Download What is a Low Pressure System?

Air Pressure
Reminder:
What makes the weather?
• Remember: Weather is the condition of the
atmosphere at a particular time with respect to its
o Heat or Coldness
o Wetness or Dryness
o Clearness or Cloudiness
• All of Earth’s many kinds of weather depend on two
things:
o 1. Heat from the sun
o 2. Water
Weather and the Sun
• All weather, good and bad,
is the result of energy
exchange from the sun.
Every day, the Earth is
bombarded by energy from
the Sun. Nearly 40% of this
energy is reflected back into
space.
• As the earth surface is
warmed, it radiates heat
back into the air. The sun’s
rays are absorbed by both
land and sea on earth.
Sun’s Rays on
Land in the Day
• Land surfaces usually heat up faster than
water. This causes the air above land to be
quite warm during the day while the sun is
shining.
Which creates warm air that rises in
our atmosphere
Sun’s Hot Rays beam
down on Earth
They heat up the land
Sun’s Rays on
Land in the Day
• Land surfaces that are barren and dry heat up
very quickly, and radiate hot air back into our
atmosphere.
• Land surfaces filled with vegetation also heat
up, but slower than those that are barren.
Which creates hot air that rises in our
atmosphere
Sun’s Hot Rays beam
down on Earth
They heat up the land
Sun’s Rays on the Ocean
• Water heats up slower than land. However,
it maintains a fairly constant temperature in
the day and night.
Some warm air rises. This
amount is much less than
that over land. The air over
the ocean is much cooler.
Sun’s Hot Rays beam
down on the ocean
They slowly heat up the
ocean
Land temperature at night
• When the sun sets, the earth cools off
quickly since it is no longer being heated.
Without heat to radiate into the
atmosphere, the temperature drops.
Ocean temperature at
night
• Since the ocean takes longer to heat up, it also takes
longer to cool down. The air over the ocean at night is
warmer than that over the land.
The Weather
• As the air gets warmer in
the day, and cools down at
night, it causes different
temperatures, can create
winds and clouds, and
even lead to storms.
• Let’s learn more about this
in the movie, What is
weather?
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.
L
COLD AIR