1. Water in the Atmosphere Earth Science/Geology Mr. Traeger

2. We must understand the properties of water in order to understand how it behaves in the atmosphere. The structure of water looks like “Mickey Mouse.” Two Hydrogens and One Oxygen bond to make H 2 O.

3. We must understand the properties of water in order to understand how it behaves in the atmosphere. Water molecules bond in hydrogen bonding where the positive hydrogen bonds with the negative oxygen.

4. This bonding of molecules allows for changes of state of water. Water molecules bond in hydrogen bonding where the positive hydrogen bonds with the negative oxygen.

5. Water is the only substance that commonly exists in all three states of matter. This is solid, liquid, and gas (Spaulding, 390).

6. Here are the states of water. See page 391 in your book for a better diagram. Note where heat is released and where heat is absorbed.

7. Remember when we heated water from ice to water to steam? This is the graph that we did in class.

8. Notice how water goes through phase changes from solid (ice) to liquid (water) to gas (water vapor).

9. Water melts at zero degrees Celsius and boils at 100 degrees Celsius.

10. The change of state of water contributes to the Water Cycle, the unending circulation of water throughout the planet. See page 13 in your book for more details. Water CycleWater Cycle

11. Humidity The City of Atlanta, Georgia has very high humidity in the summertime! What does it feel like when it is hot and humid?

12. What is Specific Humidity?

13. Specific Humidity is the actual amount of water vapor in the air. It does not depend on temperature. It is expressed in grams of water per kilograms of air.

14. What is Relative Humidity?

15. Relative Humidity is the actual amount of water vapor in the air compared to the maximum amount of water vapor the air can hold.

16. Relative humidity is expressed in percentage.

17. If the air has a specific humidity of 50 g/kg and the air will hold 100 g/kg, what is the relative humidity?

18. 50 / 100 = 0.5 0.5 X 100 = 50 So the relative humidity is 50%.

19. If the air has a relative humidity of 100%, what will happen?

20. Clouds or fog will form!

21. Go here to see the different types of clouds. Go here to see even more clouds! here

22. Multiple cloud layers as seen from the air climbing out of Minneapolis, MN on 12/31/05. Stratus clouds below and cirrostratus/cirrocumulus clouds above

23. Clouds or fog will form when the temperature and dew point are the same.

24. But in order for clouds or fog to form, small dust particles called condensation nuclei are required!

25. Fog is a cloud at or near the ground.

26. Radiation fog is formed when moist air near the ground is cooled to dew point on a cold, clear night.

27. Advection fog is formed when warm, moist air moves over a cold ocean surface. The fog off of our coast is advection fog.

28. Cloud Formation A cloud will form at the elevation where the temperature and dew point are the same.

29. Cloud Stability Flat clouds like stratus clouds are stable. This means that the center of the cloud is colder or at the same temperature as outside.

30. Cloud Stability Clouds with vertical growth are said to be unstable, which means the center of the cloud is warmer than the air outside. Warm air will rise.

31. Cloud Stability Instability in a cumulonimbus cloud leads to thunderstorms, lightning, hail, flooding, wind, and tornadoes. thunderstormslightninghailfloodingwind tornadoes thunderstormslightninghailfloodingwind tornadoes

32. Lapse rates A lapse rate is how fast air cools with altitude. You can use this value to calculate the altitude at which a cloud will form.

33. Lapse rates Dry air cools at a rate of around 10°C per every 1000 meters.

34. Lapse rates Moist air cools at an average of 7°C per every 1000 meters.

35. Cloud formation A cloud will form when the temperature and dew point temperature are the same. See an animation of cloud formation. animation

36. Cloud formation problem #1 The temperature at the surface is 20°C and the dew point is 10°C. Assuming that the dew point temperature does not decrease (which it does), what altitude will the cloud form at? Assume that there is dry air between the surface and the cloud.

37. Cloud formation problem #1 Answer 20° -10° = 10° Dry air cools 10° C for every 1000 meters. So, the cloud will form at 1000 meters!

38. Cloud formation problem #2 The temperature at the surface is 30°C and the dew point is 5°C. Assuming that the dew point temperature does not decrease (which it does), what altitude will the cloud form at? Assume that there is dry air between the surface and the cloud.

39. Cloud formation problem #2 Answer 30° -5° = 25° Dry air cools 10° C for every 1000 meters. So, the cloud will form at 2500 meters!

40. Precipitation

41. Precipitation forms when clouds become saturated with water.

42. There are different kinds of precipitation.

43. Rain droplets grow by collision with other water droplets.

44. Drizzle is a light rain where the drops are small.

45. Ice crystals or super cooled droplets usually form in clouds.

46. If the flake does not melt before hitting the ground, we call this snow.

47. Sleet are raindrops that re- freeze as they fall through the sky.

48. Freezing rain is when rain freezes instantly when hitting the ground.

49. HailHail is frozen ice that grows in updrafts and downdrafts of thunderstorms. It finally becomes too heavy and falls to the ground. Hail

50. Precipitation is measured using a rain gauge. Snow must be melted to determine its water content.

51. Where does precipitation occur?

52. Precipitation occurs where moist air rises and cools.

53. There is little or no precipitation where air sinks and warms.

54. The rain shadow effect determines precipitation amounts. Go here for another rain shadow animation. rain shadow effect hererain shadow effect here

55. The rain shadow effect seen from the air. Picture taken on 12/31/05 on approach into LAX. Mt. San Jacinto and Palm Springs are in the distance. rain shadow effect rain shadow effect

56. The rain shadow effect as seen from visible and infrared satellite images taken on May 30, 2007. Notice the unstable cloud development (cumulonimbus clouds) over the Sierra Nevada Mountains. Also notice the stable marine layer (stratus clouds) near the coast. rain shadow effect satellite images rain shadow effect satellite images Infrared Image Visible Image

57. Average Precipitation in California

58. Dry areas occur on the east (leeward) side of mountains. Wet areas occur on the west (windward) side of mountains.

59. The Northern part of the state gets more precipitation because more low pressure storms go through that area. Central and Southern California are usually under the influence of high pressure and clear weather. See pages 422- 425 for more details on pressure patterns.

60. Water Resources: Owens Valley The Los Angeles Aqueduct System The Los Angeles Aqueduct System The Los Angeles Aqueduct System

61. Water Resources: Colorado River The Los Angeles Aqueduct System The Los Angeles Aqueduct System The Los Angeles Aqueduct System

62. Water Resources: Groundwater

63. Water Resources: Local streams and reservoirs

64. Population Growth in the Imperial Valley: Will our water resources be able to support the projected population growth? Red areas mean more and healthier crops. June 9,1973June 30,1992

65. No more water left over for Mexico? Compare the crop health in the U.S. to the crop health just across the border in Mexico. Can you see the border?

66. Go here for a water use survey! Go here for water science for schools! here