Download Water in the Atmosphere - Grosse Pointe Public School System

Water in the
Atmosphere
Water in the Atmosphere
• The Water Cycle
Humidity
• Humidity is a measure of the
amount of water vapor in the air.
• The amount of water vapor that the
air can hold depends on its
temperature.
• Warm air can hold more water
vapor than cool air.
Humidity
• The percentage of water vapor in the air
compared to the maximum amount the air
could hold is called the relative humidity.
• Relative humidity can be measured
using a psychrometer.
Water in the Air
• Clouds form when water vapor in the air
becomes liquid water or ice crystals.
• The process by which molecules of water vapor
in the air become liquid water is called
condensation.
Water in the Air
• The temperature at which condensation begins is
called the dew point.
• Clouds form whenever air is cooled to its dew point
and particles are present.
Types of Clouds
• Meteorologists classify clouds into three main
types (shapes):
– 1. Cumulus
– 2. Stratus
– 3. Cirrus
• Clouds are also classified by their altitude.
• Each type of cloud is associated with a
different type of weather.
Cumulus
• Clouds that look like fluffy, rounded piles of cotton
are called cumulus clouds.
• Cumulus clouds usually indicate fair weather.
• Towering clouds with flat tops, called cumulonimbus
clouds, often produce thunderstorms.
Stratus
• Clouds that form in flat layers are called stratus clouds.
• As stratus clouds thicken, they may produce drizzle, rain,
or snow.
• They are then called nimbostratus clouds.
Cirrus
• Wispy, feathery clouds are called cirrus clouds.
• Cirrus clouds form only at high levels, where
temperatures are very low.
• As a result, cirrus clouds are made of ice crystals.
• Cirrocumulus clouds often indicate that a storm is
on its way.
Lenticular Clouds
• Air gets pushed upward where it cools and
condenses into clouds.
• Depending on how smooth the flow is, you
can get some amazing clouds formations
Mammatus Clouds
• Clouds that form at or near the ground are
called fog
• Fog often forms when the ground cools at
night after a warm, humid day