GEOG 203: Planet Earth - Atmospheric Energy and Global Temperatures

Atmospheric Energy and Global Temperatures

Energy Essentials

• Insolation: Incoming solar radiation, includes both direct and diffuse radiation received at Earth's surface.

• Pathways: Different ways energy moves through the atmosphere and affects Earth.

• Balance: The equilibrium between incoming and outgoing energy.

Earth–Atmosphere Radiation Balance

• Greenhouse Effect: The process by which certain gases trap heat in the atmosphere.

Surface Radiation Balance

• Net Radiation: Difference between incoming and outgoing radiation.

• Sensible & Latent Heat: Types of heat transfer used in temperature regulation on Earth's surface.

Temperature

• Principal Controls: Factors affecting temperature such as latitude, altitude, cloud cover.

• Earth’s Patterns: General temperature distributions globally.

Atmospheric Energy Balances

• The sun provides solar energy to heat Earth’s surface and atmosphere.

• Distribution of Energy: Energy is unevenly distributed across time and space.

• Transmission of Energy: Refers to all radiation that passes through the atmosphere, consisting of:

  • Shortwave radiation: Incoming solar energy (direct and diffuse).

  • Longwave radiation: Outgoing radiation from Earth.

Energy Pathways

• Energy paths include:

  • Reflection: Energy reflected back into space.

  • Scattering: Changes the direction of light without changing wavelength, resulting in diffuse radiation; 7% of insolation is scattered back to space.

  • Refraction: The change in direction and speed of radiation transitioning between media (e.g., space to the atmosphere) adds approximately 8 minutes of sunlight to each day.

  • Reflection: Defined as the bouncing back of energy with unchanged properties (brightness termed Albedo).

Albedo Metrics

• Albedo: Percentage of reflected insolation.

  • 0% Albedo: No reflection (dark surfaces).

  • 100% Albedo: Total reflection (light surfaces).

  • Specific Albedo Values:

  • Fresh snow: 80%-95%

  • Grass: 25%-30%

  • Asphalt: 5%-10%

  • Earth's average: 31%

  • Water bodies: 10%-60% (varies with sunlight angle).

Absorption of Radiation

• Absorption: Assimilation of radiation by an object, converting energy forms.

• Energy Distribution:

  • 69% of insolation is absorbed:

  • 45% by Earth's surface (land and oceans)

  • 24% absorbed by the atmosphere (gases, dust, clouds).

Mechanisms of Heat Transfer

• Conduction: Molecule-to-molecule transfer of heat.

• Convection/Advection: Vertical or horizontal heating transfers through movement.

Energy Balance at Earth’s Surface

• Energy Gains:

  • Diffuse: 20

  • Direct: 25

  • Infrared: 96

• Total Gains = 141

• Energy Losses:

  • Latent: 19

  • Sensible: 4

  • Infrared: 110

  • Total Losses = 141

• Conclusion: Surface energy budget is balanced.

Earth-Atmosphere Energy Balance Breakdown

• Shortwave Portion:

  • Total solar energy input: 100

  • Earth's Albedo: -31

  • Atmospheric losses: Various values for reflected, absorbed, and diffused radiation.

• Longwave Portion:

  • Energy radiated back to space: -69

  • Overall energy losses and gains are monitored, providing insights into temperature dynamics and the greenhouse effect.

The Greenhouse Effect

• Discovered by Eunice Foote.

• Outgoing longwave radiation absorbed by greenhouse gases (e.g., water vapor, CO2, methane).

• Impact of Clouds: Different cloud types affect temperature:

  • High clouds trap heat (warming effect).

  • Low clouds reflect sunlight (cooling effect).

Daily Radiation Curves

• Insolation Peaks: Highest amount of solar radiation received at noon.

• Temperature Lag: Highest temperatures are typically observed mid-afternoon (around 3 PM). Coldest periods occur just after sunrise.

Metabolic Heat at Earth’s Surface

• Net radiation calculation:
  $\text{Net Radiation} = +SW<em>{in} - SW</em>{out} + LW<em>{in} - LW</em>{out}$

• Components of net radiation include latent heating, sensible heating, and ground heating/cooling, balanced annually.

Global Temperature Measurement

• Different temperature scales:

  • Celsius (°C), Fahrenheit (°F), and Kelvin (K).

• Significant Temperatures:

  • Boiling Point: 100°C = 212°F

  • Melting Point: 0°C = 32°F.

• World Records:

  • Highest Recorded Temperature: 57°C in Death Valley.

  • Lowest Recorded Temperature: -89°C in Vostok, Antarctica.

Principal Temperature Controls

1. Latitude: Affects both insolation and temperature.

2. Altitude: Temperature decreases with altitude (approx. -6.4°C per 1000 m).

3. Cloud Cover: Influences daily temperature variation.

4. Land-Water Differences: Variations in heat retention and transfer.

Effects of Clouds on Temperature

• Clouds can moderate temperatures:

  • During night: Insulate, increasing minimum temperatures.

  • During day: Reflect, decreasing maximum temperatures.

Land-Water Heating Differences

• Land vs. Water:

  • Land: Rapid heating/cooling, leading to extreme temperature variations.

  • Water: Slow heating/cooling, leading to milder conditions.

• Maritime Influence: Locations near oceans experience milder climates compared to those inland.

Comparisons of Cities

• Vancouver vs. Winnipeg: Different annual temperature ranges due to Maritime vs. Continental climates.

• San Francisco vs. Wichita: Illustrates the differences in temperature ranges driven by coastal proximity versus continental positioning.

Air Temperature and Human Perception

• Wind chill: Affects how temperature is perceived under cold and windy conditions.

• Heat index: Reflects perceived temperature based on humidity and heat.

Wind Chill Table

• Demonstrates effects of temperature and wind speed on perceived coldness, indicating the temperature at which frostbite risks increase significantly.

Heat Index Table

• Evaluates how temperature and humidity combine to affect perceived temperature and potential risks of heat disorders.

• Important Measures:

  • Likelihood of experiencing heat cramps, exhaustion, and stroke at specific temperature and humidity levels.