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Weather and Climate

Weather and Climate . “Climate is what you expect. Weather is what you get.” –Mark Twain. Water is also present in varying amounts up to 4.0%. Structure of the atmosphere . Air Pressure and Density. Why do you need an oxygen mask to climb to the Summit of Mt. Everest?.

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Weather and Climate

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  1. Weather and Climate “Climate is what you expect. Weather is what you get.” –Mark Twain

  2. Water is also present in varying amounts up to 4.0%

  3. Structure of the atmosphere

  4. Air Pressure and Density • Why do you need an oxygen mask to climb to the Summit of Mt. Everest?

  5. Transfer of Energy through Radiation Radiation defined: • the transfer of E through space by electromagnetic waves (visible light and other forms). • All substances with a temperature above absolute zero emit radiation. Higher temperature substances emit shorter wavelengths.

  6. Electromagnetic spectrum

  7. Solar radiation is absorbed or reflected • Each year, Earth reflects about as much energy as it receives from the Sun. • Rate of absorption depends on surface: water heats up and cools down more slowly than land; dark objects absorb energy faster than light ones.

  8. Solar radiation does not heat air directly • Heat reflected off the Earth is absorbed by the atmosphere, which warms air through conduction and convection. • Conduction is the transfer of heat when molecules collide- this heats the surface of the Earth. • Convection currents are generated by the flow of heated air; warm air rises, expands and cools, then starts to sink and begins the process again.

  9. Convection currents

  10. Convection currents

  11. Atmospheric properties

  12. Temperature vs. Heat • Temperature measures how quickly or slowly molecules move around. • More molecules or faster-moving molecules yield a higher temperature • Heatis the transfer of Energy that occurs because of a difference in temperature between substances. • Heat flows from higher temperature objects to lower temperature objects

  13. Key Point: • Heat is the transfer of energy that fuels atmospheric processes. • Temperature is used to measure and interpret that energy.

  14. Absolute Zero • The temperature at which there is no molecular movement. • Measured on the Kelvin scale, the SI Unit of Temperature.

  15. Dew Point • The temperature to which air must be cooled at constant pressure to reach saturation. • Saturation is the point at which air holds as much water vapor as it possibly can. • Condensation can’t occur without saturation. • Condensation occurs when water vapor turns to liquid water.

  16. Wind Cool, more dense air, sinks and forces warmer, less dense air, upwards. Because of unequal heating of the Earth, density imbalances form, creating areas of high and low pressure and driving wind. Wind is air moving from areas of high pressure to areas of low pressure.

  17. Relative Humidity Measure the ratio of Water vapor in a volume of air How much water vapor that air is capable of holding Warm air can “hold” more moisture than cold air. Faster molecules are more likely to hold water vapor because they are moving too rapidly to condense.

  18. Relative Humidity

  19. Cloud Formation • Warm air rises, expands, cools, and condenses around condensation nuclei (small particles in atmosphere like dust, sea salt, etc.). Condensation occurs at the Lifted Condensation Level. • Warm air can rise as a result of: • Convection currents • Orographic lifting (encountering mountains and rising, expanding, and cooling) • When two air masses of different temperatures meet

  20. A rising air mass cools at 10°C/1000m. Eventually, it reaches its condensation temperature. The height at which condensation occurs is called the lifted condensation level.

  21. Adiabatic Lapse RatesDry air cools more rapidly than saturated air

  22. Orographic lifting

  23. Colliding air masses

  24. How clouds form

  25. Types of clouds

  26. Clouds form at different altitudes • Low clouds form as moist air rises, cools, and expands, reaching its Lifted Condensation Level, and condenses. If it stays warmer than the surrounding air, it will continue to grow. If it does not stay warmer, the wind will blow it horizontally into stratus, stratocumulus or cumulus clouds.

  27. Stratus clouds

  28. Cumulus clouds

  29. Middle Clouds • Form between 2000-6000m • Can be either all liquid or a mix of liquid and ice crystals • Usually layered • Altocumulus clouds (resemble white fish scales) • Altostratus clouds (dark, thin veils that sometimes produce light precipitation)

  30. Altocumulus

  31. Altostratus

  32. High clouds • Air mass has been warmer than surrounding air so has continued to rise to heights greater than 6000m • Clouds are made of ice crystals • Cirrus clouds (thin and wispy) • Cirrostratus clouds (a continuous cloud cover that varies in thickness; can be thick enough to block out the Sun or Moon)

  33. Cirrus Clouds

  34. Cirrostratus clouds

  35. Clouds of vertical development • If air in a cumulus cloud is unstable enough, it will be warmer than surrounding air and continue to grow and expand upward. • As it rises, water vapor continues to condense, and the air receives additional warmth from the release of latent heat. • These clouds can get very big, up to 18,000m tall. Tops are made of ice crystals. Anvil shape develops

  36. Cumulonimbus clouds

  37. Spot the cumulonimbus

  38. Natural Influences on ClimateHow many can you think of? • Latitude • Seasonal influences • Hadley Cells • Urban Heat Islands • El Nino • Volcanic Activity • Solar Activity • Earth’s Orbit • Earth’s Axis • Earth’s Wobble

  39. Solar Activity • Sunspot activity occurs in cycles, every 11 years. • Increased solar activity coincides with warmer-than-normal climates • Periods of low solar activity coincide with colder-than-normal climates • The Maunder minimum, a period with no sunspot activity (1645-1716), coincided with a very cold climatic period called the “Little Ice Age.”

  40. Maunder Minimum

  41. Variation in Earth’s Orbit (Eccentricity)

  42. Variation in the tilt of Earth’s Axis (Obliquity)occurs every 41,000 years (now at 23.5°)

  43. Variation in Earth’s wobble (precession) occurs every 26,000 years. We will point toward Vega by year 14000.

  44. Variations in Earth’s obliquity, eccentricity, and precession are termed Milankovitch Cycles

  45. Review of Major Air Pollutants (except carbon dioxide)

  46. Legislation addresses pollution • Air Pollution Control Act (1963) funded research and encouraged emissions standards • The Clean Air Act of 1970 • Set standards for air quality, limits on emissions • Provided funds for pollution-control research • Allowed citizens to sue parties violating the standards • The Clean Air Act of 1990 strengthened regulations for auto emissions, toxic air pollutants, acidic deposition, stratospheric ozone depletion • Introduced emissions trading for sulfur dioxide

  47. The EPA sets standards • The EPA sets nationwide standards for emissions and concentrations of toxic pollutants • States monitor air quality • They develop, implement, and enforce regulations • They submit plans to the EPA for approval • The EPA takes over enforcement if plans are inadequate • Criteria pollutants = pollutants that pose especially great threats to human health • Carbon monoxide, sulfur dioxide, nitrogen dioxide, tropospheric ozone, particulate matter, lead

  48. We have reduced air pollution • Total emissions of the six monitored pollutants have declined 60% since the Clean Air Act of 1970 • Despite increased population, energy consumption, miles traveled, and gross domestic product

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