5 13. Polar Highs (90°N,S) - cold air sinks - Polar easterlies 14. Subpolar lows (60° N,S) - warm air rises in between ferrel cell and polar cell. - Polar jet can be observed near the tropopause Global Heat Imbalance: Primary energy input-> solar radiation (Results: Hot at equator, cold at poles) -> Zone of Low pressure at Tropics and High pressure at Poles. è Approximately 50% of the heat is transported by the atmosphere and 50% by the ocean. 15. Monsoon winds - Weak monsoon at the transition season (April to May) - Similar to the sea/land breeze system but on a seasonal time scale - Northern hemisphere winter: high pressure in northern India: North-east Monsoon o No monsoon in the atlantic and pacific, pacific has no land in north and south o High pressure systems move to the East o Onshore wind in Aus o ITCZ at the south - Northern hemisphere summer: low pressure in northern India: South-west Monsoon o High pressure systems move to the West o ITCZ at the north o Hadley and Ferrel cell converge at AUS o Offshore wind in Aus, WA is open to the Ferrel cell and experienced the westerlies.
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13. PolarHighs(90°N,S)
- coldairsinks -Polareasterlies
14. Subpolarlows(60°N,S)
- warmairrisesinbetweenferrelcellandpolarcell.
- Polarjetcanbeobservednearthetropopause
GlobalHeatImbalance:
Primaryenergyinput->solarradiation
(Results:Hotatequator,coldatpoles)
-> Zone of Low pressure at Tropics and High
pressureatPoles.
è Approximately50% of theheat is transported
bytheatmosphereand50%bytheocean.
15. Monsoonwinds
- Weakmonsoonatthetransitionseason(ApriltoMay)
- Similartothesea/landbreezesystembutonaseasonaltimescale
- Northernhemispherewinter: highpressureinnorthernIndia: North-eastMonsoon
o Nomonsoonintheatlanticandpacific,pacifichasnolandinnorthandsouth
o HighpressuresystemsmovetotheEast
o OnshorewindinAus
o ITCZatthesouth
- Northernhemispheresummer: lowpressureinnorthernIndia: South-westMonsoon
o HighpressuresystemsmovetotheWest
o ITCZatthenorth
o HadleyandFerrelcellconvergeatAUS
o OffshorewindinAus,WAisopentotheFerrelcellandexperiencedthewesterlies.
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Air-Seafluxesofheatandwater
è Seasurfacetemperatureandsalinityarecontrolledbyair-seainteraction.
è SeaSurfaceTemperature(SST)iswarm,SeaSurfaceSalinity(SSS)islow,excessprecipitation
canbeseenalongtheITCZ.
è SeaSurfaceTemperature(SST)iswarm,SeaSurfaceSalinity(SSS)ishigh,excessevaporation
canbeseenalongtheSubtropics.
HeatBudget:
Incoming short-wave radiant energy from the sun at the top of the atmosphere is balanced by
outgoinglong-waveradiation.(Incoming=Outgoing)
Air–Seaheatfluxes
Incomingshortwaveradiation(QSW)=
Outgoinglongwaveradiation(QLW)+Sensibleheatflux(QS)+Latentheatflux(QL)
Factorscontrollingthefluxes:
QSW–latitudeandcloudcover(albedo)*intheatmosphere*.=Qs
QLW–Temperature,watervapour,cloudcover.=Qb
QS–Boundarylayerturbulence,heatlostbyconduction(carriedbywind).=Qh
QL–Evaporation.=Qe
è QT=QSW-QLW-QS-QL
QSW–Lowheatfluxattheequatorduetotheabundanceofcloudcoverovertheseasurface;
QLW-highhumidityattheequatorwillreducetheheat;
QL–windspeedandrelativehumidityaffecttherateofevaporation;
QS–drivenbysurfacewindspeedandair-seatemperaturedifference.
ObliqueRays–Sumdirectlyoverhead in tropics.Rays strikesEarth surfaceat increasinglyobliqueangles.
ReflectionbyEarth–DifferentsurfaceshavedifferentAlbedoes.(Snow/Icereflects70-95%ofenergyreceived;water/forestreflects3-10%ofenergy)
Summer Solstice – length of the day is the longest, the amount of heat receives is different ascomparedtowintersolstice.
