Ch. 12 Sec. 2 Weather Systems

Weather systems The earths rotation causes great weather effects The earths rotation causes great weather effects Coriolis Effect: Coriolis Effect: Air particles are deflected to the right in the Northern hemisphere & left in southern hemisphereAir particles are deflected to the right in the Northern hemisphere & left in southern hemisphere Creates global wind systems that transport airCreates global wind systems that transport air Balancing effectBalancing effect

Global Wind Systems 3 Zones/systems 3 Zones/systems Trade Winds: Trade Winds: 30 o N. & S. latitude30 o N. & S. latitude Air sinks and moves towards equator in westerly directionAir sinks and moves towards equator in westerly direction Air rises and back toward 30 o latitudeAir rises and back toward 30 o latitude Prevailing Westerlies: Prevailing Westerlies: 30 o - 60 o N. & S. latitudes30 o - 60 o N. & S. latitudes Eastern direction opposite of trade windsEastern direction opposite of trade winds

Global Wind Systems Polar Easterlies: Polar Easterlies: 60 o to poles60 o to poles Northeast to southwest in N. hemisphereNortheast to southwest in N. hemisphere Southeast to northwest in S. hemisphereSoutheast to northwest in S. hemisphere

Jet Streams Differences in temperature cause wind Differences in temperature cause wind Large temp. gradient in upper level results in a strong westerly wind Large temp. gradient in upper level results in a strong westerly wind Jet Stream: Jet Stream: Narrow bands of fast, high-alt. westerly windsNarrow bands of fast, high-alt. westerly winds Speeds up to – 12.2 km highSpeeds up to – 12.2 km high Polar jet stream separates polar easterlies from the prevailing westerliesPolar jet stream separates polar easterlies from the prevailing westerlies

Jet Streams Disturbances along jet streams cause large scale weather systems Disturbances along jet streams cause large scale weather systems Imbalances of bringing warm air to cold climate & vice versa cause the major weather changes Imbalances of bringing warm air to cold climate & vice versa cause the major weather changes

Fronts Mid altitude collision of different air masses Mid altitude collision of different air masses Front Front Narrow region separating two masses that are different densitiesNarrow region separating two masses that are different densities Temperature, pressure, humidityTemperature, pressure, humidity 4 main fronts4 main fronts

Cold Fronts Cold dense air displaces warm air along a steep front Cold dense air displaces warm air along a steep front Warm air rises: condenses & cools Warm air rises: condenses & cools Clouds, showers, & sometimes T-storms Clouds, showers, & sometimes T-storms

Warm Fronts Warm air displaces cold air Warm air displaces cold air Moves slower and experiences less friction and gives a gradual slope Moves slower and experiences less friction and gives a gradual slope Cloudiness and precipitation Cloudiness and precipitation

Warm & Cold

Stationary Fronts Air masses do not advance Air masses do not advance Seldom cloud formation and precipitation Seldom cloud formation and precipitation More like a warm front More like a warm front

Occluded Cold air moves rapidly overtaking the warm front & pushes it upwards & towards another cold front Cold air moves rapidly overtaking the warm front & pushes it upwards & towards another cold front Warm air squeezed between two air masses Warm air squeezed between two air masses Precipitation common Precipitation common

Pressure Systems Rising & Sinking air Rising & Sinking air Coriolis effect Coriolis effect Rotational pressure systems Rotational pressure systems High Pressure High Pressure Air sinks & and spreads away from center at Earth’s surfaceAir sinks & and spreads away from center at Earth’s surface Deflection of air caused by Coriolis effect causes clockwise rotationDeflection of air caused by Coriolis effect causes clockwise rotation

Pressure Systems Low Pressure Low Pressure Air rises being replaced from air outside systemAir rises being replaced from air outside system Spins inward towards center then upwardSpins inward towards center then upward CounterclockwiseCounterclockwise