Download 4.6 Investigating Weather

4.6 Investigating Weather
There are many tools we use to
determine the weather
A thermometer measures the
temperature of the air
A water gauge measures how much
water fell as rain or snow
An anemometer measures the speed of
the wind
A barometer measures air pressure
Meteorologists use the data they collect with
these instruments to predict our weather
Air pressure - Half of the air making up our atmosphere is
squished down into the first three layers, and 90% of the
atmosphere is squished into the first 10 miles (16km). Above
this altitude the air is so thin that the pressure is even less
than that of the best vacuums on the surface of the Earth.
What is a High Pressure System?
A high pressure system is a whirling mass of cool, dry air
that generally brings fair weather and light winds. When
viewed from above, winds spiral out of a high-pressure
center in a clockwise rotation in the Northern Hemisphere.
These bring sunny skies. A high pressure system is
represented as a big, blue H.
What is a Low Pressure System?
A low pressure system is a whirling mass of warm, moist air
that generally brings stormy weather with strong winds. When
viewed from above, winds spiral into a low-pressure center in
a counterclockwise rotation in the Northern Hemisphere. A
low pressure system is represented as a big, red L.
What is an air mass?
An air mass is an extremely large body of air whose
properties of temperature and moisture content
(humidity), at any given altitude, are fairly similar
in any horizontal direction. Air masses can cover
large (hundreds of miles) areas. Air masses can
control the weather for a relatively long time
period: from a period of days, to months.
What is a front?
A front is a boundary between two different air masses,
resulting in stormy weather. A front usually is a line of
separation between warm and cold air masses.
When warm air rises, cold air moves in
replacing the warm air. This movement of air
is what we call wind.
There are 4 different cloud formations you
should know. Cirrus clouds are wispy/feathery
and they mean nice weather is coming our way
Stratus clouds are grayish clouds that often
cover the entire sky. They resemble fog that
doesn't reach the ground. Light mist or
drizzle sometimes falls out of these clouds.
Cumulus clouds are white, puffy clouds that
look like pieces of floating cotton. These
clouds grow upward and they can develop
into giant cumulonimbus clouds, which are
thunderstorm clouds.
Cumulonimbus clouds are thunderstorm
clouds. High winds can flatten the top of the
cloud into an anvil-like shape. Cumulonimbus
clouds are associated with heavy rain, snow,
hail, lightning and even tornadoes.
Can you name these clouds?
The basic ingredients used to make a
thunderstorm are moisture, unstable air and
lift. You need moisture to form clouds and
rain. You need unstable air that is relatively
warm and can rise rapidly.
Hurricanes gather heat and energy through
contact with warm ocean waters.
Evaporation from the seawater increases
their power.
Most tornadoes form from thunderstorms. You need
warm, moist air from the Gulf of Mexico and cool,
dry air from Canada. When these two air masses
meet, they create instability in the atmosphere.