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Atmospheric and Oceanic Circulation AAtmtmosposphericheric aanndd OOceceananiicc CirculatCirculatioionn AtmoAtmossppherheriicc cciirrculationculation ttranransferssfers energenergyy andand massmass overover thethe EarthEarth . Redistributes surplulus energy alonlong the tropics to deficicitit areas . Generates weather patterns . Produces ocean currents . Spread naturall and anthropogenic pollllutiion WhatWhat isis aatmtmososppherhericic ppresressuresure?? AAttmospmospherihericc PresPressusurree AAirir prpressureessure –– prpressuressuree exexerertedted oonn thethe surfsurfaceace ofof thethe eartearthh byby thethe aatmosptmosphere.here. Motiion, siize and number of air moleculeles withiithin the atmosphere determiine the temperature and densityity of airir . Temperature and densitity of airir determine the pressure it exerts on the surface . Air pressure iis caused by the force of graviity pulllinling the mass of the atmosphere toward the surface of the earth WhatWhat dedetermterminineses aatmtmososppherhericic ppressressuurere?? AtmAtmoosspphheericric PPrressessuurree -Pressure = force per unit area -Due to gravity the atmosphere exerts a force AcAcccordingording toto ththee IdIdealeal GasGas LawLaw:: dendensisittyy ((ρρ)) andand temtemperaperaturturee (T)(T) cocontrolntrol atmoatmospherspheriicc pressupressurere ((PP)) PP == ρρRTRT RR == aa conconststanantt PressurPressure,e, DenDensisittyy && TemTemperaperatureture DensityDensity ((ρρ)) Amount of matter (mass) per unit volume (kg/m3) Densiity (of a gas) isis dirirectlly proportiionall to pressure Densiity varies withith alaltititude PressurPressure,e, DenDensisittyy && TemTemperaperatureture Temperature (T) Moleculeles move faster iin hot airir tthan cold airir Faster = more collillisions (more force) and therefore higher pressure Temperature is direirectlyly proportioional to pressure PressurPressure,e, DenDensisittyy && TemTemperaperatureture In the atmosphere densityity and temperature do not change inindependentlyly Examplele: When air inin the atmosphere isis heated iit expands and causes a decrease inin densitity and pressure HHooww iiss atatmomossphphericeric prepressssuurere mmeaeassuuredred?? AAtmtmospheosphericric PressurPressuree Atmosphericic pressure iis often measured iin miillillibars (mb) Atmosphericic pressure at sea lelevell isis 1013.25 millibibars (standard pressure) At the earth’s surface, pressure varies from 980 mb to 1030 mb (about 5%) AtmoAtmossppherheriicc PrPressureessure:: In 1643, a student of Galilileleo, Evangelilista Torricellilli develoloped a method for measuring airir prepressure whilile trying to drainin mines. Noticiced that water llevels wiithin miines varied dailyly . Arrivedived at the theory that the downward force of the atmosphere on the water surface also flluctuated →days of higigher air pressure caused lolower water lelevells witithinin mines MMeeasasururemementent ofof AAtmtmosospphehericric PrePressssurure:e: Atmosphericic pressure iis measured usiing and iinstrument calllled a barometer A mercuriall barometer measures atmospheric pressure wiith a colulumn of mercury Sea-levell pressure (1013mb) alslso can be definined as 29.92 ininches of mercury (in. Hg) AAttmospmospherihericc PresPressusurree A more common type of barometer isis the aneroid barometer It uses the pressure exerted agaiinst a partiall vacuum to measure airir pressure Note:Note: decrdecreaseease iinn airair ppressurressuree withwith iinnccrreaseease iinn elevatioelevationn - DecreaDecreasese boilingboiling pointpoint ooff waterwater - 0 m 100 C - 3000 m 90 C - 5000 m 80 C - IncrIncreaseease iinn cookingcooking timestimes atat higherhigher elevatelevationsions WWinindd WindWind –– horhoriizonzontaltal momovemenvementt ofof airair . Produced by differences iin air pressure from one lolocatiion to another . Air moves from locatiions of high pressure to locatiions of lolow pressure Measurement: wiind has two principipall components - Speed (anemometer) - Diirectiions (wiind vane) Wind Vane: -Points in the direction air is moving -Wind is named based on the direction from which it originated -Designated by compass directions ForcForceess DDrriviviningg AtmAtmososphpherericic MMotiotionon FFoourur forceforcess affectaffect thethe directdirectiioonn andand speedspeed ofof airair (wind)(wind) asas itit mmovesoves thrthrougoughouthout thethe atatmospmospherehere:: 3. GrGravitationavitationalal forcforcee 4. PressurPressuree ggradientradient forforcece 5. CoriolisCoriolis foforcerce 6. FFrrictioniction 1)1) GrGraviavitty:y: . Draws the mass of the atmosphere towards the surface of the earth . Causes decrease inin pressure and mass witith iincreasing elelevatiion . Wouldld not have an atmosphere or airir prpressure witithout iit 2)2) PressurPressuree GrGradientadient