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The Atmosphere

The Atmosphere. Chapter 11. Atmospheric basics. Atmospheric composition Permanent gases 99% Nitrogen and Oxygen 1% CO 2 Argon and H 2 O Variable gases Water vapor and Ozone vary place to place Atmospheric particles Dust, salt and ice. Atmospheric Layers. Troposphere Closest to Earth

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The Atmosphere

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  1. The Atmosphere Chapter 11

  2. Atmospheric basics • Atmospheric composition • Permanent gases • 99% Nitrogen and Oxygen • 1% CO2 Argon and H2O • Variable gases • Water vapor and Ozone vary place to place • Atmospheric particles • Dust, salt and ice

  3. Atmospheric Layers • Troposphere • Closest to Earth • Where weather is found • Temp and altitude are inversely related • Stratosphere • Temp and altitude are directly related • Contains the ozone layer • Source of heat • Absorbs UV radiation

  4. Mesosphere • Temp and altitude are inversely related • Little UV is absorbed here • Thermosphere • Temp and altitude are directly related • Due to lack of density of particles • Contains the ionosphere • Exosphere • Outermost layer • No definitive outer layer

  5. Energy Transfer in the Atmosphere • Radiation • Transfer of thermal energy by electromagnetic waves • Touching does NOT happen • Conduction • Transfer of thermal energy when particles collide • Touch is REQUIRED • Convection • Transfer of thermal energy as heated fluids move • Has to be in a FLUID

  6. Properties of the Atmosphere • Temperature • Measured in Celsius or Fahrenheit here in US • Air pressure • This is the downward force of the air molecules above you in the atmosphere • Measured in millibars (.8mmHg or .03 in Hg) • Density • The amount of molecules in the air per unit of volume • Measured in kg/m3

  7. Pressure-temperature-density relationships • Pressure and temperature • At the same density, The greater the temperature, the greater the pressure • Pressure and density • At the same temperature, the greater the pressure the greater the density • Temperature and density • At the same pressure, the greater the temperature, the less the density

  8. Temperature inversion • This is an increase in temperature with elevation in the troposphere • 1 possibility is rapid cooling of surface temperature – cold, clear, still winter night • This can negate the radiation of heat from the surface leaving the surface colder than the air above it. • Can lead to a hazy or dense foggy conditions • Pollutants can be trapped in this situation because it can’t escape the cold air

  9. Wind • Pressure difference is the primary factor in wind movement • Wind moves from areas of higher pressure to areas of lower pressure • Temperature affects the density of the air and hence the pressure • Wind speed changes in the upper atmosphere • It speeds up because of lack of friction

  10. Humidity • Saturation occurs when the amount of water vapor in the air is “maxed out” • Relative humidity is how much water is in the air vs. how much it can hold • Dew point is the temperature air must be cooled to reach saturation • Latent heat is the extra energy water vapor has that liquid water doesn’t have – change of state

  11. Clouds and precipitation • Cloud formation • Clouds form when rising air carrying water vapor cools • a condensation nucleus is required for the cloud to form. • When there are enough droplets formed around the nucleus to be visible… a cloud is formed • Stable Air • Air is stable when it rises based on its thermal energy, then settles back into a position • This determines the type of cloud formation present • Unstable Air • Air that is surrounded by a cooler air – this forms thunder storm clouds

  12. Atmospheric lifting • Orographic lifting occure when clouds lift over topography – a mountain • Convergence • This is where clouds approach from opposite directions. • Uplift occurs based on the temperatures of the air masses

  13. Types of Clouds • Low clouds • Cumulus • Stratus • Middle clouds • Altocumulus • Altostratus • High clouds • Cirrus • Unstable air gives clouds a vertical build

  14. Precipitation • Any water that falls from the sky • Water droplets must increase in size significantly in order to fall • Coalescence is one way this happens

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