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OceanographyClimatologyTopics under OceanographyOcean bottom relief

petroleumSulphurResources from continental shelf

Placer depositPearls, fish, calciumResources from continental shelf

Continental slopeContinental riseContinental margins

Poly-metallic nodulesIndian explorationAbyssal plain

Continental IslandsVolcanic islandsTypes of Islands

Sand-bar islandsCoral IslandsTypes of Islands

formationSymbiotic relationship between coral polyps and xooxanthalae

Sunlight depth 50 mTemp 25-27 degSalinity 33Calm, circulating nutrient rich waterNot at mouth of riverconditionsCoral reefCoral bleachingCoral polyps expel xooxanthalae under stress condition

Global warmingOzone depletionOcean acidificationSedimentationMarine pollutiondiseasesReasons for bleachingCoral reefFringing reef barrier reef- atollSubsidence theory of DarwinStandstill theory of MurrayFormation of coral reef

Motion of Ocean waterwaves

Ocean currentsHorizontal motion of ocean water

tidesSpring-neap tideTides

Upwelling

Down-wellingUp-welling and down-welling

Main energy source - InsolationOceans play important role in energy and temperature regulation on earth, due to specific heat of the waterAverage temperature of ocean = 3-5 degree CelsiusBut average surface temperature of ocean water = 25 degree

Temperature of Ocean

Latitudinal variationIt decreases from equator to polesBut highest temperature is not at the equator but at the tropicsReason: high rainfall, cloud cover (high albedo/ reflection of sunrays)

Temperature Pattern of the OceanHemispheric variationNorthern hemisphere warmer than southernReason: large land mass in northern hemisphere high energy

Temperature pattern of the OceansEnclosed seasMarginal seas of tropics warmer than open Ocean + marginal seas of temperate region cooler than open seasReason: less mixing of water

Temperature pattern of the OceansOcean currentsWarm ocean current warming effectCold ocean current cooling effectTemperature pattern of the Oceans

Up-welling and dow-wellingUpwelling bring cool water from depth lower down the surface tempTemperature pattern of the Oceans

Down-welling piling up of warm water increase the tempTemperature pattern of the Oceans

Max temp of day and min temp of night timeTropical water higher diurnal range than equatorial watersBecause, Heating and cooling of water rapid under clear skyDiurnal range of temperature

Bigger the size of ocean- better mixing of water and heatLower annual rangePacific ocean lower annual range than Atlantic OceanAnnual range of temperature Prelims 2007Q. Consider the following statements:Annual range of temperature is greater in Pacific ocean than in Atlantic oceanAnnual range of temperature is greater in northern hemisphere that in southern hemisphereUPSCQuestion Prelims 2007Which of the statement is correct?a) 1 onlyb) 2 onlyc) Both 1 and 2d) Neither 1 or 2

Ans. B) Pacific Ocean better mixingUPSCQuestion1st layer upto 500m(20-25 deg C)2nd layer thermocline 500-1000m 3th layer cold layer beyond 1000m

Vertical distribution of temperature

Temp decreases with increasing depth rate of decrement is rapid at equator tropics than towards poles1st layer permanent in Tropics temperate only in summer

Vertical distribution of temperatureAmount of salt found in 1000 gm of waterNacl (78%), MgCl2 (11%), MgSO4 (3.5%), CaSO4 (2.5%)Na and Cl has high residual time in ocean water very gradual removal thats why, they remain in the highest proportion

Salinity of Ocean waterIrrespective of absolute salinity of the water, the proportion of the salt remain same in all parts of the oceansAmount of addition or extraction of fresh water compared to salt content in the Ocean water decides absolute salinity of the Oceans.

