atmospheric circulations prof. john toohey-morales, ccm st. thomas university miami gardens, florida

Atmospheric CirculationsAtmospheric Circulations

Prof. John Toohey-Morales, Prof. John Toohey-Morales, CCMCCM

St. Thomas UniversitySt. Thomas University

Miami Gardens, FloridaMiami Gardens, Florida

Scales of MotionScales of Motion

• Circulations exist in Circulations exist in all sizes within the all sizes within the atmosphereatmosphere

• MicroscaleMicroscale: Eddies a : Eddies a few meters or less few meters or less formed by formed by convection or by convection or by wind blowing past wind blowing past obstructions, lasting obstructions, lasting at most a few at most a few minutesminutes

Scales of Motion (continued)Scales of Motion (continued)

• MesoscaleMesoscale: : Circulation ranging Circulation ranging from a few from a few kilometers to about kilometers to about 100 km in diameter 100 km in diameter which can last which can last hours or a dayhours or a day– ThunderstormsThunderstorms– TornadosTornados– Local WindsLocal Winds

Scales of Motion (continued)Scales of Motion (continued)

• SynopticSynoptic: Weather : Weather map scale of map scale of hundreds or hundreds or thousands of thousands of kilometers, lasting kilometers, lasting days or weeksdays or weeks

Scales of Motion (question)Scales of Motion (question)

• An example of mesoscale motion isAn example of mesoscale motion isa. winds on a surface weather map of a. winds on a surface weather map of

North America.North America.

b. winds on a 500 mb chart.b. winds on a 500 mb chart.

c. winds blowing through a city.c. winds blowing through a city.

d. winds blowing past a chimney.d. winds blowing past a chimney.

e. the average wind patterns around the e. the average wind patterns around the world.world.

Local Wind Systems: Sea Local Wind Systems: Sea Breeze and Land BreezeBreeze and Land Breeze• A type of thermal, A type of thermal,

mesoscale mesoscale circulation setup by circulation setup by the uneven heating the uneven heating rates of land and rates of land and waterwater

• Leading edge is the Leading edge is the sea breeze front sea breeze front (Florida has 2), (Florida has 2), where in humid air where in humid air thunderstorms can thunderstorms can form to provide form to provide abundant rainsabundant rains

Local Wind Systems: Local Wind Systems: MonsoonMonsoon• Monsoon winds change direction seasonally, Monsoon winds change direction seasonally,

blowing from one direction in summer and the blowing from one direction in summer and the opposite direction in winteropposite direction in winter

• In India & SE Asia the Monsoon lasts from June to In India & SE Asia the Monsoon lasts from June to September and although it doesn’t rain every day, September and although it doesn’t rain every day, most of the year’s rainfall accumulates during that most of the year’s rainfall accumulates during that timetime

• Also seen in southwest USA in summer (AZ, NM, NV Also seen in southwest USA in summer (AZ, NM, NV & south CA)& south CA)

Local Wind Systems Local Wind Systems (questions)(questions)

• A sea breeze circulation is caused by A sea breeze circulation is caused by differences. differences.a. humiditya. humidity

b. temperatureb. temperature

c. altitudec. altitude

d. surface roughnessd. surface roughness

Local Wind Systems Local Wind Systems (questions)(questions)

• Surface low pressure becomes best Surface low pressure becomes best developed over the Asian continent developed over the Asian continent in thein thea. summer.a. summer.

b. winter.b. winter.

c. fall.c. fall.

d. spring.d. spring.

