Transcript 16-4 - Laconia School District

Chapter 16 Section 4
Water in the Atmosphere
By: Trisha Kelley, Adam Cook, Chantelle
Cross, Anthony Ciampa
Humidity
Humidity is the amount of water vapor in the air.
The amount of water
vapor the air can hold depends
on the temperature in the
area. Hot air can hold more
water vapor than cold air.
At 10 degrees Celsius, one
cubic meter of air can hold a
maximum of 8 grams of water vapor.
Measuring Relative Humidity
• To measure relative humidity
you would use an instrument
called a Psychrometer. The
Psychrometer measures
relative humidity with 2
thermometers called a wet
bulb thermometer and dry bulb
thermometer. If the relative
humidity is low then the water
on the wet bulb will evaporate
slowly, and the temperature for
it won’t change much. But if
the humidity is high then the
water in the wet bulb system
will evaporate very fast and the
temperature on it will go down.
The relative humidity is found
by comparing the temperatures
on the 2 thermometers on a
relative humidity table.
The difference between humidity
and relative humidity
The difference between humidity and relative humidity is,
humidity measures how much water vapor is in the air,
while relative humidity measures how much percentage
of water vapor is in the air, compared to how much that
specific area can hold.
How Clouds Form
• Clouds form whenever air is cooled to its dew
point, particles are present, and when water
vapor in the air becomes liquid water, or ice
crystals, depending on if the dew point is below
the freezing point, or above it.
The Tops of Mountains
• Why are some of the
tops of some
mountains always
covered by clouds? The
reason the tops of some
mountains are always
covered by clouds is
because the wind is
constantly hitting the
mountain so the warm air
rises then cools, thus
creating the constant
clouds over the mountain.
Measuring Relative Humidity
• The instrument that measures relative humidity is called
a Psychrometer.
• A Psychrometer Uses 2 thermometers, one dry bulb
thermometer and one wet bulb thermometer. The wet
bulb thermometer has a wet cloth over it that is
moistened with water so when air is blown over them the
wet bulb thermometer reading drops below the dry bulb
thermometer. So if relative humidity is high, then the
water on the wet bulb thermometer wouldn’t change very
much, but if relative humidity is low then the water in the
wet bulb thermometer will evaporate rapidly. The relative
humidity can be found by comparing the two readings to
each other on a relative humidity chart.
Conditions needed for clouds to
form
• The conditions needed for clouds to form are
whenever air is cooled to it’s dew point and
when particles are present.
The three main cloud types
•
•
•
•
•
The conditions needed for clouds to form are whenever air is cooled it it’s
dew point and particle are present.
3. Describe each of the three main types of clouds. - The main cloud
types are cumulus, stratus and cirrus.
Cumulus- Cumulus clouds form less than 2 kilometers above the ground,
But may grow in size and height, as much as 18 kilometers. Cumulus
clouds are a sign of fair weather.
Stratus- Status clouds cover all or most of the sky. As a stratus cloud
thickens it may produce rain, drizzle or snow and it is then called a
nimbostratus cloud.
Cirrus- Cirrus clouds form only at high levels, above about 6 kilometers
where temperatures are very low. And as a result Cirrus clouds are made
mostly out of ice crystals.
Classifying Clouds
Each type of cloud classified as
their height level, such as
high, medium, and low.
• Altocumulus-high level
• Altostratus-medium level
• Cirrostratus-high level
• Cirrus-high level
• Cumulus-low level
• Fog-low level
• Nimbostratus- medium level
• Stratus-low level
THE END