Salt BudgetSediments carried by riversSubmarine volcanism at MORChemical reaction between rocks of geothermal vent of volcano and cold waterErosion of oceanic rocks

Sources of salts in ocean waterPhysical removal waves break at the beaches, salt-sprayBiological removal marine life forms extract calcium from sea water for their bones

Removal of Salts in Ocean waterAddition of fresh water => Rainfall, inflow of large river, melting of glacier => less salinityReduction of fresh water => increase in temperature, high evaporation, windy (wind accelerate the evaporation)

Variation in salinityStandard salinity of ocean water is = 35.5 ppt salinity of Atlantic OceanDead Sea (350 salinity), Lake van (400), Lake Urmia Man seldom drowned in sea with high salinityBecause, high salinity = high density

Salinity of the oceans

Salinity goes decrease from equator to polesBut highest salinity is not at the equator = because high rainfall, cloud coverHighest salinity is at tropics

Pattern in variation of salinity

Northern hemisphere warmer high evaporation salineBut in southern Pacific- roaring 40, furious 50 and shrinking 60 screaming 70 very fast winds High evaporation => high salinity

Pattern in variation of salinity1st - Ocean currentswarm ocean current like, high evaporationCold current led to Up-welling: cooler water from depth come at the surface => low salinity

Local Variations in Salinity2nd - Enclosed seas low latitude - warmer than open sea- high salinityEx. Mediterranean Sea, Red sea high latitude- cooler than open sea low salinityEx. Baltic Sea

Local Variations in Salinity3th inflow of large rivers Ganga Brahmaputra flow into Bay of BengalBay of Bengal less saline than Arabian sea

Local Variations in Salinity

Mississippi in G.of Mexico

Amu darya, Syr darya to Aral seaRivers inflow to the seasBlack sea

Persian gulfRivers inflow to the seas

4th glaciersBaltic sea receive fresh water from melting of glaciers low salinity

Local Variations in SalinitySalinity decreases with increasing depthTemp of water decreases Density of water increasesSalinity increases density water sinksSaline water freeze slowly compared to pure waterVertical pattern of salinityEquator salinity increases with depth upto some layer than decreases with depthBeyond equator salinity decreases with depthVertical salinity variation of oceans is complicated No uniform layering Vertical pattern of salinityTemperature of ocean watervariationsSalinity of ocean waterSalt budgetvariationsClimatology

Early atmosphere has H and He in abundance -lighter gases escapedDuring early life of the earth extensive volcanism- degassing. N, S, Water Vapour, Argon and CO2 came out

Origin of the Atmosphere on Earth

Water vapour condensed clouds rainfall washed out bulk of the CO2 into Oceans. Co2 = 0.03%Oxygen from anaerobic respiration of bacteria like, Cynobacteria

Origin of the Atmosphere on EarthGasProportionNitrogen78%Oxygen21%Argon0.93%Carbon dioxide0.03%Neon0.0018%Helium0.00005%ozone0.00006%Proportion of gasesN, O, H and Argon are permanent gasesWater vapour, Co2, ozone -> variable gases, GHGN, Argon inert gases Atmospheric gases- no chemical interaction among themThey dont lose their propertiesThey act as a single unified gas

Proportion of gasesStructure of atmosphere

90% of atmosphere within 32 kmTropopause = Height 8 km at poles, 18 km at equatorAt equator cumulonimbus clouds

Troposphere

Temperature decrease as height increasesTransparent to insolation (shortwave)Heated by terrestrial radiation (longwave)GHGs absorbs long wave terrestrial radiation

Greenhouse effect in tropospherePrelims2012Q. normally, the temperature decreases with increase in height from the earths surface, because,Atmosphere can be heated upward only from earths surfaceThere is more moisture in upper atmosphereThe air is less dense in upper atmosphereUPSCQuestionPrelims20121 only2 and 31 and 31,2 and 3

Ans. C)Less dense = less amount of GHGs = low tempUPSCQuestionTemperature increases with heightBecause of the presence of ozone layerOzone absorbs UV rays from isolationstratosphere

Prelims2011Q. The jet aircrafts fly very easily and smoothly in lower stratosphere. Why?There are no clouds or water vapour in lower stratosphereThere are no vertical winds in lower stratosphere

Ans. 1 in wrong, 2 is correctUPSCQuestion

Absence of GHGsTemperature decreases with height

MesosphereMesospheric cloudsClouds visible at high latitudesDuring summer season Condensation of mixture of meteoric dust and some moisture

Noctilucent clouds

Temperature increase with heightGases in ionic state trap insolation extremely hotBut ions are highly dispersedUp to 800 km from earthThermosphereFrom 80km to 640 kmNumber of ionic layersUseful in radio-communication

