TempTemperatueraturree
WhatWhat iiss temtemperaperature?ture?
Heat – form of energy that flows from one system or object to another b/c they have different temperatures
Temperature – a measure of the average kinetic energy of individual molecules . We feel the effect of temperature as sensible heat transfer from warmer to cooler objects
Temperature and Heat are relalated b/c changes inin temperature occur by absorption or emissioion (gainin/loloss) of heat energy
SSuurfarfaccee TTememperperaturaturee
During the day, SW iinputs usuallylly exceeds LW outputs and heatiing of the surface occurs
Latent and sensibiblele heat are also iimportant in determinining surface temperature (e.g. desert vs. oasis)
TTememperperatureature SSccalesales
KelvinKelvin (K)(K) == absabsoluteolute ttemperemperatuaturere scale,scale, -2-273.1573.15 degrdegreesees CelsiCelsiuuss oror 00 dedegreegree KK
CelsiusCelsius (C)(C) == interninternationalational sstandartandardd
FFaahrehrenheitnheit ((FF)) == uusedsed inin tthehe USUS
MeMeasurinasuringg TemTemperperatuaturere
TThhermermomeometerter –– anan instinstrumrumentent uusedsed toto meameasuresure temtemperatperatureure . Alcohol thermometer: alcohol has a freeziing point -112 C so itit is used for cold weather measurements . Mercury thermometer – mercury has a freezining poinint of -39 C so itit isis better suited for lless extreme environments
TThhermermomeometersters measumeasurere tetempmp bbasedased oonn ththee thethermalrmal prproperopertiesties ofof thethe liquidsliquids aabove:bove: - Fluids expand when heated, contract when cooleled - The rise and fallll ofof the fluidid isis measured usining calilibratiions marked on the tube
MeMeasurinasuringg TemTemperperatuaturere
Standard Temperature Measurement:
- Taken outdoors - Thermometer is placed wiithinin aa thermometer shelterlter - A white (for albedo) box with vents (for air flow) that shades the thermometer from direct sunlight - Temperatures taken at a standard height of 1.2m above the ground
DiffDiffereerentnt TemTemperperatuaturere MeaMeassururememenentsts::
Max temperature – higighest temp readining Min temperature – llowest temp readining Dailily mean temperature – average of the max and min dailyly temp
Monthlyly mean temperature – average of dailyly mean temps Annuall temperature range – dififference between the llowest and higighest monthlyly mean temperatures for a year
AirAir vsvs SurSurfaceface TTempemperateratureure
Air temperature iis measured a short disistance (usualllly 1.2m or 4ft) above the surface
Air temperature can be quite diifferent than surface temperature
However, airir temperature tends to mirror surface temperature
EartEarth’sh’s temptemperateratureure pattpatternserns iinnflfluuencedenced byby foufourr pphysichysicaall prproperoperties:ties:
1) LatLatiittudeude 2) ElEleevationvation 3) CloudCloud CCoveoverr 4) LanLandd vs.vs. ooceancean
WhatWhat factorfactorss contcontrolrol tetempermperatuature?re?
1)1) LatitLatitudeude
LaLatitittudeude
Latiitude controlsls: 1) Dayllength 2) Anglele of incidence
Insolation is the siinglele most important inflluence on temperature variatiions
Why don’t world temperature patterns follolow llatiitudinall bands?
LaLatitudetitude andand aiairr tetempermperaturaturee Seasonal range inin airir temperature iis strongly dependent on lalatiitude – inincreases as you get closeloser to the polesles . More direct rays of sunliglight during summer . Longer daylelength inin summer; shorter in wiinter
Equatorial lolocations may actualllly be warmer during an equinox than during a solstice!
Generallyly, airir temperature lalags behind solalar radiatioiation by one month over laland and by two months over water
2)2) AAltitudltitude/Ele/Eleevationvation
WhatWhat isis thethe imimpactpact ofof elevatelevatiioonn onon temtemperaperaturture?e?
