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The Atmosphere

The Atmosphere. Basic Structure. Composition. Combination of many gases Nitrogen - 78% Oxygen – 21% Water Vapor – 0% to 4% Argon – 0.93% Carbon Dioxide – 0.03% Neon, Helium, Methane, Krypton, – 0.01% Hydrogen, Oxone , Xenon. Key Atmospheric Gases.

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The Atmosphere

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  1. The Atmosphere Basic Structure

  2. Composition • Combination of many gases • Nitrogen - 78% • Oxygen – 21% • Water Vapor – 0% to 4% • Argon – 0.93% • Carbon Dioxide – 0.03% • Neon, Helium, Methane, Krypton, – 0.01% Hydrogen, Oxone, Xenon

  3. Key Atmospheric Gases • Amount of nitrogen and oxygen are critical • Any significant change would end life on Earth • Water vapor • Helps with energy regulation • Exists as solid, liquid and gas • Carbon dioxide • Helps with energy regulation • Ozone • Ultraviolet (UV) radiation shield

  4. Atmospheric Structure • Lower Atmospheric Layers • Troposphere • Closest to Earth’s surface • Holds most of the atmosphere’s mass • Most weather occurs here • Gets colder as you get higher • From 9km (poles) to 16km (tropics) high • Stratosphere • Mostly made of ozone (O3) • Gets warmer as you get higher • Top of layer is about 50km above the Earth’s surface

  5. Atmospheric Structure • Upper Atmospheric Layers • Mesosphere • Gets colder as you get higher • Top of the layer is around 100km above Earth’s surface • Thermosphere • Holds a small part of the atmosphere’s mass • Gets warmer as you go higher (can exceed 1000oC) • Top layer is around 500km above Earth’s surface • Ionosphere – contains electrically charged particles • Exosphere • Outer most layer of Earth’s atmosphere • Contains light gases Hydrogen (H) & Helium (He)

  6. Solar Fundamentals • The sun is the source of all energy in the atmosphere • Sun’s energy is transferred in 3 ways: • Radiation – through visible light, ultraviolet (UV) radiation & other forms of electromagnetic waves • Conduction – passed from one molecule to the next; must be touching • Convection – flow of a heated substance

  7. Diagrams • Structure of the Atmosphere • pg. 273 • Solar Radiation • pg.275 • Energy in Earth’s Atmosphere • pg. 276

  8. State of the Atmosphere Temperature and Pressure

  9. Temperature or Heat • Temperature • How fast or slow molecules move around • More molecules = higher temperature • Faster moving molecules = higher temperature • Heat • Transfer of energy between substances • Flows from warmer to cooler • Fuels atmospheric processes

  10. Measuring Temperature • Fahrenheit (oF) • Water boils at 212oF Water freezes at 32oF • Absolute Zero at -523oF • Celsius (oC) • Water boils at 100oC Water freezes at 0oC • Absolute Zero at -273oC • Kelvin (K) • Water boils at 373 K Water freezes at 273 K • Absolute Zero at 0K

  11. Atmospheric Temperature Changes • Dew Point • Temperature that air must cool to at constant pressure to reach saturation • Saturation is when air is holding as much water as possible • Air must be saturated for condensation to occur • Lifted Condensation Level (LCL) • Height at which air has cooled enough for condensation to occur • Point at which clouds form

  12. Air Pressure and Density • Air is denser and has higher pressure closer to the Earth’s surface • Temperature – Pressure – Density Relationship • T P • T P Temperature Inversion - a pocket of warmer air in between cooler air • T D • T D

  13. Wind • Cool air sinks because it is more dense • Forces warm, less dense air upwards • Wind moves from areas of high pressure to areas of low pressure • High and low pressure areas form due to uneven heating of Earth’s surface

  14. Relative Humidity • Amount of water vapor in a volume of air relative to how much water vapor the volume of air can hold • Warm air can hold more water vapor • Expressed as a percent

  15. Moisture in the Atmosphere Clouds

  16. Cloud Formation • Warm, less-dense air rises, expands and cools in a convection current • As the air reaches its dew point, water vapor condenses around condensation nuclei (sea salt, dust) • Can also form from orographic lifting • Wind encounters a mountain and is forced up • Collision of air masses of different temperatures

  17. Stability and Latent Heat • Stability – when an air mass resists rising • Can become unstable if the air is cooler than the surface beneath it • Latent heat – energy stored in water vapor • Released as water vapor condenses • Warms the atmosphere • This can give energy to a storm and make it more intense

  18. Types of Clouds HEIGHTSHAPE Cirro –above 6000m Cirrus – wispy, stringy Cummulus – puffy, Alto – 2000-6000m lumpy looking Stratus - featureless Strato – below 2000m sheets Nimbus – low, grey Fog – on the groundrain clouds

  19. Low Clouds • Form from intense heating • Summer sun shining on dark fields • Air expands and rises, then begins to cool • At LCL condensation occurs and a cloud forms • If the cloud stay warmer than the surrounding air it will continue to grow • If not it will flatten and be spread out by wind • stratocumulus, layered cumulus, stratus

  20. Middle Clouds • Altocumulus, altostratus • Can be a mix of liquid water and ice crystals • Usually layered

  21. High Clouds • Cirrus, cirrostratus • Made of ice crystals • Indistinct, continuous layer that sometimes covers the sky

  22. Vertical Development Clouds • A cumulus cloud that starts as a low cloud and continues to grow through the middle heights and beyond • Becomes a huge cumulonimbus cloud with an anvil shaped top • Produce thunderstorms with torrential rains and high winds

  23. Precipitation • Coalescence – when water droplets collide and make a bigger droplet • Primary force in warm clouds • Four main types are rain, sleet, snow, hail

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