Ionosphere

High energy sunrays and cosmic rays break the atoms of air molecules become ionised (+ve charged)Behave as free particlesAt night time, only cosmic rays ionization -weak

Ionosphere

layersheightFrequencyPresenceformationD60-90kmLFDay-timeSolar radiationE99-130kmMF, HFDay-timeUV with N moleculeF150-380kmMF, HFDay &nightG>400kmMF, HFDay & nightLayers of IonospherePrelims2011Q. A layer in Earths atmosphere called ionosphere facilitates radio communication. Why?Presence of ozone cause reflection of radio waves to earthRadio waves has long wavelength

Both statements are wrong UPSCQuestion

Beyond 640 kmHighly rarified atmosphereVery high temperature- but different from air temperature- because no existence of air- temp cant be feltExosphere

Glowing lights at mid-nights at high latitudesAt height of exosphere and magnetosphereAurorasun emit solar wind/storm from its coronaSolar wind consist of plasma (free electrons and +ve ions)Interaction of solar wind with earths magnetosphere -disturbanceAurora

Collision of charged particles (isonization) in magnetosphereIonised particles emit light release energycharged particles interact with geomagnetic field linesThus, visible on high latitudesAuroras

The average temperature of the earth 15 degreeEarth maintains influx and out-flux of the energy, but out-flux is not immediate, it has long time gap. That is why, the temperature is maintained.

Heat budget

First 35% absorbed by Ozone layerThen 15% by cloud coverOnly 50% energy reached to the earth surface

Heat budget - Incoming20% is lost in latent heat of evaporation 10% lost in sensible heat (temperature of the body) 15% absorbed by GHGsRemaining 5% was released in the space

Heat budget - outgoing

Ratio between the total solar radiation falling upon a surface and the amount reflectedRepresents as %Earths avg. Albedo = 35%Lowest- dark soil highest - snowfall AlbedosurfaceAlbedoFresh snow80%-90%Desert35-45%Grasses26%Crops15%Brick - concrete10-20%Albedo - tablePrelims2010Q. Which one of the following reflect back more sunlight as compared to other three?sandy desertPaddy cropsLand covered with fresh snowPrairie land

Ans. C)

UPSCQuestionHorizontalwhen there is pressure gradient from high pressure to low pressure => advection

when air get warm, gets expands, becomes lighter => move upwards => convection

verticalMovement of air

When air gets hotter than surrounding air, it rises upwardIf it has moisture - latent heat of condensation more heated will go up - form clouds -can bring rainfall = instability

Vertical movement of air - instability

When air is cooler than surrounding it cannot move upward sinking air atmospheric stability or anti-cyclonic conditionHigh pressure on groundVertical movement of air - stabilityLow pressure High pressure

The rate at which air packet cools while risingAvg adiabatic lapse rate is 6.4 degree/kmThat is air packet gets cool by 6.4 degree after covering one km upward

Adiabatic lapse rate

if air packet has high moisture content- not get cool so fast. Its adiabatic lapse rate WALRWet air can reach higher distances with low lapse rate => create instability

Wet adiabatic lapse rate

If air packet is dry, it does not have much moisture, it will get cool very fast. More than 6.4 degree/km like, 10 degree/km. Dry air create stable condition

Dry Adiabatic Lapse rate

situationconditionConditional stability

when wet ALR< normal ALR < dry ALRAbsolute stabilitywhen normal ALR< wet ALR < Dry ALR

Absolute instability

when wet ALR< Dry ALR< normal ALRConditions of stability and Instability

Normally, with increasing height temperature of air decreasing, but reverse is happened than it is called temperature inversion

Temperature Inversion1st At Tropopause temperature starts increasing from hereSo air packet reach till here, start moving downwards

Ex. Of temperature Inversion

2nd A cool winter night, the air above the cold surface gets cool. But the air layer above that cool layer is till warmer. Then, by going upward, air does not get cooler but warmer Ex. Of temperature Inversion

3thValley inversionwinter cool air descends to valleyUplift the warm air of valleyDescending cool air- damage crops- frostEx. Of temperature Inversion

