Download Air Masses

Air Masses
By: Sofia Mertz
Chapter 6, Lesson 1 and 2
Kinds of air masses
An air mass: is a large body of air with similar
properties all through it. The most important
properties are temperature and amount of water
vapor. These are the types of air masses.
Continental Polar Air: Has very little water
evaporates from the land and ice near the poles. So,
an air mass from this area is cold and fairly dry.
Continental Tropical Air: a large hot dessert can
cause the air above it to be warm and fairly dry.
Maritime Polar Air: Even though the ocean near the
poles is cold, water vapor evaporates into the air.
An air mass forming over the ocean near the poles is
cold, but relatively moist.
Maritime Tropical Air: Humid air has lots of moisture.
Over tropical oceans or rain forests, an air mass
becomes warm very humid because water can easily
evaporate there.
Types of Pressure
Atmospheric pressure /air pressure: is the weight
of air pushing down on an area.
Atmospheric pressure changes with height because
the amount of air above each level is different.
As you go higher in the atmosphere, there is less air
above you to push down on you.
Air pressure decreases as you go up. Lower air
pressure means fewer air particles in a given
location.
Convection Currents
Convection current: is the rising and sinking of
matter in a circular pattern. Temperature
differences in air cause wind, storms, and all
types of weather.
Wind: is movement of air that happens because
of differences in air pressure caused by
temperature differences.
When air masses meet
Have you ever seen a line of clouds move from
the horizon until it’s over head? What you have
probably seen is the arrival of a front.
Front: is a boundary between two air masses.
Most air masses move from west to east over
North America, so fronts have the same motion.
What is a Cyclone?
On the Earth’s surface, high pressure air surrounds
warm, low- pressure air. The high pressure causes the
warm air in the center to rise. As the air rises, the
high pressure air around it flows in to takes it place.
This flow of air forms a wind that spirals inward and
forms a weather system called a cyclone.
There is also anticyclones. They form in areas of
higher pressure. Winds in a anticyclone spin the
opposite direction than a cyclone. North of the
equator, this means winds from an anticyclone flow in
a clockwise direction and away from the center.
Thanks for
watching!