Download Pressure station

Atmospheric Pressure:
(remember to takes notes and observations in your ISN)
High vs. Low Pressure System Explained
An important characteristic of the Earth's atmosphere is its air pressure as it
often determines wind and weather patterns across the globe. By definition,
atmospheric or air pressure is the force per unit of area exerted on the Earth’s
surface by the weight of the air above the surface. The force exerted by an air
mass is created by the molecules that make it up and their size, motion, and
number present in the air. These are important factors because they determine
the temperature and density of the air and thus its pressure.
The number of air molecules above a surface determines air pressure. As the
number of molecules increases, they exert more pressure on a surface and the
total atmospheric pressure increases. By contrast, if the number of molecules
decreases, so too does the air pressure.
Today, air pressure is often measured with a mercury or aneroid barometer. A
mercury barometer measures the height of a mercury column in a vertical glass
tube.
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 highpressure center in a clockwise rotation in the Northern Hemisphere. These bring
sunny skies. A high pressure system is represented as a big, blue H.
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.
L
Visit: The Highs and Lows of Air Pressure
Answer the following questions:
1) What is air pressure the measure of?
2) If you are on top of a mountain, is there more or less air pressure than at
sea level? Why?
3) What causes air pressure to change from day-to-day?
4) When an area is warmed, what happens to the air and the air pressure?
What kind of pressure system is formed?
5) What kind of air pressure system is known for good weather? Why does
this pressure cause good weather? What direction do the winds swirl in
this system? How is this system indicated on a map?
6) What tools are used to measure air pressure? What units are used to
describe air pressure?