Chapter 7: Precipitation

What is the most problem causing form of precipitation

Freezing Rain

How do cloud droplets develop?

Water vapor molecules adhere to condensation nuclei and will cool, condense, & form cloud droplets

What are the other two methods of growing precipitation besides condensation?

Collision and Coalescence Process (warm cloud process) & Bergeron Process (cool cloud process)

Cumulonimbus clouds

Have lots of moisture, drops of all sizes, strong updrafts, and highly charged particles - and are efficiently producers of precipitation

What are factors that determine rainfall in Collision and Coalescence Process

range of droplet sizes

cloud thickness

updrafts in the cloud

electrical charges

What is the Collision and Coalescence Process?

Collisions between cloud drops of different sizes grow rain drops in warm clouds

What is the Bergeron Process?

This is an ice-crystal process that produces precipitation

Clouds with both ice and water are called “mixed clouds”

Some water droplets are existing at temperatures below freezing - they are: supercooled

Accretion

Ice crystals can collide with supercooled drops and cause instant freezing to form graupel (snow pellets)

Doppler Radar

Weather radar detects and displays areas of precipitation

Tipping Bucket Rain Gauge

Two tiny buckets fill with 0.01” of rain at a time, tipping back and forth

Each time a bucket is emptied, an electronic contact is made with a “pen” and records the rainfall measurement