1. Precipitation
18.3
Brain Pop:
Snowflakes
Brain Pop:
Rainbows

2. How Precipitation Forms
Cloud droplets = < 20 micrometers. They must grow in volume by roughly 1 million times for precipitation to form.

3. Cold Cloud Precipitation
Burgeron Process: Theory that relates the formation of precipitation to two physical processes – supercooling and supersaturation

4. Supercooled water: the condition of water droplets that remain in the liquid state at temperatures well below 0oC
Water will freeze if it comes in contact with a solid object (freezing nuclei)
Supersaturated air: the condition of air that is more highly concentrated than normally possible  relative humidity is > 100%

5. Warm Cloud Precipitation
Collision-Coalescence Process: Theory that says large cloud droplets collide and join together with smaller droplets to form a raindrop. Opposite electrical charges may bind the cloud droplets together.

6. Forms of Precipitation
The type of precipitation that reaches Earth’s surface depends on the temperature profile in the lowest few kilometers of the atmosphere

7. Drizzle: < 0.5 mm in diameter. Fall slowly & close together

8. Rain: >0.5 mm in diameter.
Fall faster & farther apart

9. Snow: six-sided ice crystals
Air temp < -5oC & air is drier
 light fluffy snow
Air temp > -5oC & air is wetter
 thick clumps of snow

10. Sleet: When a layer of freezing air overlies subfreezing air near the ground, small particles of ice fall.

11. Glaze: When raindrops become supercooled (below 0oC) as they fall, then turn to ice on impact. A.K.A. freezing rain.

12. Hail: Ice pellets formed in cumulonimbus clouds
Hail: Ice pellets formed in cumulonimbus clouds. Form layers of ice if carried upward by a strong updraft.

13. rain gauge: Instrument used to measure the amount of rainfall