FFororce:ce: aaiirr momovesves frfromom hhiigghh prpressureessure reregionsgions toto lowlow prepressuressure . Variatioions in airir pressure are caused by uneven heatining of the earth’’s surface. UnevUnevenen heaheatingting ofof thethe eartearth’sh’s surfsurfaceace Warm surfaces encourage upward verticical motiion Upward airflow Converging Converging Horizontal Air Low pressure Horizontal Air area Warm S urface UnevUnevenen heaheatingting ofof thethe eartearth’sh’s surfsurfaceace As airir molecules cool,l, they condense and decend towards the surface Air Cools Diverging Diverging Horizontal Air High pressure Horizontal Air area LineLiness ofof eqequalual prpressuressuree areare isobarisobars:s: - b/c air moves from high to lolow pressure, the PGF isis exerted at 90º angleles from the iisobars - When isobars are cllose together the pressure gradieient isis higigher → stronger wininds - When isobars are farther apart the pressure gradieient is llower → weaker wininds 3)3) CoriolisCoriolis FFoorce:rce: airair flowflow iiss deflectedeflectedd frfromom aa straigstraightht patpathh byby thethe rotrotationation ooff thethe earearthth . Earth’s’s rotatioional speed iincreases from the poles toward the equator 0km /hr at the poles, 1675km /hr at equator Defllection iincreases north and south of the poles No deflectioion at the equator 3)3) CoriolisCoriolis FFoorce:rce: - TThehe earearthth rrotateotatess eaeassttwardward - Deflelectioion causes airir mmotioion to curve to the right inin the N Hem - Deflelectioion causes airir mmotioion to curve to the leftleft iin the S Hem GeoGeostropstrophichic WindWind –– upperupper levellevel windswinds tthathat mmoveove pparraarralllleell toto isolinesisolines b/b/cc thethe corioliscoriolis forforcece araree eqequalual . Rather than air fllowinging from higigh to low pressure, airir moves around higigh and llow pressure areas . Occurs witithinin upper lelevelsls of the troposphere NorthernNorthern HHeemmisispherpheree NorthernNorthern HemiHemispspheherere NorthernNorthern HemiHemispspheherere NorthernNorthern HemiHemispspheherere NorthernNorthern HemiHemispspheherere 4)4) FFrricicttionalional foforce:rce: dradragg (ba(backwckwaardrd forceforce)) onon wiwindnd asas itit movesmoves overover thethe earearth’sth’s sursurfaceface . Extends to and elevatioion of about 500m . Decreases witith inincreasining elevatioion . Varies withith surface texture, wiind speed, timeime of day/year, and atmos condititiions → Decreases speed of winind NorthernNorthern HemiHemispspheherere SummSummaryary ofof FFoorces:rces: GrGravityavity pullsls atmosphere toward earth creatiing airir pressure PGFPGF airir movesmoves from higigh to lolow pressure perpendicular to isisolinlines CoriolisCoriolis defllects winind dirirectiion due to earth’s rotatiion - zero at the equator - right iin N hem; left inin S Hem FFrrictioniction backward force on air movement sllowiing itit down High Pressure Low Pressure Anticyclone Cyclone NAME N Hem : cw circulation N Hem : ccw circulation CIRCULATION S Hem : ccw circulation S Hem : cw circulation Air spins out from Air spins in to center SPIN center VERTICAL Sinking Air Rising Air MOTION Surface divergence Surface convergence HORIZONTAL MOTION Upper-level Upper-level divergence convergence Clear skies, sunshine Clouds, precipitation WEATHER GGllobobalal AirAir PressPressureure PPaattertternsns:: TTeempermperatuaturere diffdiffereerencesnces alongalong thethe equaequatortor andand atat thethe polespoles causecause prepressuressure differdifferences:ences: . Pressure dififferences cause air to flolow . Warm airir alalong the equator rises creatiing llow pressure . Coldld, more dense air over the poles sininks creatiing higigh pressure . These pressure differences cause airir tto flolow from the poleles north and south to the equator . Thisis north-south air flolow iis calleled meridinall flow FFoourur primaprimaryry prpressureessure arareaseas foforr eaeachch hemhemisisppherhere:e: - EquatoEquatorialrial low-prlow-pressuressuree trtroughough (10(10 NN && S)S) - PolarPolar hhiiggh-prh-pressuressuree cellscells (9(900 NN && SS)) - SubtrSubtropicalopical high-high-prepressuressure ccellellss ((20-20-3535 NN && S)S) - SubpolarSubpolar low-prlow-pressuressuree cellscells ((6060 NN && SS)) - EquatoEquatorialrial low-prlow-pressuressuree trtroughough (10(10 NN && S)S) - Caused by inintense heatining of the earth’s surface - Warm airir risrises creatiing lolow pressure and associatediated weather - Characterized by warm, wet atmospheric conditioions - PolarPolar hhiiggh-prh-pressuressuree cellscells (9(900 NN && SS)) - SubtrSubtropicalopical high-high-prepressuressure ccellellss ((20-20-3535 NN && S)S) - SubpolarSubpolar low-prlow-pressuressuree cellscells ((6060 NN && SS)) - EquatoEquatorialrial
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