Chapter 4: Global Climates and Biomes

Module 10: Air Currents

Objectives:

• Explain how the properties of air affect its movement in the atmosphere.

• Identify the factors that drive atmospheric convection currents.

• Describe how Earth’s rotation affects air currents.

• Explain how air movement over mountain ranges impacts climates.

Air Currents

• Wind connects most life on Earth.

  • Keeps tropics from being unbearably hot.

  • Prevents the rest of the world from freezing.

Important Properties of Air:

• Saturation point: Maximum amount of water vapor at a given temperature.

• Adiabatic cooling: Cooling effect of reduced pressure on rising air.

• Adiabatic heating: Heating effect of increased pressure on descending air.

• Latent heat release: Energy released when water vapor condenses into liquid water.

Atmospheric Convection Currents

• Convection current process: Warming at the surface causes air to rise, cool, and ultimately sink, completing the cycle.

Types of Convection Cells:

• Hadley cell: Between the equator and 30° N and S.

• Intertropical convergence zone (ITCZ): Latitude receiving most intense sunlight, where Hadley cells converge.

• Polar cell: Rises at 60° N and S; sinks at the poles.

• Ferrell cell: Lies between Hadley and Polar cells.

Coriolis Effect

• Earth's rotation causes deflection of moving objects.

  • Faster rotation at the equator affects wind patterns.

• Coriolis effect: Deflection of wind patterns.

Rain Shadows

• Rain shadow: Dry conditions on the leeward side of mountains due to humid winds causing precipitation on the windward side.

• Process:

  • Humid winds rise and cool at the windward side.

  • Precipitation falls, leading to dry air on the leeward side due to adiabatic heating.

Module 11 Ocean Currents

Learning Objectives:

• Describe the patterns of surface ocean circulation.

• Explain the mixing of surface and deep ocean waters from thermohaline circulation.

Ocean Currents

• Connection to climate: Warm currents lead to warmer climates; cold currents result in cooler climates.

• Surface ocean currents are responsible for moving warm and cold water globally.

• Driven by:

  • Temperature

  • Gravity

  • Prevailing winds

  • Coriolis effect

  • Locations of continents

Gyres

• Defined as large-scale water circulation patterns.

• Movement patterns:

  • Clockwise in the Northern Hemisphere.

  • Counterclockwise in the Southern Hemisphere.

Surface Ocean Currents

• Influence of air currents: Affects the movement of ocean surface water.

• Key functions: Redistribute heat globally and cause upwelling, bringing nutrients to the surface.

• Five major gyres contain circulation patterns influenced by trade winds and westerlies.

Upwelling

• Definition: Upward movement of ocean water due to diverging currents.

• Impact: Brings nutrients from the ocean bottom, supporting marine populations.

Thermohaline Circulation

• Important for mixing surface and deep ocean waters.

• Driven by salt content and density differences.

• Acts over long time periods, contributing to the Great Ocean Conveyor Belt.

• Mechanism: Sinking of cold, salty water, creating deep ocean currents.

The Great Pacific Garbage Patch

• Importance of oceanic circulation patterns in addressing pollution issues.

Key Points on Thermohaline Circulation

• Moves heat and nutrients across the globe and takes hundreds of years to complete a cycle.

• Density is key: Salt water is denser than freshwater, influencing buoyancy in oceans.

Module 9: The Unequal Heating of Earth

Learning Objectives

• Identify the five layers of the atmosphere.

• Discuss the factors that cause unequal heating of Earth.

• Describe how Earth’s tilt affects seasonal differences in temperatures.

Weather vs Climate

• Weather: Short-term conditions of the atmosphere (e.g., temperature, humidity, clouds, precipitation, wind speed).

• Climate: Average weather in a region over a long period.

• Examples of Weather:

  1. “It’s really hot today!”

  2. “Summer in South Korea is always very humid.”

  3. “Iceland is one of the cloudiest countries in the world!”

  4. “It’s forecasted to rain 20mm tomorrow.”

Earth's Atmosphere

• Composed of 5 layers: Exosphere, Troposphere, Thermosphere, Stratosphere, Mesosphere.

• Troposphere: Closest layer to Earth, extends up to approximately 16 km (10 miles).

• Stratosphere: Above the troposphere, extends from 16 to 50 km (10–31 miles) and contains the ozone layer.

Atmospheric Layers and Temperature

• Temperature decreases with altitude in the troposphere.

• Temperature increases with altitude in the stratosphere due to UV-B and UV-C rays warming the upper part.

• Temperatures in the thermosphere can reach up to 1,750°C (3,182°F).

Solar Energy and Albedo

• Solar energy varies with location due to:

  • The angle at which the Sun's rays strike the Earth.

  • The angle of surface area the rays cover.

  • Different reflectivity of surfaces (albedo).

• Albedo: Percentage of incoming sunlight reflected by a surface; snow and ice have high albedo, while darker surfaces have low albedo.

• Tropical regions near the equator receive more solar energy than mid-latitude and polar regions.

Seasons and Earth's Tilt

• Earth's axis of rotation is tilted at 23.5˚.

• Seasonal changes occur as the Northern and Southern Hemispheres tilt toward and away from the Sun alternately.

• The latitude receiving direct sunlight changes throughout the year, leading to predictable seasons.

Energy Transfer

• Most energy is received at the equator and is transferred globally via currents and atmospheric circulation.