Air PressureAir Pressure

The pressure The pressure exerted on an exerted on an object by the air.object by the air.– Occurs in all Occurs in all

directions directions up, down, up, down, sidewayssideways

Air PressureAir Pressure

A barometer is A barometer is used to measure used to measure the amount of the amount of pressure in the pressure in the air.air.– Units = mmHg Units = mmHg

(millimeters of (millimeters of Mercury) or atm Mercury) or atm (atmospheres)(atmospheres)

BarometersBarometers

Rapidly falling pressure almost always Rapidly falling pressure almost always means an approaching storm system. means an approaching storm system.

Rapidly rising pressure almost always Rapidly rising pressure almost always means clearing and cooler weather is means clearing and cooler weather is ahead. ahead.

WindsWinds Winds are created Winds are created

by horizontal air by horizontal air pressure pressure differences – differences – pressure pressure gradientsgradients

Uneven heating Uneven heating of the Earth of the Earth creates pressure creates pressure differencesdifferences

What affects wind?What affects wind?

Pressure differences- Cause air to Pressure differences- Cause air to movemove

The Coriolis Effect- causes global The Coriolis Effect- causes global winds to be deflectedwinds to be deflected

Friction- slows down air, which Friction- slows down air, which changes wind directionchanges wind direction

Measuring PressureMeasuring Pressure Isobars- lines of equal pressureIsobars- lines of equal pressure

– Much like contour lines, but instead of Much like contour lines, but instead of elevation, they are lines of equal pressureelevation, they are lines of equal pressure

– Are used to predict where weather is Are used to predict where weather is movingmoving

Jet StreamJet Stream

Fast flowing, Fast flowing, relatively narrow relatively narrow air currents found air currents found just under the just under the tropopause tropopause

Form at the Form at the boundaries of boundaries of adjacent global adjacent global wind beltswind belts

Global WindsGlobal Winds Global winds are Global winds are

created by the created by the unequal heating of unequal heating of Earth.Earth.

The equator is The equator is much hotter than much hotter than the rest of Earth, the rest of Earth, causing an causing an extremely low extremely low pressure.pressure.

Global WindsGlobal Winds This causes air from This causes air from

adjacent areas to adjacent areas to move towards the move towards the equator.equator.

This movement This movement begins a chain begins a chain reaction of air reaction of air movement movement throughout Earth, throughout Earth, creating 6 wind creating 6 wind belts.belts.

High Pressure Zone/CycloneHigh Pressure Zone/Cyclone

Occurs when Occurs when temperatures are coldtemperatures are cold

Little or no moisture Little or no moisture (humidity)(humidity)– The air is heavy and The air is heavy and

sinks towards Earth’s sinks towards Earth’s surfacesurface

Winds move outward Winds move outward and clockwise around and clockwise around the center of a cyclonethe center of a cyclone

Low Pressure Zone/AnticycloneLow Pressure Zone/Anticyclone

Occurs when Occurs when temperatures are warmtemperatures are warm

Can have large Can have large amounts of moisture amounts of moisture (humidity)(humidity)– The air is light and rises The air is light and rises

upward into the upward into the atmosphereatmosphere

Winds move outward Winds move outward and counterclockwise and counterclockwise around the center of around the center of the anticyclonethe anticyclone

The Coriolis EffectThe Coriolis Effect The Coriolis effect is a The Coriolis effect is a

result of the spinning of result of the spinning of Earth. Earth.

As Earth spins, anything As Earth spins, anything moving in a straight line moving in a straight line from North to South will from North to South will be deflected sideways.be deflected sideways.– In the Northern In the Northern

Hemisphere, winds, Hemisphere, winds, water, and other fluids water, and other fluids will be deflected to the will be deflected to the right at a 90right at a 90oo angle. angle.

– In the Southern In the Southern Hemisphere, everything Hemisphere, everything will be deflected to the will be deflected to the left at a 90left at a 90oo angle. angle.

AssignmentAssignment

Complete procedure questions for “Air Complete procedure questions for “Air Pressure Demonstration”Pressure Demonstration”

Identify Types of Energy Transfers Identify Types of Energy Transfers WorksheetWorksheet