Formation of fogWarm air cooled by cold air below condensation tiny water droplets- low visibilityFormation of frost Water moisture frozen with contact cold surface- damage to cropsAtmospheric stabilityPrevents upward or downward movement of air- Discourage rainfallImplications of temperature inversionmains2013Q. What do you understand by phenomenon of temperature inversion in meteorology? How does it affect weather and habitants of the place? (5)

UPSCQuestionCondensation of water dropletResultAt heightsCloudsAt lower levelFogon the cold surfaceDew dropTurn into ice crystal in extreme cold conditionsFrostCondensation of water droplets AdvectionMoving of warm air over coldRadiationWinter nights loss of heat due to terrestial radiation cold surface. Moving of warm air over cold surfaceOcean currentMeeting of cold and warm ocean currentsReason for formation of fogDecreasing level of visibilityfogWater droplet condensed around a dust particleIt reduces the visibility, damage the cropsWater droplet condensed around a particle of pollutant, like SO2Reduce visibility + health hazard

smogcomparisonSmogIt occurs in warm, dry and sunny climateMixture unsaturated hydrocarbons and nitrogen oxides (NO2) in presence of sunlightIts components are ozone, nitric oxide, acrolein, and formaldehyde and peroxyacetyl nitrate (PAN).Photochemical smogcomparisonIt occurs in cool humid climateIt is a mixture of smoke, fog and sulphur dioxide (SO2).

Prelims2013Q. Photochemical smog is resultant of reaction amongNO2, O3 and peroxyacetyl nitrate in the presence of sunlightCO2, O2 and peroxyacetyl nitrate in the presence of sunlightCO,CO2 and NO2 at low temperatureHigh concentration of NO2, O3 and CO in the eveningUPSCQuestionPrelims2013Photochemical smog:NO2, Ozone + sunlight

Ans. A)

UPSCQuestionStructure of atmosphereVertical Movement of airAdiabatic lapse rateTemperature inversion and its effectsfogprecipitation

1) High temperature2) LP conditions3) Fast moving windWater vapour evaporate from the water bodyEvaporation adds moisture in the airEvaporation Absolute HumidityWeight of water vapour in unit volume of moist airWeight of water vapour per unit weight of dry airSpecific HumidityHumidityPrecipitation when air is saturated with water vapour and any extra addition result in precipitationRelative Humidity:Amount of water vapour present in air to amount of water vapour required for saturation

Precipitation depends upon temperature and moisture content of the airHot air saturation reach with more moisture content than cold air

Precipitation

Types of cloudsConvectional rainfall

Orographic rainfallTypes of rainfallCyclonic rainfall

Frontal rainfallTypes of rainfallEntire earth is divided into 4 large pressure beltsIn reality, belts are not continuous but pockets of low and high pressure. But pressure can be created through thermal or dynamic reasonsThermal: high temperature=> LP, low temperature => HPDynamic: air rises => LP, air descends => HP

Pressure system of the world4 belts:equatorial low pressure beltsub-tropical high pressure belt sub-polar low pressure beltPolar High pressure area

Pressure system of the world

Equatorial LP beltConstant insolationAir gets warm -LPAir move upward -> cloud formation -> instability -> rain in the evening dailyCumulonimbus cloudsConvectional rainfall

Equatorial LP beltAbsence of advection of airBelt of calm / DoldrumBecause light, feeble winds - calm region

The air above equator move towards pole, but coriolis force - their path get deflected. The length of path increases. Their energy reduced in mid-path -cooled. air subside near 30-40 deg latitude.

