Earth's Atmosphere & Weather Notes

Earth's Movement

  • Earth rotates on its axis daily, causing the sun's perceived movement.
  • Earth revolves around the sun annually due to gravitational forces.

Latitude and Sunlight

  • Different latitudes receive varying sunlight amounts.
  • Equator: more direct sunlight, warmer.
  • Poles: less direct sunlight, colder.
  • Climate depends on the balance of incoming vs. outgoing radiation.

Seasons: Axial Tilt

  • Earth's axis is tilted at 23.5 degrees.
  • This tilt causes changing orientations relative to the sun during orbit, resulting in seasons.

Solstices

  • Summer & Winter Solstices: sun directly overhead at latitude 23.5 degrees North or South.
  • Marks the "longest" and "shortest" days of the year

Equinoxes

  • Occur halfway between solstices, marking spring and autumn.
  • Neither hemisphere tilts towards the sun, resulting in equal day and night lengths.

Weather vs. Climate

  • Weather: short-term atmospheric conditions (temperature, precipitation, etc.).
  • Climate: long-term weather patterns based on latitude, altitude, proximity to water, etc.
  • Climate changes over long periods (~30 years).

Air Pressure

  • Measurement of air force on a square meter of land.
  • Lower altitude = higher pressure; higher altitude = lower pressure.
  • Hot air rises (lower pressure); cold air sinks (higher pressure).

Circulation

  • Convection: hot air rises, cold air sinks.
  • Coriolis Effect: Earth's rotation affects air patterns.

Water Cycle

  • Driven by insolation.
  • Evapotranspiration: evaporation from land and transpiration from plants.
  • Advection: water movement in the atmosphere.
  • Condensation: cloud formation.
  • Precipitation: water falling from clouds.

Köppen Climate Classification

  • Divides climates into 5 groups based on temperature and vegetation.

Milankovitch Cycles

  • Long-term changes affecting global warming/cooling.
    • Eccentricity: Earth's orbit shape (100,000-year cycle).
    • Obliquity: Axis tilt (41,000-year cycle).
    • Precession: Wobble of Earth's axis (24,000-year cycle).

Other Climate Factors

  • Solar output changes (11-year cycle).
  • Plate tectonics: ocean/current changes.

Greenhouse Effect

  • Atmospheric gases absorb heat, preventing it from leaving, specifically infrared radiation.
  • Main gases: carbon dioxide, methane, water vapor.
  • Keeps climate warm but can cause global warming with excessive gases.

Climate History

  • Paleodata: isotopes indicate past temperatures.
  • Tree rings: reveal historical climate conditions.
  • Ice cores: preserve past atmospheric conditions and temperatures, isotope ratios of oxygen.

Current Climate

  • Earth is in an ice age with alternating glacial and interglacial periods.
  • Interglacial began ~11,000 years ago.