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Unit 3 Water in the Atmosphere

Unit 3 Water in the Atmosphere. Objectives:. Water vapor and the atmosphere How the system works Different ways to measure water vapor What makes it important Humidity, dew point, frost Fog and other clouds Types of precipitation Instruments used to measure moisture.

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Unit 3 Water in the Atmosphere

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  1. Unit 3 Water in the Atmosphere

  2. Objectives: • Water vapor and the atmosphere • How the system works • Different ways to measure water vapor • What makes it important • Humidity, dew point, frost • Fog and other clouds • Types of precipitation • Instruments used to measure moisture

  3. I. Earth’s Hydrologic Cycle • The gigantic system powered by energy from the sun in which the atmosphere that provides a link between the oceans and continents.

  4. Important Components Affecting Weather & Climate • Evaporation – change in state from gas to a liquid. LOTS of energy gained (2260 J/g) • Condensation – change in state from gas to a liquid. LOTS of energy released (latent heat – 2260 J/g) • Transpiration –water vapor released by plants • Precipitation – liquid or solid water that returns back to the Earth’s surface in the form of rain, snow, sleet, or hail.

  5. Distribution of Water on Earth

  6. II. Principles of Air & Water • When liquid water evaporates, it turns into a gas called water vapor. • Amount of water vapor in the atmosphere is limited by temperature: • warmer air holds more water vapor • Saturation: when air can’t hold any more water  Dry skin and chapped lips in the winter

  7. III. Measurement  Impossible to count the number of water vapor molecules in the air! • Dew point: 1. The amount of water vapor in the air 2. Often described as the temperature at which air needs to cool to reach saturation (°F or °C) Table 4-2 Dew Point Threholds Dewpoint temperature ≤ 10°F Significant snowfall is inhibited ≥ 55°F Minimum for severe thunderstorms to form ≥ 65°F Considered humid by most people ≥ 70°F Typical of the rainy tropics ≥ 75°F Considered oppressive by most

  8. Condensation and/or precipitation occurs Dew Point Temperature Saturation occurs

  9. B. Relative Humidity 1. Measure of how close the air is to saturation 2. Saturation occurs at 100% 3. Dependent on temperature and amount of moisture Phoenix, AZ 77°F Lots of water vapor 20% R.H. International Falls, MN 14°F Little water vapor 100% R.H.

  10. Relative Humidity Activityhttp://cimss.ssec.wisc.edu/satmet/modules/clouds/cloudformation_RH.html

  11. Relative Humidity Activity: Answers

  12. IV. Types of Condensation A. Dew - when the air temperature cools beyond the dew point temperature, water is squeezed out of the air (condensation – gas to liquid).  Usually happens in the morning or evening when the temperatures are cooling.

  13. B. Frost - same concept as dew, only with ice crystals instead of liquid water (deposition – gas to solid)  Dew point must be 32°F or less  Water vapor turns to ice

  14. C. Fog - same process as dew forming, but the dew forms on tiny particles in the air that you cannot see Types of fog: 1. Radiation - thin 2. Advection - thick 3. Upslope – mountains 4. Steam – over water 5. Frontal – where precipitation occurs  Need a slight wind to stir particles into air

  15. Radiation fog – Usually forms at night when there are clear skies and fairly high relative humidity (condensation)

  16. Advection fog – warm, moist air moves over a cold surface (condensation)

  17. Upslope fog – air moving up the mountain is forced to cool (condensation)

  18. Steam fog – cool air moves over warm water (evaporation)

  19. Frontal fog – evaporation of rain after cold air moves through

  20. Fun fact: The foggiest location in the U.S. is Cape Disappointment, WA

  21. V. Formation of Clouds A. Clouds are composed of tiny particles of liquid water and ice crystals B. They form when air cools to the dew point temperature, and relative humidity increases to 100%. Eventually the excess water is dumped and latent heat is released. 100% R.H. D.P. Temp Clouds form Growth of precip. begins Decrease temperature

  22. C. Condenstion nuclei – particles in which water vapor molecules can attach to D. Four ways to form clouds by lifting air: 1. Orographic lifting 2. Frontal wedging 3. Convergence 4. Convection dust c c c salt c pollen

  23. Orographic Lifting– air that is forced to rise over a mountain range

  24. Frontal wedging – warmer air moving over a cold pocket of air

  25. Convergence - winds blowing in different directions forces air up

  26. Convection – warm parcels of air rise due to solar heating

  27. VI. Types of Clouds A. Basic Cloud Types: 1. Cirrus – high, wispy 2. Alto – middle 3. Stratus – low, layers 4. Cumulus – cotton-like 5. Nimbus – produce rain

  28. B. Special clouds: 1. Lenticular– formed in mountainous areas

  29. 2. Contrails– forms when the humidity starts to increase (bad weather is approaching!)

  30. 10,000 km 3,000 km Fun fact: An average sized cloud contains 13 million gallons of water- enough to fill a small pond!

  31. VII. Types of Precipitation A. Rain - spherical liquid droplets

  32. B. Snow – aggregates of ice crystals

  33.  Ice crystals shapes are based on temperature in which they form

  34. Fun fact: Powdery snow is the result of very low temperatures because the moisture content of air is small.

  35. C. Sleet – frozen raindrops

  36. D. Glaze – rain that freezes when it comes in contact with the ground

  37. Fun fact: The snowiest city in the U.S. is Rochester, NY (avg. of 239 cm per year). Buffalo, NY is a close runner-up.

  38. E. Hail – small to large chunks of ice that are composed of several layers

  39. Fun fact: Largest hailstone ever recorded fell in Aurora, Nebraska in June 2003. It measured 17.8 cm in diameter and weighed 1.5 pounds!

  40. Another fun fact: People used to believe that strong noises- explosions, cannon shots, or ringing church bells- prevented hail formation.

  41. Height Values: 1000mb: 246m 850mb: 1490m 700mb: 3013m 500mb: 5590m X = Probable location of cloud formation (dew point = air temperature) Temperature curves are below freezing X ALL SNOW

  42. Height Values: 1000mb: 189m 850mb: 1514m 700mb: 3098m 500mb: 5730m X = Probable location of cloud formation (dew point = air temperature) Snow X Rain FREEZING RAIN Shallow freezing layer

  43. Height Values: 1000mb: 205m 850mb: 1481m 700mb: 3057m 500mb: 5660m X = Probable location of cloud formation (dew point = air temperature) Snow ? X Rain Deep freezing layer SLEET

  44. Height Values: 1000mb: 156m 850mb: 1525m 700mb: 3128m 500mb: 5790m X = Probable location of cloud formation (dew point = air temperature) X ALL RAIN

  45. In case you wanted to know…

  46. VIII. Precipitation Measurement A. Rain gauge: measures rainfall by funneling liquid into a cylinder or bucket below.

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