Precipitation
Clouds made of water droplets < 10 micrometers in diameter
Fall incredibly slow
Formation of precipitation
1. Bergeron process
a. Temperature in cloud is below freezing – supercooled water
b. Ice crystals collect water vapor
c. Large snowflakes form and fall as snow or melt and form rain
d. Mid and High latitudes
2. Collision-coalescence
a. Warm clouds
b. Large condensation nuclei form large drops
c. Droplets collide with other droplets
d. Tropical regions
Forms of precipitation
1. Rain and drizzle
a. Rain - droplets > .5 mm
b. Drizzle < .5 mm
2. Snow – ice crystals, or groups of ice crystals
3. Sleet and glaze
a. Sleet – small particles of ice
Warmer air over colder air -- water falls hits colder air and freezes
b. Glaze – rain freezes on impact with cold object
4. Hail
a.
b.
c.
d.
Frozen ice balls
Formed in layers within cumulonimbus clouds
Strong winds blow frozen drops up to be coated by more ice
Eventually falls when wind cannot keep hail from falling
5. Rime
a. Freezing of supercooled fog
Precipitation measured by
Rain gauge
Funnel and cylinder in proper ratio
Snow
a. Depth
b. Melted units -- St. Louis area 10 inches snow = 1 inch melted
Varies by location (ex. Wet snow versus dry snow)