ElEleevation:vation: temtemperaperatureture decrdecreaseseases withwith iinnccrreasingeasing elevationelevation withinwithin ththee trtropospopospherehere
At siimilar llatitudes, mountainous areas experience lower air temperatures than llocatioions near sea lelevel
Remember that densitity alslso decreases withith iincreasiing altltiitude: . As the atmos thinins, the no. of airir molemolecules decrease . Fewer moleculesles inin the air means less energy absorption . Less SW radiatioiation is reflected and scattered into space . Surface gains and looses energy more rapidly under lower atmospheric pressure
3)3) ClClooudud CoveCoverr
CloudCloud CCoover-ver- cloudsclouds areare tthehe mmostost vavariableriable ffactoractor influencinginfluencing thethe EEaarth’srth’s EBEB
Cover approximatelimately 50% of the earth and theirir efeffect on temperature depends on their type, heigight and density Moderate temperature → decreasinging daytiime temps and iincreasing nigighttime temps
Cllouds absorb and reflelect SW energy during the day → cooliling effect Cllouds absorb and reradiate LW energy at nigight → warming effect
4)4) LandLand vs.vs. OceOceanan
LanLandd andand WaterWater ContraContrastssts
- Land has dififferent thermall propertiies than water resultltiing inin dififferences inin temperature - Land and water absorb and store energy dififferentlyly b/c of the physicicall nature of laland and water
Four main differences: 5) Evaporation 6) Transparency 7) Speciificic Heat 8) Movement
LaLandnd-W-Waaterter CCoontrantrasststs
1)1) evapevaporatoratiioonn:: More energy at the ocean surface goes ininto evaporation than on land 84% of allll evaporation on earth occurs over the ocean Evaporatiion is a cooliling process Results in llower temperatures over oceans than on land
22)) trtranspaansparencyrency:: Lighight can be transmitted through water but not through lland Lighight strikiniking land does not penetrate but is absorbed → heat surface Energy transmits through water to a depth of approx. 60m Energy has a greater distribistribution wiithinin water than on land
LaLandnd-W-Waaterter CCoontrantrasststs
3)3) SpecificSpecific heaheatt:: Heat capacity of a substance When equal volumes of land and water are compared, water requiresires more energy to increase iits temperature than lland Water can holdld more heat than soilil (specific heat iis x4) Land heats and cools quick, water heats and coolsls slowslow
44)) mmovemeovementnt:: Land iis solidlid and does not move whereas water is flluid and capablele of movement Mixinging between warm and coldld llayers iis possible withiithin water and not possiblele wwithiithin land Mixinging spreads availalable energy over and even greater volume
WhatWhat iiss thethe iimmpactpact oonn dadaiilyly ttemperemperaturatures?es?
LESSLESS DIURNADIURNALL TTEMPEEMPERATRATUREURE CHANCHANGGEE!!
Marinine llocatioions have cooler days and warmer nigights than comparablele ininlaland llocatioions
Marinine effect (maritime)ime) – lolocatiions that exhibibitit the moderating iinfluences of the ocean. Smallller range between max and min dailyly and annuall temps.
Contininentall Effect (contininentallitity) – areas that are lless affected by the sea. Greater range between max and min dailily and annual temp.
DiDiuurnalrnal (Dail(Dailyy)) CycleCycle ofof AAirir TTememperperaattureure
Generallyly folllolows the sun; however, itit llags due to the delalay inin heatining the atmosphere
Coldldest airir temperature usuallyly occurs jusjust after sunrise – no solar radiiatiion during nigight
Warmest airir temperature occurs about 3pm when turbulenlent miixing beginins (warm bubbles of airir rise and are replalaced by colder airir from aloft)
EEndnd ofof mmataterialerial ccontaontaiinedned inin tthehe MiMidtdtermerm!!
DiDiuurnalrnal (Dail(Dailyy)) CycleCycle ofof AAirir TTememperperaattureure
An invinversion may occur inin the mornining hours since the earth’s surface cools rapidlidly when the sun sets
GlobGlobalal temtempeperatratureure papattertternsns
TTeempermperatuaturere papattertternsns rresultesult frfrom:om: - LatLatiittudeude - ElEleevationvation aabovebove seseaa levellevel - CloudCloud cocoverver - LanLand-ocead-oceann heheatingating ddiiffffereerencesnces
Maximuimum monthlyly mean temperature occurs inin Julyly (N. Hem) . Lag after summer solstiice b/c iinputs are stilll lalarger than outputs shortlly after max insolation . Similailar to lag in dailily air temperature
Minimuimum monthlyly mean temperature occurs inin January (N. Hem) . Lag after winterinter solsolstiice b/c iinputs are stililll smalsmallerler than outputs shortlly after min iinsolatiolation . Similailar to lag in dailily air temperature
HHoorizrizoontantall TempTempereraturaturee PattePattern:rn:
IsotIsotherhermsms –– lineslines ofof eequalqual tetempermperaturaturee . Trend east and west . Deviiate from trends due to mountainins and laland-ocean contrasts
TThhermermalal EEqquatouatorr –– isoisothermtherm connconnectingecting ppoointsints ofof highesthighest temtemperaperaturturee . Hovers around latititudininal equator . Shififts north inin summer (accordining to lolocatiion of max iinsolalatioion) . Shififts south iin wininter
JanuJanuaryary temptemperatueraturere pattepatterns:rns: . Temp decreases north and south of the thermal equator . Isotherms bend south over laland Cooler temps are found south over lland than over water Land lolooses heat more quickly than water . Lowest temp over Siberiaia (contiinental lolocation) . Isotherms move further south over mountaiinous regioions (elevation effect)
JulyJuly ttempeemperaturraturee ppatteratterns:ns: . Temperature stiillll decreases north and south of thermal equator . Lower temperature is S. Hem than at equivallent lalatiitudes inin N. Hem Max insolation iin N. Hem Shift iis not as dramatiic iin S. Hem b/c S. Hem has more oceans and leless lland area Milder wininter temps due to surrounding oceans (moderating effect) . Isotherms bend north over laland and mountainins
AnnuaAnnuall temptemperatueraturere rangerange:: Identiifieies areas of moderate or extreme annuall ttemp variations Most extreme variatioion over Siberia . Continental locatiion . Extreme north latituditude Moderate alolong the equator . Litittle variatiion inin iinsolatiolation during the year . Litittle temperature variatiions annuallyly Moderate over the S. Hem . Moderatiing effect of large oceans and lilittlele lland . Most extremes occur over desert areas (low cloud cover)
PPrrobloblemem SetSet #3#3
WWindind ChilChilll andand HeaHeatt IndIndexex
AirAir tetemmperaperatuturere aandnd thethe HHuumamann BodBodyy::
The human body responds not onlyly to the air temperature but also to winind speed and humidity (amount of water vapour inin the air).
