1. PRECIPITATION & WEATHER MODIFICATION
ATM OCN Fall 2001 LECTURE 15
PRECIPITATION &
WEATHER MODIFICATION
A. INTRODUCTION Statement of the Problems
Why no precipitation?
Can humans cause rain?

2. H. WEATHER MODIFICATION BACKGROUND
Statement of Problem
Why no precipitation?
Can humans cause rain?
For precipitation, need:
sufficient atmospheric humidity;
a cloud;
sufficiently large raindrops/snowflakes to fall & reach ground as rain or snow.

3. INTENTIONAL ARTIFICIAL WEATHER MODIFICATION
Goals
Stimulate Precipitation
Dissipate Clouds & Fog
Suppress Hail
Modify Hurricanes

4. C. WEATHER MODIFICATION (con’t.)
Precipitation Stimulation Techniques - "Cloud seeding"
Early Weather Modification Techniques
Modern Precipitation Stimulation Strategies
Problems
Scientific
Legal

5. TYPICAL STRATEGIES
WARM CLOUDS
Add large hygroscopic nuclei.
COLD CLOUDS
Freeze all supercooled droplets with Dry Ice (Solid CO2);
Add freezing nuclei with ice-like crystal structure with Silver Iodide (AgI).