Lecture Notes: Atmospheric Circulation and Wind Scales

Key Concepts

• Air Movement:
  • Air moves from high pressure to low pressure.
  • Wind patterns are influenced by pressure gradients, the Coriolis effect, and friction.

Air Pressure and Wind Dynamics

• Chapter 6 Recap:
  • Air pressure differences cause wind.
  • Winds curve into low pressure in a counterclockwise fashion due to convergence at the surface.
  • Convection causes air to rise, leading to surface convergence.
• Heat Distribution:
  • Equator receives most heat due to surplus solar energy.
  • Low pressure areas form around equator due to rising warm air.

Global Wind Patterns and Circulation

• Chapter 7 Focus:
  • Understanding global atmospheric circulation patterns.
  • Examines wind flows at different latitudes and regions.

Scales of Motion

• Macro/Planetary Scale:
  • Long wave patterns in the westerlies, covering thousands of miles.
• Synoptic Scale:
  • Weather maps scale, includes cyclones and anticyclones.
• Mesoscale:
  • Includes thunderstorms, tornadoes, land and sea breezes.
  • Shorter geographic and temporal scales.
• Micro Scale:
  • Small-scale motions like wind gusts and microbursts.
  • Very brief and localized.

Wind Flow and Patterns

• Hadley Cell:
  • Air rises at equator, creating low pressure (equatorial low/ITCZ).
  • Northeast trade winds converge at equator.
  • Subtropical highs at 30°N and 30°S.
• Westerlies and Polar Winds:
  • Westerlies dominate US from 30°N to 60°N.
  • Polar easterlies flow from high pressure at poles.

Regional Wind Features

• Sea Breezes:
  • Caused by differential heating between land and sea.
  • Converging air from ocean to land leads to convection and potential cloud formation.
• Horse Latitudes:
  • Areas of high pressure and light winds around 30°N.
  • Historical reference to sailors lightening ships by throwing horses overboard.

Jet Stream Dynamics

• Jet Stream:
  • Fast-moving winds at about 30,000 feet.
  • Separates cold polar air from warm tropical air.
  • Stronger in winter due to greater temperature differences.

Weather Systems and Forecasting

• High and Low Pressure Systems:
  • Low pressure: converging surface winds, rising air, cloud formation.
  • High pressure: diverging winds, sinking air, generally clearer weather.
• Weather Maps and Synoptic Scale:
  • Use isobars to show pressure systems and wind flow.
  • Synoptic maps illustrate large-scale weather patterns.

Global Atmospheric Influence

• Seasonal Shifts:
  • Movement of pressure belts with solar radiation changes.
  • Influences regional climate and weather patterns.
• Precipitation Patterns:
  • More precipitation near equator and polar fronts.
  • Dryer conditions under high-pressure zones.

Study Resources

• Chapter 7 Pages 195-205:
  • Detailed diagrams and explanations of global circulation patterns.
  • Use diagrams to understand different wind flows and their effects on weather.