Global WindsGlobal Winds• Earth’s general Earth’s general

circulation is driven circulation is driven by unequal heating by unequal heating of the surface, with of the surface, with warm air transported warm air transported poleward and cool poleward and cool air equatorwardair equatorward

• The The Hadley CellHadley Cell is is the simplest the simplest theoretical form to theoretical form to visualize the global visualize the global circulationcirculation

Three-Cell Model of Three-Cell Model of CirculationCirculation• More realistic More realistic

depiction of the depiction of the general general circulationcirculation

• Three cells per Three cells per hemisphere have hemisphere have the task of the task of energy energy redistributionredistribution

Go to Visualization

Prevailing WindsPrevailing Winds

• DoldrumsDoldrums are near the equator where are near the equator where the air is warm, PGF is weak, and winds the air is warm, PGF is weak, and winds are light. In the vertical the air is rising. are light. In the vertical the air is rising.

• Trade WindsTrade Winds blow at the surface in the blow at the surface in the tropics and subtropics toward the low tropics and subtropics toward the low near the equator. Where they meet near the equator. Where they meet they form the they form the Intertropical Intertropical Convergence Zone (ITCZ)Convergence Zone (ITCZ)

Prevailing Winds Prevailing Winds (continued)(continued)

• Poleward at 30° latitude you find the Poleward at 30° latitude you find the horse latitudeshorse latitudes with light winds under with light winds under subtropical highsubtropical high pressure, where air pressure, where air descends in the vertical after arriving descends in the vertical after arriving from the equator on the Hadley Cellfrom the equator on the Hadley Cell

• The descending air diverges, part of The descending air diverges, part of it heading poleward but deflected by it heading poleward but deflected by Coriolis to form the Coriolis to form the westerlieswesterlies

Prevailing Winds Prevailing Winds (continued)(continued)

• Surface air moving away from the Surface air moving away from the poles out and under the poles out and under the polar highpolar high meets the westerlies at the meets the westerlies at the polar polar frontfront near 60° latitude, where air near 60° latitude, where air rises and storms develop on the rises and storms develop on the subpolar lowsubpolar low. The rising air diverges . The rising air diverges aloft, either into the aloft, either into the Polar CellPolar Cell or the or the Ferrel CellFerrel Cell

Prevailing Winds (questions)Prevailing Winds (questions)

• Chicago, Illinois (latitude 42o N) is Chicago, Illinois (latitude 42o N) is located in thelocated in thea. northeast trades.a. northeast trades.

b. southeast trades.b. southeast trades.

c. westerlies.c. westerlies.

d. doldrums.d. doldrums.


• Chicago, Illinois (latitude 42° N) is Chicago, Illinois (latitude 42° N) is located in thelocated in thea. northeast trades.a. northeast trades.

b. southeast trades.b. southeast trades.

c. westerlies.c. westerlies.

d. doldrums.d. doldrums.


• At Barrow, Alaska (latitude 70o N), At Barrow, Alaska (latitude 70o N), you would expect the prevailing wind you would expect the prevailing wind to beto bea. northerly.a. northerly.

b. easterly.b. easterly.

c. southerly.c. southerly.

d. westerly.d. westerly.


• At Barrow, Alaska (latitude 70° N), At Barrow, Alaska (latitude 70° N), you would expect the prevailing wind you would expect the prevailing wind to beto bea. northerly.a. northerly.

b. easterly.b. easterly.

c. southerly.c. southerly.

d. westerly.d. westerly.


• Generally, along the polar front one Generally, along the polar front one would would notnot expect to observe expect to observea. temperatures on one side lower than a. temperatures on one side lower than

on the other side.on the other side.

b. an elongated region of lower pressure.b. an elongated region of lower pressure.

c. clouds and precipitation.c. clouds and precipitation.

d. converging surface air.d. converging surface air.

e. sinking air aloft.e. sinking air aloft.


• On a weather map of the Northern On a weather map of the Northern Hemisphere, one would observe the Hemisphere, one would observe the westerlieswesterliesa. north of the subpolar lows.a. north of the subpolar lows.b. south of the tropical highs.b. south of the tropical highs.c. between the doldrums and the horse c. between the doldrums and the horse

latitudes.latitudes.d. between the subpolar lows and the d. between the subpolar lows and the

subtropical highs.subtropical highs.


