WINDS

What is Wind? A horizontal movement of air Vertical movements of air are currents or updrafts or downdrafts.

What is the role of Wind? Moves excess heat from tropics to poles Moves water vapor from ocean to land Moves ocean currents Creates waves on the ocean or other bodies of water

What causes wind? Unequal heating of the Earth Pressure differences because of temperature differences Winds blow from high to low pressure areas.

What factors affect wind direction? Pressure gradient Coriolis Effect (to the right in the northern hemisphere) Friction (slows surface wind speed and weakens Coriolis effect)

Winds in Pressure Systems High Pressure: Clockwise and outward Low Pressure: Counter-clockwise and inward

Global Wind Belts

Global Wind Belts Caused by the Coriolis Effect and Unequal Heating of the Earth Cold, heavy air sinks Warm, expanding air rises More sun at the equator causes air to rise and move toward the poles The Coriolis Effect causes global winds to turn in certain directions. Occur over a large area

Three main global wind belts Trade Winds: occur between 30o N and S of the equator; blow west from the NE in the N. Hemisphere and from the SE in the S. Hemisphere Prevailing Westerlies: occur between 30o and 60o N and S of the equator; blow east from the SW in the N. Hemisphere and NW in the S. Hemisphere Polar Easterlies: occur between 60o and 90o N and S of the equator; blow west along the polar front; the mixing of warm air and cold air has an impact on weather in the United States.

Areas of No Wind Doldrums: located along the equator because warm air rises creating a low pressure system Horse latitudes: at 30o N and S of the equator; weak winds; many deserts occur here because of the dry air

Jet Streams Narrow belts of high speed winds that blow in the upper troposphere and lower stratosphere about 10 km up in the atmosphere (wind speed: 200-400 km/hr) Separates warm air from cold air Two per hemisphere: polar and subtropical Winds blow from W to E but shift N and S Have an effect on the movement of weather systems.

Local Winds Sea Breezes: H pressure over the ocean and L pressure over the land cause air to move from the water to the land as warm air rises and cold air from the water comes in to take its place (DAY time) Land Breezes: H pressure over the land and L pressure over the ocean causes air to move from the land to the water as warm air rises and cold air from the land comes in to take its place (NIGHT time)

Local Winds

Local Winds Mountain Breezes and Valley Breezes occur in the same way as sea and land breezes