Pre-Activity (Air Pressure Systems)

Air Pressure Systems

Use the links for each topic to answer the associated questions...

Atmospheric Pressure	What causes atmospheric pressure to change? What is average atmospheric pressure at sea level? Atmospheric pressure is commonly known as what?
Units of Pressure	What units do meteorologists use to measure atmospheric pressure? What are other units that atmospheric pressure is often noted in?
Get Your Current Local Barometric Pressure	Look at your local weather and find out the current atmospheric pressure. (If your pressure reading is not available use one from another nearby city)
Conversion Calculator	Convert your local atmospheric pressure reading to millibars and atmospheres. Is your local pressure reading greater or less than the average pressure at sea level?
Looking at Atmospheric Pressure on Maps	Atmospheric Pressure is often noted as lines or colored contours on maps. What are these lines called?

Use the picture below to answer the following questions...

What is the atmospheric pressure reading in the center of the low pressure cell?
What is the atmospheric pressure reading in the center of the high pressure cell?
Note which direction winds circulate in this picture around the low and high pressure cells.

(For more information on Low Pressure Cells and High Pressure Cells click on the links in the picture)

This AVN Surface Pressure Forecast image, taken on April 6, 1999
at 12:00 Greenwich Mean Time, shows two distinct pressure cells.
(This image offers a snapshot of conditions that occurred at a specific time and date.)

Low Pressure Cell
Winds circulate counter-clockwise
Pressure decreases inward

High Pressure Cell
Winds circulate clockwise
Pressure increases inward