• In terms of the three-cell general In terms of the three-cell general circulation model, the driest regions circulation model, the driest regions of the earth should be nearof the earth should be neara. the equator and the polar regions.a. the equator and the polar regions.b. the equator and 30° latitude.b. the equator and 30° latitude.c. the equator and 60° latitude.c. the equator and 60° latitude.d. 30d. 30° ° latitude and 60latitude and 60°° latitude. latitude.e. 30° latitude and the polar regions.e. 30° latitude and the polar regions.


• The "roaring 40s" are strong surface The "roaring 40s" are strong surface winds found near 40°S latitude. winds found near 40°S latitude. Would these be EASTERLY or Would these be EASTERLY or WESTERLY winds? (circle one WESTERLY winds? (circle one answer)answer)


• The "roaring 40s" are strong surface The "roaring 40s" are strong surface winds found near 40°S latitude. winds found near 40°S latitude. Would these be EASTERLY or Would these be EASTERLY or WESTERLYWESTERLY winds? (circle one winds? (circle one answer)answer)

Semi Permanent Highs & Semi Permanent Highs & LowsLows• The general 3-cell circulation results in high The general 3-cell circulation results in high

pressure at the poles and at 30° latitude, while pressure at the poles and at 30° latitude, while low pressure is seen at the equator and 60° lat.low pressure is seen at the equator and 60° lat.

• These shift slightly with the seasons, north in These shift slightly with the seasons, north in summer and south in wintersummer and south in winter

Semi Permanent Highs & Semi Permanent Highs & LowsLows• Notable highs include the Notable highs include the Bermuda HighBermuda High and and Pacific Pacific

HighHigh• Notable lows include the Notable lows include the Aleutian LowAleutian Low and the and the

Icelandic LowIcelandic Low• The The Siberian HighSiberian High is a seasonal high, while the is a seasonal high, while the

monsoon is an example of a seasonal monsoon is an example of a seasonal thermal lowthermal low

Common Precipitation Common Precipitation PatternsPatterns• Areas of high Areas of high

precipitation exist in the precipitation exist in the tropics near the ITCZ as tropics near the ITCZ as well as between 40° & well as between 40° & 60° latitude where low 60° latitude where low pressure and the polar pressure and the polar front force air upwardsfront force air upwards

• Deserts can be found Deserts can be found near 30° latitude and at near 30° latitude and at the poles with subsiding the poles with subsiding dry air related to high dry air related to high pressurepressure

Highs Surrounding the U.S.Highs Surrounding the U.S.• The position of the Pacific High plays a crucial role The position of the Pacific High plays a crucial role

in determining the precipitation pattern of in determining the precipitation pattern of California and the Pacific NorthwestCalifornia and the Pacific Northwest

• The Bermuda High provides for fair weather, except The Bermuda High provides for fair weather, except where it pumps moisture from the Caribbean and where it pumps moisture from the Caribbean and Gulf of Mexico into the eastern United StatesGulf of Mexico into the eastern United States

Highs Surrounding the U.S. Highs Surrounding the U.S. (question)(question)

• The Pacific high moves NORTH The Pacific high moves NORTH SOUTH in the summer. Because of SOUTH in the summer. Because of RISING SINKING air along its eastern RISING SINKING air along its eastern side, relatively DRY WET conditions side, relatively DRY WET conditions prevail along the California coast. prevail along the California coast. (choose one word from each pair) (choose one word from each pair)

Highs Surrounding the U.S. Highs Surrounding the U.S. (question)(question)

• The Pacific high moves The Pacific high moves NORTHNORTH SOUTH in the summer. Because of SOUTH in the summer. Because of RISING RISING SINKINGSINKING air along its eastern air along its eastern side, relatively side, relatively DRYDRY WET conditions WET conditions prevail along the California coast. prevail along the California coast. (choose one word from each pair) (choose one word from each pair)