Sub-tropical HP belt (STHP)

As descending air HPDynamically induced HPCalled horse latitude

Sub-tropical HP belt (STHP)

From the pole, cold winds move towards equatorThe both warm and cold winds collide, the warmer winds from STHP rise above the cold polar windsThis rising of warmer wind near 50-60 degree create LP

Sub-polar LP belt (SPLP)

Air risen at SPLP, descends at polesHigh pressure conditionsThermally inducedPolar high

Wind system of the worldwinds blowing at the same direction throughout the yearcover large distances.Horizontal movement, Pressure belt system provide them the pressure gradientCorilis force modify their direction

Planetary winds

The winds move towards equatorial low pressure = ITCZITCZ inter tropical convergence zone, where wind convergesTheir direction is east to west due to coriolis force

Trade winds

Tropical easterlies flows east to westWind becomes dry when they reaches the western coast of the continentsOff shore trade windsTrade wind deserts Tropical deserts and trade winds

2ndCold currents provide desiccating effect to trade wind desertsCold current flow on western margins of continents Tropical desert and cold currentsMains2013Q. Major hot deserts in northern hemisphere are located between 20-30 degree North latitudes and on the western side of the continents. Why? (10) UPSCQuestionFrom west to eastFrom STHP to SPLPWesterlies

From west to eastFrom STHP to SPLPLess landmass in southern hemisphereFast flowing winds in the open sea Roaring 40s, furious 50s, shrinking 60s and screaming 70s

WesterliesPrelims2011Q. Westerlies in southern hemisphere are stronger and persistent than northern hemisphere. Why?Southern hemisphere has less landmass as compared to northern hemisphereCoriolis force is higher in southern hemisphere as compared to northern hemisphereAns. 1 is correct, 2 is wrongUPSCQuestionFrom east to westFrom poles to SPLP

Polar Easterlies

SummerWinterApparent movement of the sun

Summer

Wintermovement of the pressure systemWind system of the worldMonsoon winds: seasonal reversal of windsFeature of tropical latitudeIn winter trade wind blows north to south, in summer trade wind blows south to north [but in limited area]

Seasonal windsDue to apparent northward movement of the sun in summer. Thus, the ITCZ (LP) also moves upwardThus, the area which was under northern trade winds in winter, will come under southern trade winds in the summer

Monson winds

Wind system of the worldCold windcountrywindGreeceGragaleItalyTremontaAdriatic seaboraMountainsWindAlpsFohnRockiesChinookAndesZondaWarm windsLocal winds : mountains windsCold wind: landHP condition in winterDivergence of cold airSiberia BuranCanada - BlizzarddesertWindsSaharaSiroccoEgyptKhamsinLibyaGibliGulf of GuineaHarmattanWarm wind: desertLocal winds : landsummerHot-dusty wind = loostatesWindBihar, WB, AssamKalbaishakhiKNBlossom showerKRMango showerPre-monsoon thunderstormLocal winds: India Wind system of the worldDuring night time: top gets cooler than valley = HP, valley =LPWind move hill-top to valley => mountain breezeAgriculture frost bite, chill in habitation in the valley

Mountain breeze

During day time: top gets warmer than valley = LP, valley = HPSo wind moves from valley to the top => valley breeze

Valley breeze

Wind system of the world

Land breezesDifferential cooling of land and waterDuring night: land cooler =HP, water =LPWind move land to water => land breeze

Sea-breezeDuring day time: land gets warmer =>LP , water =HPWind move from water to land => sea breeze

Pressure belts of the worldPlanetary wind systemVariable windsSeasonal, local windsMountain- valley breezeLand-sea breeze

Around tropopause, there is only one gradientWind accumulated above equator and rarified atmosphere above polesHP at the equator and LP at the poles

Upper tropospheric windsstrong coriolis force at tropopauseBecause friction is less - high speed - stronger the coriolis forceSo the deflection is 90 degreeSuch winds called geo-strophic windsGeo-strophic winds

Westerlies windsThe upper tropospheric winds / geo-strophic winds blow from west to east at the very high speed

Westerlies at poles to maintain the angular momentum- they meander => Rossby wavesRossby waves do not meander consistently, but follow a cycle = Index cycle

Rossby wavesIn westerlies, there are strong, narrow bands of high speed wind => Jet streamSpeed of Jet stream 300kmph

Jet streams

There are situated at the margins of meridional cells4 permanent Jet streams: 2 Polar Jet and 2 Sub-Tropical Westerly Jet STWJ

Jet streams location

Permanent jet stream

Temporary jet streamJet streamsJet stream embedded in westerlies (Rossby waves) at high latitude, cause pressure variabilityThats why they are called travelling depressionJet streams

