Cloud Seeding - Addition of Ice Nuclei to a Cold Cloud

  • To add more ice nuclei to the cloud, simply fly an airplane over it or under the updraft and release ice nuclei:

    • silver iodide

    • dry ice

  • It is possible to release to many ice nuclei into the cloud:
    • in this situation, you will have many small ice particles competing for vapor to grow
    • there there is not enough vapor, then you end up with a cloud full of small ice particles
    • can't grow to precip size - suppressed precipitation!!
  • It's also possible to naturally seed clouds


1.  Suppose that a thick nimbostratus cloud contains ice crystals and cloud droplets all about the same size. Which precipitation process will be most important in producing rain from this cloud? Why?

2.  When cirrus clouds are above a deck of altocumulus clouds, occasionally a clear area, or "hole," will appear in the altocumulus cloud layer. What do you suppose could cause this to happen?

3.  During a recent snowstorm, Denver, CO received 7 cm of snow. 60 km east of Denver, a city received no measurable snowfall, while 150 km east of Denver another city received 10 cm of snow. Since Denver is located to the east of the Rockies, and the upper-level winds were westerly during the snowstorm, give an explanation as to what could account for this snowfall pattern.