Jet StreamsJet Streams• Found at the tropo-Found at the tropo-

pause between 33K pause between 33K and 46K feet highand 46K feet high

• Are less than 1 mile Are less than 1 mile thick with winds thick with winds sometimes sometimes exceeding 100 mphexceeding 100 mph

• Situated where there Situated where there are great are great temperature temperature contrasts, like at the contrasts, like at the polar frontpolar front

Go to Visualization

• Polar jet moves S in Polar jet moves S in winter and N in winter and N in summersummer

• Isotachs are lines of Isotachs are lines of equal wind speed equal wind speed and aid in locating and aid in locating jet streamsjet streams

Jet Streams (question)Jet Streams (question)

• In the Northern Hemisphere, the polar jet stream In the Northern Hemisphere, the polar jet stream is strongest whenis strongest when

a. air north of the polar front is much colder than a. air north of the polar front is much colder than air south of the polar front.air south of the polar front.b. air north of the polar front is much warmer b. air north of the polar front is much warmer than air south of the polar front.than air south of the polar front.c. air temperatures on opposite sides of the polar c. air temperatures on opposite sides of the polar front are about equal.front are about equal.d. air temperatures on the East Coast of the US d. air temperatures on the East Coast of the US are much colder than on the West Coastare much colder than on the West Coast

of the US.of the US.

Important Ocean CurrentsImportant Ocean Currents

• Currents are started by friction from the Currents are started by friction from the windswinds

• 40% of heat transport from the tropics to 40% of heat transport from the tropics to the poles comes solely from ocean currentsthe poles comes solely from ocean currents

• Gulf Stream moves up the eastern U.S. Gulf Stream moves up the eastern U.S. coast and on to northern Europe via the coast and on to northern Europe via the North Atlantic DriftNorth Atlantic Drift

• California Current carries cool water south California Current carries cool water south along the west coast of the U.S.along the west coast of the U.S.

El Niño / Southern El Niño / Southern OscillationOscillation• Southern Oscillation is the breakdown of the typical Southern Oscillation is the breakdown of the typical

pressure patterns at opposite ends of the Pacific pressure patterns at opposite ends of the Pacific which leads to weaker E to W trade windswhich leads to weaker E to W trade winds

• Leads to El Niño, with warm tropical western Pacific Leads to El Niño, with warm tropical western Pacific water spreading east towards the South American water spreading east towards the South American coastcoast

El Niño / Southern Oscillation El Niño / Southern Oscillation (continued)(continued)• El Niño occurs at irregular intervals every El Niño occurs at irregular intervals every

2 to 7 years, differing both in strength and 2 to 7 years, differing both in strength and behaviorbehavior

• Opposite condition known as La NiñaOpposite condition known as La Niña

ENSO ConsequencesENSO Consequences• Additional warmth & Additional warmth &

moisture leads to heavy moisture leads to heavy rain and floods in rain and floods in Ecuador & Perú, as well Ecuador & Perú, as well as more hurricanes and as more hurricanes and typhoons in the eastern typhoons in the eastern and central Pacific and central Pacific OceanOcean

• Other areas like Other areas like Indonesia, South Africa Indonesia, South Africa & Australia experience & Australia experience drought, and the drought, and the Atlantic sees less Atlantic sees less hurricaneshurricanes

• California and the Gulf California and the Gulf Coast sees heavy rain Coast sees heavy rain with the enhanced with the enhanced subtropical jet streamsubtropical jet stream

ENSO Consequences (cont.)ENSO Consequences (cont.)• Total worldwide damage can exceed $8 billionTotal worldwide damage can exceed $8 billion• Better forecasting of ENSO could come from Better forecasting of ENSO could come from

extensive studies of the phenomenon since 1985extensive studies of the phenomenon since 1985

atmospheric circulations prof. john toohey-morales, ccm st. thomas university miami gardens, florida

Documents

global circulation slide

global winds

light winds

surface roughness slide

sea breeze circulation

florida slide

monsoon monsoon winds

minutes slide