Chapter 2 - The Atmosphere

Composition

  • Nitrogen - 78%
    • Fundamental for living organisms. Deposits through nitrogen fixation and reaction involving lightning and subsequent precipitins.
  • Oxygen - 21%
    • Produced through photosynthesis
  • Water Vapor - 0-4%
    • Large amounts near the equator, areas with low atmospheric water vapor are over deserts and polar areas.
  • Carbon Dioxide - <<1%
    • Produced during cellular respiration, combustion of fossil fuels, and decay of organic matter. Required for photosynthesis.
  • Methane - <<<1%
    • Contributes to the greenhouse effect.
  • Nitrous Oxide - <<<1%
    • Contributor to the greenhouse effect. Single most important contributing substance reducing stratospheric ozone.
  • Ozone - <<<1%’
    • Most found in the stratosphere. Absorbs UV Radiation.

Structure

  • The atmosphere is split up into multiple layers.
  • Troposphere
    • Weather occurs in this zone.
    • 75% of atmospheric mass is in this zone.
  • Stratosphere
    • Temperature increases because of the UV radiation in this zone.
  • Mesosphere
    • Coldest layer.
    • Ice Clouds occur here.
  • Thermosphere
    • Molecules are converted into ions.
    • Gamma Rays, X-Rays, UV radiation make the temperature rise.

Weather and Climate

  • Weather
    • Caused by the movement or transfer of heat which causes unequal heating of the earth’s surface.
  • Climate
    • Describes the total of all weather occurring over a period of years.
  • Radiation
    • The flow of electromagnetic radiation. It is how the Earth receives solar energy.
  • Conduction
    • Transfer of heat through solid substances.
    • Causes a difference in temperature between different parts of the substance.
  • Convection
    • The movement of warmer molecules in the air.
    • Primary way energy is transferred from hotter to colder regions in the Earth’s atmosphere. Determines weather patterns.
  • Factors that influence the climate
    • Air Mass
    • Albedo (Reflectivity)
    • Altitude
    • Angle of Sunlight
    • Carbon Cycle
    • Clouds
    • Distance to Ocean
    • Fronts
    • Greenhouse Effect
    • Human Activity
    • Land Changes
    • Landmass Distribution
    • Latitude
    • Location
    • Mountain Ranges
    • Pollution
    • Precession
    • Rotation
    • Solar Output
    • Volcanoes
    • Wind Patterns

Atmospheric Circulation - Pressure

  • Air closest to the Earth’s surface is warmer and rises.
  • Air higher up in the atmosphere is colder and will sink.
  • Low-Pressure System
    • Low Pressure at the center.
    • Winds blow towards the low pressure.
    • Usually forms clouds and precipitation.
    • Produces cloudy and stormy weather.
  • High-Pressure System
    • Wind blows away from the high pressure.
    • Contain cool, dense air.
    • Usually associated with fair weather.
  • Coriolis Effect
    • Earth’s rotation on an axis causes winds to not travel straight.
  • Hadley, Ferrel, and Polar Cells
    • The worldwide system of winds.
  • Hadley Air Circulation Cells
    • Air heated near the equator rises and spreads out north and south.
    • After cooling in the upper atmosphere, the air sinks back down to the subtropical climate zone.
  • Ferrel Air Circulation Cells
    • Develop between 30 degrees and 60 degrees north and south latitudes.
    • Area where these circulation cells control contains broadleaf, deciduous, and coniferous evergreen forests.
  • Polar Air Circulation Cells
    • Icy-cold, dry, dense air that descends from the troposphere to the ground.
    • Air meets with warm tropical air and then returns to the poles.
    • Reason why polar areas are deserts.
  • Polar Vortex
    • Low-Pressure zone that lies above both poles.
    • Large Mass of Cold Air.

Hurricanes, Tornadoes, and Cyclones

  • Hurricanes
    • Most severe weather phenomenon on the planet.
    • Warm areas over oceans where the trade winds converge.
    • Separate thunderstorms move in a circular motion. It allows them to pick up moisture and heat energy from the ocean.
    • Energy from the hurricane dissipates over land.
  • Tornadoes
    • Swirling masses of air.
  • Tornadoes vs Cyclones
    • Tornadoes are caused by a singular storm.
    • Cyclones are developed from multiple separate storms.
    • Tornadoes are over land.
    • Tropical Cyclones die out over land due to the lack of moisture.
  • Monsoons
    • Strong, violent winds that change direction with the season.
    • Blows from cold to warm regions.

El Niño - Southern Oscillation

  • La Nina
    • Normal Conditions
    • Easterly Trade Winds move water and air warmed by the sun towards the west.
    • Water in the Pacific is 14 degrees hotter.
  • El Nino (Warm Phase)
    • Air pressure reverses direction.
    • Causes extensive fish kills due to water moving away.
    • Ocean temperatures are their warmest.
    • Enhances convection.
  • El Nino (December - February)
    • Surface water returns to cooler, nutrient-rich water.
    • Supplies necessary nutrients to phytoplankton.
  • La Nina (Cold Phase)
    • Trade winds that blow west are stronger than usual.
    • Leads to wetter than normal conditions across the Pacific Northwest, and drier weather in the Southern United States.
    • Winter temperatures are warmer in the Southern United States and cooler in the northwest.
    • Causes heavier monsoons in Southeast Asia and India.

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