Key Takeaways

• Wind belts are crucial for understanding weather patterns and climate systems across the globe.
• Rising and sinking air, along with the Coriolis effect, create distinct wind belts and pressure systems.
• The jet stream plays a significant role in weather forecasting and understanding climate dynamics.