1. Ch. 24.4 Water in the Atmosphere
Objectives:
What are some ways in which water condenses?
How do clouds form?
What are major cloud types?
What are the major forms of precipitation?

2. Humidity = Amount of water vapor in air
Warm tropical air contains more water than cold, polar air
Relative Humidity = Ratio of the amount of water vapor in the air to the maximum amount of water vapor that can exist as that temperature.
Expressed as a %
Ex.: Relative Humidity is 60%, Air contains 60% of maximum amount of water vapor that can exist at that temperature
Relative humidity = 100 %, Air is SATURATED

3. Relative Humidity & Dew Point
Warmer air can hold more water
As temps. decrease (at night), amt. of water air can hold decrease and relative humidity increases. During day, temps. increase and relative hum. Decreases.
(even though the total amount of water in air stays the same).

4. DEW POINT =
Temp. at which air is SATURATED (RELATIVE HUMIDITY 100%).
If temps. Drop further  water vapor condenses (air can’t hold any more water)

5. Water condenses at Dew Point (temperature)
Dew – water vapor condenses on earth’s surface.
Frost – dew point of air is below freezing.
Water doesn’t condense. G  S (ice)
Fog – water vapor condenses to form a cloud that is near / touching ground
Clouds

6. Cloud Formation
Clouds = dense, visible mass of tiny water droplets or ice crystals (very small) that are suspended in the atmosphere.
Cloud formation:
Warm, moist air rises in atmosphere
Water vapor condenses when temp. drop below dew point.
3. Condensation Nuclei – also needed
Dust, salt, solid particles needed as platforms for water to condense on.

7. Cloud Type: Cumulus
Cumulus Clouds – Puffy, piles/heaps of cotton balls w/ flat bottoms.
“fair weather clouds”
Form less than 2 kms. From ground
Cumulonimbus = Dark towering clouds that are ass. w/ thunder storms. Grow vertically. (Anvil top) “Thunder heads”

8. Cloud Type: Stratus
Stratus Clouds – Flat layers, cover much or all of sky
Nimbostratus = low stratus that produce steady, widespread rain or snow.
Altostratus = Middle level clouds (2000 – 6000 meters) that produce light rain or snow.

9. Cloud Type: Cirrus
Cirrus Clouds = Thin wispy feathery /veil like clouds made up of ice crystals.
Clear sunny days
Don’t produce rain … but are usu. Ahead of rain producing clouds.
High Altitudes
Link to chart:

12. Forms of Precipitation
Rain = liquid precip. Forms in nimbostrat. or cumulonibus clouds
Snow = ice cystals
Hail = round, solid pieces of ice more than 5 mm in diameter. Ice is tossed up & down in cumulonimbus clouds and get coated w/ water that freezes  layers of ice.
Sleet = Ice particles less than 5mm in diamter. Rain freezes as it falls.
Freezing Rain = rain freezes after hitting surfaces.

13. 1.

14. 2.

15. 3.

16. 4.