Energy and Weather Systems Notes

Energy in the Atmosphere

  • Polar Temperature
    • The poles are colder due to indirect solar radiation.
    • Sun’s rays are spread over a larger area at the poles compared to the tropics.

The Sun and Insolation

  • Insolation: Incoming solar radiation (electromagnetic energy from the sun).

Earth's Energy Budget

  • 100% incoming solar energy is distributed as:
    • 6% reflected by atmosphere.
    • 20% reflected by clouds.
    • 4% reflected from Earth's surface.
    • 16% absorbed by atmosphere.
    • 64% absorbed by land and oceans.
    • 3% absorbed by clouds.
    • 15% radiation absorbed by the atmosphere.
    • 23% carried to clouds and atmosphere by latent heat in water vapor.

Factors Influencing Insolation

  1. Tilt of the Earth on its Axis

    • The 23.5-degree tilt leads to seasonal variations in sunlight and temperature.

  2. Angle of Incidence of Sun's Rays

    • Varies by latitude; higher latitudes receive sunlight at shallower angles, spreading energy over larger areas which decreases intensity.
    • Example:
      • At 90° direct rays = high intensity.
      • At lower angles (e.g., 30°) rays are spread out, resulting in lower intensity.

  3. Duration of Day

    • Longer durations of insolation increase temperature.
    • Example: Equatorial regions have approximately 12 hours of sunlight year-round while poles experience greater variation.

  4. Transparency of the Atmosphere

    • Influenced by cloud cover, dust, and water vapor which reflect, absorb, or transmit insolation.
    • A thick cloud layer reduces solar radiation reaching the earth's surface.

  5. Effect of Atmospheric Conditions on Radiation

    • Near-infrared radiation absorption by water vapor and gases.
    • Scattering of light results in visible spectrum color effects including blue skies and red sunsets.

Relationship of Surface Temperature to Insolation

  • Temperature varies throughout the day/year based on insolation intensity and duration.
  • Higher insolation leads to temperature increases when it exceeds energy lost through radiation.

Air Masses

  • Continental Tropical (cT): Originates from land, tropical, dry, and warm.
  • Maritime Tropical (mT): Originates from ocean, tropical, humid, and warm.
  • Continental Polar (cP): Originates from land, high latitudes, dry, and cool.
  • Maritime Polar (mP): Originates from ocean, high latitudes, humid, and cool.
  • Arctic (A): Originates from Arctic, dry, and very cold.

Global Wind Systems

  1. Polar Easterlies: Winds from the east at 60° latitude to the poles.
  2. Prevailing Westerlies: Winds from the west at 30°-60° latitude, responsible for weather movement across the USA.
  3. Trade Winds: Winds from the east between the equator and 30° latitude.

Intertropical Convergence Zone (ITCZ)

  • Area near the equator with converging trade winds, moist air rises creating low pressure, and supporting tropical rainforest moisture.

Doldrums

  • Another term for ITCZ, historically caused ships to become stranded due to low winds.

Horse Latitudes

  • Located around 30° latitude; areas of high pressure causing light winds, named for sailors who jettisoned horses during prolonged trips.

Front Types and Weather Implications

  1. Cold Front: Displaces warm air upward, produces clouds, showers, thunderstorms.
  2. Warm Front: Warm air rises over cold air, characterized by extensive cloudiness and steady precipitation.
  3. Stationary Front: Two air masses resist movement; results in prolonged cloudiness and rain.
  4. Occluded Front: Rapid cold air overtakes warm front; precipitation occurs on both sides.

Pressure Systems

  • High Pressure: Cool, descending air, typically leads to fair weather, marked by a blue ‘H’, rotates clockwise.
  • Low Pressure: Warm air rising, associated with clouds and precipitation, marked by a red ‘L’, rotates counter-clockwise.

Weather Data Gathering Instruments

  1. Thermometers: Measure temperature.
  2. Barometers: Measure air pressure.
  3. Anemometers: Measure wind speed.
  4. Hygrometers: Measure relative humidity.
  5. Ceilometers: Measure cloud height and cover.
  6. Radiosondes: Balloon-borne sensors track atmospheric conditions.
  7. Doppler Radar: Detects precipitation speed/direction aiding in severe weather detection.
  8. Weather Satellites: Monitor cloud patterns and precipitation.

Isobars and Isotherms

  • Isobars: Lines connecting points of equal atmospheric pressure; close together indicate strong winds.
  • Isotherms: Lines of equal temperature, useful in analyzing temperature distributions.

Weather Forecasting Types

  1. Digital Forecast: Uses numerical data for predictions.
  2. Analog Forecast: Compares current conditions to historical patterns; reliability increases in short-term forecasts.