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
- 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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