Jet Stream travelling depressionsWeather of higher latitude is more complex than weather of equatorial or tropical regionsBecause tropical and equatorial region are heat surplus region thermal reasons play the dominant role. But higher latitude are heat deficit region dynamic reasons play dominant roleThese include localised + upper-tropospheric circulations (Rossby waves, Jet streams, temperate cyclones)

Weather of Mid and high latitude

Large extensive body of air-mass (1000sqkm)Height upto TropopauseAt particular height, one air mass will have uniform temperature and moisture across its widthAirmasses can be differentiate according to their temperature and moisture content

Air mass

Air mass acquired properties from the source regions land, marine, polar, arctic, Antarctic = give them identity. Ex. mP, cTExtensive homogeneous surface + longer stay (HP)

Air massAir masses do not stay at their source regions forever, they move out. While moving they came across other air masses.

Air masses

The relative difference between temperature and moisture decide their interaction with one anotherThe border/ meeting region of the two air-mass => Front

Front

If cold air mass move faster than the other than it will lift the warmer one upward => cold front the slope will be steep = there will be sudden up-liftment of the warm air = cumulonimbus clouds =frontal rainfall

Cold front

If warmer air mass is more active than cold front => warm front slope will be gentler = there wont be sudden up-liftment of warm air = uniform prolonged rain drizzle

Warm front

Fronts

Also called as extra-tropical cyclone, travelling depressions, cold-core cyclone, wave cyclones

Frontal cyclone

Intense LP systemAir converges towards the centreClosed isobars In Northern hemisphere convergence anti-clockwise

Meaning of cycloneNormal isobar

Closed isobarIsobarThermally inducedBecause of high temperatureEx. LP at equatorConvectional rainfall at equatorUpliftment of warm airEx. LP at sub-polar LP beltFrontal rainfall

Dynamically inducedConditions for LPMovement of airmasses from their source regionThe warm and cold air mass face each otherA front is created between them Called Stationary front

Development of Frontal cyclone

Location of air massesCircular movementFormative stage of frontal cyclone

Cold air mass pushed the warm air massForced upliftment of warm air mass at the cold front =LP Two cold air mass convergence circular due to coriolis force

Development of Frontal cyclone

Interaction of air massesLP closed isobarsMature stage

One cold air mass climb over other cold air masswarm front is destroyedCalled occluded frontRapid change in temperature and pressureUnstable weather conditions

Occluded front

Frontolysis no great temperature difference between two cold air masses front dissipated LP reduced cyclone dissipated

Dissipation of frontal cyclone

Stationary frontFront

Occluded front

Frontolysis

Always west to east directionBecause influence of the wetserlies Gradual movement- Predictable weather

Path of the temperate cyclone

Distribution of temperate cyclonesHurricane N. AmericaTyphoon - ChinaLate summer Increased sea surface temperature = LPConvergence of air around LP zoneRising moist (wet) air => absolute instability

Tropical cyclone

Cloud formation =more and more moisture latent heat of evaporation => cumulo nimbus cloud => cycloneCoriolis force induce spiral movement of air

Tropical cycloneIntensification of LPConverging air near water surfaceCirculating air rises above (coriolis force)Diverging air at the top of cycloneMature Tropical cyclone

At the centre of the cyclone eye of the tropical cyclone. It is a pressure defect. Because, at eye a narrow stream of wind descend = is HP at eyeAt the eye, there is clear sky.Beyond eye wall extreme low pressureEye of the tropical cyclone

Move swiftlyIt is fuelled by moisture so when cyclone is cut-off from sea and move towards land it starts weakening

Properties of tropical cyclones

Distribution of tropical cycloneTemperate cyclone30-40 degree latitudeDynamically inducedDue to frontal interactionFormed over large areaMove west to eastGradual movement predictable8-20 degree latitudeThermally inducedDue to increasing SSTSmall areaMove east to westSwift movement- difficult to predict pathTropical cyclonecomparisonTemperate cycloneWind speed 40-50 kmphPressure gradient 980 mbPowerful on landAffect mainlandMore time to dissipateWind speed >120 kmphPressure gradient