15-3 Atmospheric Pressure15-3 Atmospheric Pressureand Winds and Winds

pgs. 402-407pgs. 402-407IN: What causes winds?IN: What causes winds?

Terms to Learn and Terms to Learn and ObjectivesObjectives• Terms:Terms:

WindWind Coriolis Coriolis effecteffect trade windstrade windswesterlieswesterlies polar easterlies polar easterlies

jet streamsjet streams

• Objectives:Objectives:

• Explain the relationship between air Explain the relationship between air pressure and wind direction.pressure and wind direction.

• Describe the global patterns of wind.Describe the global patterns of wind.

• Explain the causes of local wind Explain the causes of local wind patterns.patterns.

• Wind is moving air created by Wind is moving air created by differences in air pressure.differences in air pressure.– The greater the pressure difference, the The greater the pressure difference, the

faster the wind moves.faster the wind moves.

Pressure Belts – Pressure Belts –

• As warm air rises over the equator, it As warm air rises over the equator, it begins to cool and begins to sink begins to cool and begins to sink causing a high-pressure beltcausing a high-pressure belt

• At the poles, cold air sinks and moves At the poles, cold air sinks and moves away along the surface. As it warms, it away along the surface. As it warms, it begins to rise causing low-pressure begins to rise causing low-pressure beltbelt

Pressure BeltsPressure Belts

• The rotation of the earth causes the The rotation of the earth causes the Coriolis Effect Coriolis Effect which causes wind to which causes wind to travel in a curved path rather than a travel in a curved path rather than a straight line.straight line.

Types of WindsTypes of Winds

• Local windsLocal winds move short distances move short distances and can blow from any directionand can blow from any direction

• Global windsGlobal winds are part of a pattern are part of a pattern of air circulation that moves in a of air circulation that moves in a specific direction across the Earth.specific direction across the Earth.

• Trade Winds – the wind that blows in Trade Winds – the wind that blows in both hemispheres from 30both hemispheres from 30° latitude ° latitude to the equatorto the equator

• Doldrums are an Doldrums are an area of low pressure area of low pressure around the equator around the equator where the trade where the trade winds of both winds of both hemispheres meet.hemispheres meet.

• Horse latitudes are Horse latitudes are an area of high an area of high pressure at about pressure at about 3030° north and south ° north and south caused by sinking caused by sinking air.air.

• Westerlies are wind belts found in Westerlies are wind belts found in both hemispheres between 30both hemispheres between 30° and ° and 60° latitude and flow toward the 60° latitude and flow toward the poles in the opposite direction of the poles in the opposite direction of the trade winds.trade winds.

• Polar Easterlies are wind belts Polar Easterlies are wind belts formed from cold, sinking air that formed from cold, sinking air that extend from the poles to 60extend from the poles to 60° latitude ° latitude in both hemispheres.in both hemispheres.

• Jet Streams are narrow belts of wind Jet Streams are narrow belts of wind that blow in the upper troposphere that blow in the upper troposphere and lower stratosphere. They may and lower stratosphere. They may reach speeds of 500 km/h and do not reach speeds of 500 km/h and do not follow regular paths.follow regular paths.

• Local winds are influenced by the Local winds are influenced by the geography of an area.geography of an area.– Areas such as shorelines and mountains Areas such as shorelines and mountains

sometimes produce temperature sometimes produce temperature differences that cause windsdifferences that cause winds

Question 1Question 1

•What causes winds?What causes winds?

AnswerAnswer

•Winds are caused by Winds are caused by the uneven heating of the uneven heating of Earth’s surface, which Earth’s surface, which causes pressure causes pressure differencesdifferences

Question 2Question 2

•What are the three What are the three types of global winds?types of global winds?

AnswerAnswer

•Polar EasterliesPolar Easterlies

•WesterliesWesterlies

•Trade WindsTrade Winds

Question 3Question 3

•What is the What is the difference between a difference between a land breeze and a sea land breeze and a sea breeze?breeze?

AnswerAnswer

•Sea breezes occur during Sea breezes occur during the day when the land is the day when the land is warmer than water and a warmer than water and a land breeze occurs at land breeze occurs at night when the water is night when the water is warmer than landwarmer than land