Rain Drops, Cloud Droplets, and CCN
- Recall the relative sizes of rain
drops, cloud drops, and CCN:
- raindrops - 2000 mm = 2 mm
- fall at a speed of 4-5 ms-1
- cloud drops - 20 mm = 0.02 mm
- remain suspended in the air
- CCN - 0.2 mm = 0.0002 mm
- remain suspended in the air
- raindrops - 2000 mm = 2 mm
- To get a droplet (20 mm)
to grow to raindrop size (2000mm)
it must increase in size by a factor of 100 (two
orders of magnitude):
- 2000mm/20mm = 100
- this occurs in about 30 minutes in a thunderstorm!!!
- this is like a 150 lb person growing in size to 15,000 lbs in half an hour!!!
- Q: How does this happen??
