Chapter 9: Weather Chapter 9: Weather FactorsFactors

Section 3: Winds

What is Wind?What is Wind?Wind – horizontal movement; from

high pressure to lower pressure.◦Caused from differences in pressure

Difference in pressure – caused by unequal heating of the atmosphere.

Measuring WindMeasuring WindWinds are described by their

direction and speed.Name of wind – Where it comes

from

Measuring WindMeasuring WindWind speed is measured with an

anemometer.

Wind-Chill FactorWind-Chill FactorWind-Chill Factor – the increased

cooling caused by wind.

Local WindsLocal WindsLocal Winds – blow over short

distances.◦Caused by unequal heating of

Earth’s surface within a small area.◦Form only when large scale winds

are weak.

Local WindsLocal WindsSea Breeze (Lake Breeze) – a local

wind that blows from an ocean or lake.

Local WindsLocal WindsLand Breeze – flow of air from

land to a body of water.

Global WindsGlobal WindsGlobal Winds – winds that blow

steadily from specific directions over long distances.◦Created by unequal heating of Earth’s

surface but occur over a large area.

Global Convection Global Convection CurrentsCurrentsGlobal Convection Currents –

Temperature differences between the equator and the poles produce giant convection currents in the atmosphere.

Global Convection Global Convection CurrentsCurrentsCoriolis Effect – Earth’s rotation

makes winds curve.

Global Wind BeltsGlobal Wind BeltsDoldrums – Near Equator; Calm

area; warm air rises; low pressure area

Horse Latitudes – Calm area; falling air; high pressure

Trade Winds – blow from horse latitudes toward the equator

Prevailing Winds – blow away from the horse latitudes toward the poles