Water in the Atmosphere

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 H2O.

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.

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 = 0.50.5 X 100 = 50So 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!

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 FormationA cloud will form at the elevation where the temperature and dew point are the same.

29. Cloud StabilityFlat 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 StabilityClouds 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 StabilityInstability in a cumulonimbus cloud leads to thunderstorms, lightning, hail, flooding, wind, and tornadoes.

32. Lapse ratesA 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 ratesDry air cools at a rate of around 10°C per every 1000 meters.

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

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

36. Cloud formation problem #1The 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 #1Answer20° -10° = 10°Dry air cools 10° C for every 1000 meters.So, the cloud will form at 1000 meters!

38. Cloud formation problem #2The 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 #2Answer30° -5° = 25°Dry air cools 10° C for every 1000 meters.So, the cloud will form at 2500 meters!

40. Precipitation

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

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