Ch. 23.3 WindsCh. 23.3 Winds

Low air pressure at the equator, due Low air pressure at the equator, due to the constant rising of heated air.to the constant rising of heated air.

Cold heavy air at the poles sinks, Cold heavy air at the poles sinks, causing high pressure regions.causing high pressure regions.

Pressure differences create Pressure differences create worldwide air movement (winds)…air worldwide air movement (winds)…air moves from high pressure to low moves from high pressure to low pressure.pressure.

Global WindsGlobal Winds

The The Coriolis forceCoriolis force causes winds to be causes winds to be deflected to the deflected to the rightright in the in the N. HemisphereN. Hemisphere, and to the left in , and to the left in the S. Hemisphere. the S. Hemisphere. Greatest effect Greatest effect at the poles.at the poles.

Warm air rising at the equator Warm air rising at the equator spreads poleward in both directions.spreads poleward in both directions.

Some sinks at 30 degrees latitude, Some sinks at 30 degrees latitude, forming high pressure zones with air forming high pressure zones with air flowing away both north and south.flowing away both north and south.

At 60 degrees latitude, surface air At 60 degrees latitude, surface air from the polar highs meets the air from the polar highs meets the air flowing from the 30 degree highs.flowing from the 30 degree highs.

Converging air rises, forming low Converging air rises, forming low pressure areas at 60 degrees pressure areas at 60 degrees latitude.latitude.

The three looping patterns of flow in The three looping patterns of flow in each hemisphere are called each hemisphere are called convection cellsconvection cells..

Look up and define: trade winds, Look up and define: trade winds, doldrums, horse latitudes, westerlies, doldrums, horse latitudes, westerlies, polar easterliespolar easterlies

Wind and Pressure ShiftsWind and Pressure Shifts

Yearly seasonal cycles mean that the Yearly seasonal cycles mean that the global wind belts shift about 10 global wind belts shift about 10 degrees of latitude during the course degrees of latitude during the course of a year.of a year.

Local WindsLocal Winds

BreezesBreezes—gentle winds that extend —gentle winds that extend less than 100 km.less than 100 km.

Often caused by local conditions that Often caused by local conditions that produce temperature differences.produce temperature differences.

Land and Sea BreezesLand and Sea Breezes

Land heats up faster than water Land heats up faster than water when both receive equal sunlight.when both receive equal sunlight.

During daylight, warmed air above During daylight, warmed air above land rises, creating low pressure.land rises, creating low pressure.

Cooler air from over the water moves Cooler air from over the water moves in to replace it…a in to replace it…a sea breezesea breeze..

At night, the reverse occurs, the land At night, the reverse occurs, the land cools faster, and a cools faster, and a land breeze land breeze develops.develops.

Mountain and Valley BreezesMountain and Valley Breezes

During daytime, warmed air in During daytime, warmed air in valleys moves up mountain slopes…a valleys moves up mountain slopes…a valley breeze.valley breeze.

At night, in the quickly cooling At night, in the quickly cooling mountains, cold mountain air flows mountains, cold mountain air flows downhill into the valleys, a downhill into the valleys, a mountain mountain breezebreeze..