Lengthsofdayandnightvarymorebetweentheseasonsathigherlatitudes.Thismakesclimatemoreseasonalatthepolesthantheequator.
€
cPdTdt
=QIN −QOUT
9
Inertialmotion:circularpathduetocentrifugalacceleration=&'(
Centrifugalforcealwaysoperatesawayfromthecenter.
Centrifugalforce–outside;CoriolisForce–inside
ROTATION:NorthernH.–Clockwise;SouthernH.–anti-clockwise
CyclostrophicBalance:occurswhereflowisonasmallenoughscalewheretheCoriolisforcebecomesnegligible.
RossbyNumber:TheimportanceoftheCoriolisforceisdefinesthroughtheuseoftheRossbyNumber(Ro):
fRv
fvRv
ForceCoriolisForcelCentrifuga
Ro ===
2
..
SmallvaluesofRossbyNumber(Ro~0.01)–CoriolisForceisimportant(Geostrophicbalance)
LargevaluesofRossbyNumber(Ro>100)–CoriolisForceisNOTimportant(Cyclostrophicbalance)
Geostrophic Balance: If the pressure gradient term is known then can estimate the velocity. (Refer to
Geostrophicflowinthelatersection).
- Theonlyexternalforceisgravity.(Frictionisnegligible)
- Assumenoacceleration,steadystate,verticalvelocity<<horizontalvelocity(xandydirection).
18. Geopotentialsurface
- A geopotential surface is a horizontal surface i.e. gravity acts
perpendiculartoageopotentialsurface.UsuallydenotedbyФ.
- Velocity=0atthehorizontalsurface.
19. Barotropicflow(wellmixedocean)
- Whenisopycnals(linesofequaldensity)areparalleltoisobars.
- IfФisparalleltoisobarsthenthereisnomotion.
- Nodensitychange.
20. Baroclinicflow(Stratifiedocean)
- Windmovesthewaterwithoutchangingitsdensity.
- Paratrophicforce(wind&tides)
- Densityflow,densitychangeswithdepthandspace.
- Heating/coolingwillchangethetemperatureofthesystem
inturnschangingthedensityofthesystem(Baroclinicforce).
RossbyRadiusofDeformation()*)isthedistancethataparticleorwavetravelsbeforebeingsignificantlyaffectedbytheearth’srotation.ItdefinestheeffectofCoriolisforce.- Ldecreaseswithlatitude(increasingf)sothatawave(orcurrentforthatmatter)at
highlatitudeneedonlytravelashort distancebeforebeingaffectedbyCoriolisForce.
)* =+,-.
ℎ is the water depth.
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32b.NorthAtlanticSubtropicalGyre(SargassoSea)
- Surrounded by Gulf Stream, North Atlantic Current, Canary Current, and North Equatorial
Current.
33. CanaryCurrent- Awind-drivensurfacecurrentthatispartoftheNorthAtlanticSubtropicalGyre.
ThiseasternboundarycurrentbranchessouthfromtheNorthAtlanticCurrent andlaterjoinstheAtlanticNorthEquatorialCurrent.
34. BenguelaCurrent- Anorthwardflowingoceancurrentthatformstheeasternportionofthe - SouthAtlanticOceanGyre.AbranchoftheWestWindDriftoftheSouthernH.
35. CaliforniaCurrent- APacificOceancurrentthatmovesequatorward(southward)alongthe
westerncoastofNorthAmerica.Thiseasternboundarycurrentispartofthe NorthPacificSubtropicalGyre.
36. HumboltCurrent(PeruCurrent)- Acold,lowsalinityoceancurrentthatflowsequatorward(northward)along
thewestcoastofSouthAmerica.Aneasternboundarycurrent.
37. Upwelling/DownwellingintheOcean
- CoastalUpwelling(divergence)andDownwelling(convergence,duetogravitypullingwater
downwards).
- Themovements of watermass in the ocean are essential in stirring the ocean, delivering
oxygentodepth,disturbingheat,andbringingnutrientstothesurface.
- Downwelling:watergoesverticallydownwards. (occurs at horse latitude~30°N/S)
Majorcoastalupwellingecosystems
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