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.