1 raindrop = 1,000,000 cloud droplets Growth by continued condensation way too slow Collision/Coalescence (warm cloud) Cloud must contain wide range of droplet sizes with different terminal velocities Larger, faster droplets overtake smaller ones and collide Droplets grow by coalescence Process works best when Clouds have high liquid water content &#232; warm clouds Clouds are thick Updrafts are strong Ice crystal or three phase (cold cloud) Requires cloud with water in all three phases Ice nuclei required for crystals to form Ice nuclei uncommon Supercooled water droplets common Liquid at temperatures below 0 o C Saturation vapor pressure larger over water than ice Air saturated with respect to water supersaturated with respect to ice When ice crystals do form, will grow with vapor evaporated from droplets Mechanism allows for relatively rapid growth Cloud seeding Inject ice nuclei (silver iodide usually) into clouds with supercooled droplets May increase precipitation by around 10% under right conditions Hard to know when right conditions exist
(Clouds; have; high liquid water content &#232) (Ice nuclei; to form; Ice nuclei) (ice crystals; do; form) (too slow Collision/Coalescence (warm cloud) Cloud; must contain; wide range of droplet sizes) (Clouds; are; thick Updrafts) (Ice nuclei; required; for crystals; to form Ice nuclei) (water; supersaturated; ) (Larger; droplets overtake; smaller ones; T:faster) (Mechanism; allows; for relatively rapid growth Cloud seeding Inject ice nuclei (silver iodide usually) into clouds with supercooled droplets) (ice Air; saturated; with respect to water) (warm clouds Clouds are thick Updrafts; are; ) Context(warm clouds Clouds are thick Updrafts are,List([357, 398))):(strong Ice crystal or three phase; Requires; cloud with water in all three phases) (Larger; collide; Droplets grow by coalescence Process works best) Context(Larger collide,List([201, 258))):(Droplets; grow; by coalescence Process works best) (Cloud; seeding; Inject ice nuclei; into clouds with supercooled droplets) (vapor; evaporated; from droplets) (uncommon Supercooled water; droplets; common Liquid; L:at temperatures below 0 o C Saturation vapor pressure larger over water than ice Air) (Ice nuclei; will grow; with vapor)
warm clouds Clouds are thick Updrafts are,List([357, 398)) Larger collide,List([201, 258))
Clouds Ice nuclei ice crystals too slow Collision/Coalescence (warm cloud) Cloud Clouds Ice nuclei water Larger Mechanism ice Air warm clouds Clouds are thick Updrafts strong Ice crystal or three phase Larger Droplets Cloud vapor uncommon Supercooled water Ice nuclei
have to form do must contain are required supersaturated droplets overtake allows saturated are Requires collide grow seeding evaporated droplets will grow
high liquid water content &#232
Ice nuclei
form
wide range of droplet sizes
thick Updrafts
for crystals to form Ice nuclei
smaller ones T:faster
for relatively rapid growth Cloud seeding Inject ice nuclei (silver iodide usually) into clouds with supercooled droplets
with respect to water
cloud with water in all three phases
Droplets grow by coalescence Process works best
by coalescence Process works best
Inject ice nuclei into clouds with supercooled droplets
from droplets
common Liquid L:at temperatures below 0 o C Saturation vapor pressure larger over water than ice Air
with vapor