Air Pressure The pressure exerted on an object by the air. – Occurs in all directions up, down, sideways
Air Pressure A barometer is used to measure the amount of pressure in the air. – Units = mmHg (millimeters of Mercury) or atm (atmospheres)
Barometers Rapidly falling pressure almost always means an approaching storm system. Rapidly rising pressure almost always means clearing and cooler weather is ahead.
Winds Winds are created by horizontal air pressure differences – pressure gradients Uneven heating of the Earth creates pressure differences
What affects wind? Pressure differences- Cause air to move The Coriolis Effect- causes global winds to be deflected Friction- slows down air, which changes wind direction
Measuring Pressure Isobars- lines of equal pressure – Much like contour lines, but instead of elevation, they are lines of equal pressure – Are used to predict where weather is moving
Jet Stream Fast flowing, relatively narrow air currents found just under the tropopause Form at the boundaries of adjacent global wind belts
Global Winds Global winds are created by the unequal heating of Earth. The equator is much hotter than the rest of Earth, causing an extremely low pressure.
Global Winds This causes air from adjacent areas to move towards the equator. This movement begins a chain reaction of air movement throughout Earth, creating 6 wind belts.
High Pressure Zone/Cyclone Occurs when temperatures are cold Little or no moisture (humidity) – The air is heavy and sinks towards Earth’s surface Winds move outward and clockwise around the center of a cyclone
Low Pressure Zone/Anticyclone Occurs when temperatures are warm Can have large amounts of moisture (humidity) – The air is light and rises upward into the atmosphere Winds move outward and counterclockwise around the center of the anticyclone
The Coriolis Effect The Coriolis effect is a result of the spinning of Earth. As Earth spins, anything moving in a straight line from North to South will be deflected sideways. – In the Northern Hemisphere, winds, water, and other fluids will be deflected to the right at a 90o angle. – In the Southern Hemisphere, everything will be deflected to the left at a 90o angle.
Assignment Complete procedure questions for “Air Pressure Demonstration” Identify Types of Energy Transfers Worksheet