Chapter 2: Weather Factors
Section 5: Precipitation
Precipitation: any form of water that falls from clouds and reaches Earth’s surface
Rain Gauge: open-ended can or tube that collects rainfall
Droughts: long periods of unusually low precipitation
Cloud seeding: a man-made way to produce rain
Transpiration: adding water to the atmosphere through plants
Water cycle: movement of water between surfaces and the atmosphere
Meteorologist: person who studies the weather
Important Facts:
 Air masses are in constant motion
 Meteorologists measure rain with a rain gauge
 Common types of precipitation include rain, sleet, freezing rain, hail and snow
I. Rain
A.
B.
C.
D.
Most common form of precipitation
Drops of water at least .5mm in diameter
Mist/drizzle (smaller drops)
Fall from nimbostratus clouds
II. Sleet
A. Forms when rain drops fall through a layer of air 0 degrees C or
colder and freeze into solid particles
B. Become solid particle of ice
C. Smaller than 5mm in diameter
III. Freezing Rain
A. Raindrops that freeze when they touch a cold surface
B. Forms a glaze on surfaces
C. Glaze: smooth, thick layer of ice built up on surfaces
IV. Hail
A. Round pellets of ice larger than 5 mm in diameter
B. Only from in cumulonimbus clouds
C. How do they form?
1. Starts as an ice pellet
2. Strong winds (updraft) cause pellets to rise up through
cold layers of air
3. as moisture is added, it freezes, adding another layer of
ice
4. eventually the hailstone becomes too heavy and falls to
the ground
D. Hail stone can become very large and cause a lot of damage
V. Snow
A. Water vapor converted directly into ice crystals (snowflakes)
B. Snowflakes have endless patterns
C. 6 sides
Essay: How does fog form?
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After a warm, humid day there is water vapor in the air
The ground cools at night because the sun is no longer heating it
This causes the air to cool to the dew point
Water vapor in the air condenses into particles
Droplets form and come together to create a cloud at ground level (FOG)
When the sun comes up- it heats the droplets (liquid water)
The sun evaporates the water and causes it to turn back into water vapor (gas)