AtmosphericAtmospheric CirculationCirculation PatternsPatterns

Ally, Molly, JoeAtmosphere Jigsaw

Pre-assessment (T or F)Pre-assessment (T or F)

• Q: The atmospheric circulation moves only in vertical motion

• A: False, There are both vertical and horizontal motions in the atmospheric circulation

• Q: Air moves high pressure areas to lower pressure areas

• A: True

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WindWind• Created by air moving

from high pressure areas, to low-pressure areas, where air is less dense

• Horizontal winds follow curved trajectories due to the rotation of the earth

Sea BreezesSea Breezes• During day coastal land heats up more than the seaDuring day coastal land heats up more than the sea

– Air over land is thus warmed and rises, increasing pressureAir over land is thus warmed and rises, increasing pressure– Starts to cool and form cloudsStarts to cool and form clouds

• Air then flows from area of high pressure to lower Air then flows from area of high pressure to lower pressure over the sea. pressure over the sea.

• pressure at the surface is higher at seapressure at the surface is higher at sea– Air then flows in from the sea to the land Air then flows in from the sea to the land

• At night, when land cools more quickly than the At night, when land cools more quickly than the ocean, the cycle is reversedocean, the cycle is reversed

Coriolis ForceCoriolis Force• Cause winds that move over long

distances appear to curve – A force caused by Earth’s Rotation

• Different points on planet move at different speeds causing air to move faster in certain areas

• A parcel’s radius of spin around Earth decreases as it moves closer to Earth's axis of rotation– rate of spin increases

• The parcel will deflect to the right of its original trajectory due to its high angular velocity– In Southern hem. parcel would appear

to deflect left

Coriolis ForceCoriolis Force

• makes winds in low-pressure weather systems curve into spirals– Hurricanes

• As air travels, Coriolis force bends its course toward a state called geostrophic flow – pressure gradient force and Coriolis force

exactly balance each other

In the northern hemisphere…In the northern hemisphere…

High pressureHigh pressure region region develops pressure force develops pressure force directed away from the high. directed away from the high. • Air starting to move in response Air starting to move in response

to this force is deflected to the to this force is deflected to the right = clockwise circulation right = clockwise circulation pattern around a region of high pattern around a region of high pressure pressure

A A low-pressurelow-pressure region region develops, pressure forces air develops, pressure forces air from outside toward the low.from outside toward the low.• Air that moves because of the Air that moves because of the

force is deflected to the right force is deflected to the right and rotates counter-clockwise and rotates counter-clockwise around the system. around the system.

Air will spiral into low pressure areas near the Air will spiral into low pressure areas near the surface then rise once they reach the center.surface then rise once they reach the center.

As air rises, it cools, producing condensation, As air rises, it cools, producing condensation, clouds, and rain.clouds, and rain.

Air will spiral away from high pressure areas near Air will spiral away from high pressure areas near surface toward low pressure areas. surface toward low pressure areas. – To maintain barometric balance, air will descend from To maintain barometric balance, air will descend from

above. above.

When wind speed When wind speed declines…declines…

A general circulation of the atmosphere was presented in 1735 by English meteorologist George Hadley

Model shows warm air rising over the equator and sinking over the

poles simple circulation, upwelling near the equator and

descending in polar regions in reality circulation ends at a latitude of about 30°

air sinks to the ground and flows back to the tropics produces easterly winds near surface at low latitudes

and westerly winds at high latitudes Farther north and south, this pattern repeats in two

more sets of circulation zones between tropics and poles

Post-assessmentPost-assessment• Q: During the day air flows move _______ to _______, at

night it flows ______ to _______A) the sea to the land; the land to the seaB) the land to sea; the sea to the landA: A) the sea to the land; the land to the sea

• Q: Because of the Coriolis force, to which direction does air moving from lower to higher latitude deflect? (in Northern Hemisphere)A: to the right

• Q: High pressure produces ________ circulation pattern around the region, whereas low pressure produces _________ circulation pattern.A: Clockwise; Counterclockwise

• Q: Which pressure area will result in producing clouds and rain? High or low?A: Low pressure area

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