Earth's Energy Balance and Atmosphere Dynamics

Earth's Energy Balance

• Incoming solar radiation is balanced by outgoing radiation from Earth.
• The energy balance is influenced by latitude and seasons.
• Insolation is absorbed by Earth's crust and surface.

Heating The Atmosphere

• Sensible heat transfer warms the air directly through conduction and convection.
• Latent heat transfer occurs when absorbed heat evaporates water, turning it into water vapor, which rises into the atmosphere.
• Outgoing terrestrial radiation is emitted by Earth's surface, warming the atmosphere when absorbed.

Key Words

• Insolation is incoming solar radiation falling on a unit area of Earth’s surface.
• Radiation budget is the balance of energy gain and energy loss.
• Conduction is energy transfer by contact, passing from one molecule to the next.
• Convection is energy transfer by movement of molecules with lots of energy.
• Latent heat is the heat or energy absorbed or released during a phase change of a substance.

Altitude

• Height above sea level, less dense air molecules at higher altitudes, resulting in a natural decrease in temperature.

Aspect

• The angle at which the sun’s rays strike the earth, also known as the angle of incidence.

Latitude

• Distance from the equator.
• Lower latitudes receive more concentrated solar rays, resulting in higher temperatures.
• Higher latitudes receive more dispersed solar rays, resulting in lower temperatures.

Ocean Currents

• Benguela Current (cold) circulates anticlockwise in the Southern Hemisphere.
• Agulhas Current (warm) circulates anticlockwise in the Southern Hemisphere.
• Ocean currents circulate anticlockwise in the southern hemisphere but clockwise in the northern hemisphere.
• Ocean currents influence temperature variations: Coastal areas are maritime with lower temperature ranges, while hinterlands have a continental climate with high temperature ranges.

Latitudinal Influence

• Sun’s radiation hits Earth in parallel waves due to the vast distance between the sun and Earth combined with the sun's immense size.

Latitudinal Factors

• Distance of the atmosphere: Lower latitude regions have shorter distances for insolation to travel resulting in less absorption, reflection, and scattering of energy, while higher latitude regions have longer distances with more energy loss.
• Angle of Incidence: Lower latitudes receive greater angles of incidence with more direct rays, while higher latitudes receive smaller angles of incidence with oblique rays.
• Day and Night: In lower latitudes, there is less annual variation with consistent day and night lengths, while higher latitudes experience greater annual variation and significant changes in daylight and darkness.
• Albedo: Lower latitudes have lower albedo due to vegetation covering the surfaces, absorbing more insolation, while higher latitudes have higher albedo due to white snow and ice, reflecting more insolation.

Key Words

• Albedo is the fraction of insolation reflected from Earth’s surface back into space.
• Insolation angle of incidence is the angle at which the sun’s rays strike the Earth.
• Lower latitudes (0°—30°) receive more concentrated solar rays leading to hotter atmospheric temperatures.
• Higher latitudes (60°—90°) receive dispersed solar rays resulting in cooler atmospheric temperatures.

Earth's Energy Balance

• The balance between incoming solar radiation and outgoing radiation from Earth.
• Depends on latitude and seasons.

Insolation and Earth's Energy Balance

• Insulation is absorbed by Earth's crust and surface.
• Sensible heat transfer: Absorbed heat from the Earth's surface warms the air directly through conduction and convection.
• Latent heat transfer: Absorbed heat is used to evaporate water, turning it into water vapor, which rises into the atmosphere carrying latent heat energy.
• Outgoing terrestrial radiation: Earth's surface emits longwave radiation due to its temperature, which heats the atmosphere when absorbed.

Key Terms

• Insolation: incoming solar radiation falling on a unit area of Earth's surface.
• Radiation Budget: balance of energy gain and energy loss.
• Conduction: energy transfer by contact between molecules.
• Convection: energy transfer by movement of molecules with lots of energy.
• Latent Heat: heat absorbed or released during a phase change of a substance.

Altitude, Latitude, and Aspect Influencing Temperatures

• Altitude: Natural decrease in temperature at higher altitudes due to less dense air molecules.
• Aspect: Sun's rays strike the Earth at different angles, affecting insolation (angle of incidence).
• Latitude: Distance from the equator influences temperature as insolation is received unequally across Earth's surface.

Ocean Currents and Temperature

• Benguela (cold) and Agulhas (warm) currents influence temperature.
• Ocean currents circulate in opposite directions in the Northern and Southern Hemisphere.
• Coastal: Maritime climate with low temperature range due to proximity to the ocean.
• Hinterlands: Continental climate with high temperature range due to distance from the ocean.

Latitudinal Influence

• The sun's radiation hits the Earth in parallel waves due to the vast distance between the Sun and Earth, combined with the immense size of the Sun.
• Factors influencing Latitudinal Temperature Differences:
  • Distance of atmosphere
  • Insolation angle of incidence
  • Length of day and night
  • Albedo of Earth's surface
  • The curvature of Earth.

Albedo

• Albedo: The fraction of insolation reflected back into space from the Earth's surface (1 = high albedo, 0 = low albedo).
• Insolation angle of incidence: Angle at which the sun's rays strike the Earth.

Comparing Lower Latitudes (0°—30°) and Higher Latitudes (60°—90°)

• Lower Latitudes:

  • Distance of Atmosphere: Heat has a shorter distance to travel, less insolation is lost.
  • Angle of Incidence: Receives the greatest angle of incidence, more direct rays.
  • Length of Day and Night: Less annual variation with consistent duration of daylight and darkness.
  • Albedo: Lower albedo, vegetation covered surfaces absorb more insolation.
  • Effect & Result: Concentrated solar rays, absorbed by a smaller surface area, hotter atmospheric temperature, most intense at the Equator.

• Higher Latitudes:

  • Distance of Atmosphere: Heat has a greater distance to travel, more insolation is lost.
  • Angle of Incidence: Receives the smallest angle of incidence, more oblique rays.
  • Length of Day and Night: Greater annual variation with significant changes in duration of daylight and darkness.
  • Albedo: Higher albedo, white snow and ice reflect insolation.
  • Effect & Result: Dispersed solar rays, absorbed by a larger surface area of the Earth, cooler atmospheric temperature, least intense at the poles.