- Body trieies to mainintainin temperature of 36.8 C - Winind and humiidity can exacerbate the effect of airir temperature on the human body
→Wind Chililll Factor
WWiindnd CChhillill FacFacttor:or:
ColdCold weatweatherher isis gregreatestatest cacauseuse ofof weathweatherer rrelatedelated deatdeathh inin USUS.. . Windind enhances the rate at whicich the body lloses heat to the atmosphere . Makes itit feell coldlder than the air temperature actuallyly isis . The “wiind chillll inindex” was developed to describe the relative disiscomfort/danger resultltiing from the combinination of windind and temp
WWinindd ChilChilll InIndex:dex:
Since 2000, WCI calculalated usining the winind speed at average heigight (5 feet) of the human body’’s face Incorporate modern heat transfer theory Use a consistent standard for skinin tisissue resisistance Assumes the worst case scenario for solalar radiaiatioion (clelear night sky) Adjjustments for solalar radiatiion (i.i.e. the impaimpact of sun) for a variety of sky condititiions (sunny, partly sunny and cloloudy)
TToo calculatecalculate wiwindnd chillchill::
WC (F) = 35.74 + 0.6215 * T – 35.75 * (V0.16) + 0.4275 * T * (V0.16)
Examplele: Newark → Wednesday January 17th 2007 Hiigh Temperature 35 F Wind speed = 13 mph WC (F) = 35.74 + 0.6215 * 35 – 35.75 * (130.16) + 0.4275 *35* (130.16)
WC = 18.55 F
WindWind chillchill warnwarninging →→ wwindind chillchill temptemperatueraturere iiss fforeoreccaastst toto bebe minuminuss 2525 ddegreegreeses FF oorr lowerlower
WindWind chillchill advisoadvisoryry →→ windwind chillchill ttempeemperaturaturere isis foforecarecasstt toto bebe betbetwweeeenn mmiinunuss 1010 toto mmiinnusus 2424 degrdegreesees FF
Winind chililll does not affect your car’s antifreifreeze protectioion or freeziing pipipes. It’s’s an iindicator of how to dress properly for wiinter weather: . Entrapped insulatiing airir wwarmed by body heat . Loose-fiitting, llighightweight, warm clothinging iin several lalayers . Tiightlly-woven, water-repellant, hooded outer garments withith mittmittens
Onlyly cold wininter temperatures take a greater weather-related death tollll than the summer’s heat and humidity.
HeatHeat IndexIndex:: . Is an accurate measure of how hot isis reallyly feelsls when the affect of humidityity are added to higigh temperature . Human body contains severall mechanisms to mainintain itits iinternal operatining temperature 98.6 F . When threatened witith above “normal” temperatures, the body wililll try to disissipipate excess heat: Varyining circulirculation of blood Losing water through the skin and sweat glands panting
HeatHeat IndexIndex:: . Hiigher humiditity reduces the body’s abiilitylity to evaporate perspirairatiion . Thisis llessens the body’’s abililitity to regulalate temperature by cooliling Condititiions can exceed the body’s’s abiabilility to cope; sunstroke, heat cramps, heat exhaustion
TThhee HIHI chachartrt sshhowsows actuaactuall airair tetempermperatuaturere anandd rrelativeelative humhumidityidity . Thisis chart isis based on shady, lilight wiind condititiions . Exposure to dirirect sunligight can inincrease the HI by up to 15 F
Examplele: At 90% relativelative humiidity and 90 F HI = 120 F (cat 2 risk)
To actually calculalate the HI:
HI =16.923+((1.85212*10^-1)*T)+(5.37941*RH)-((1.00254*10^-1)*T*RH) +((9.41695*10^-3)*T^2)+((7.28898*10^-3)*RH^2)+((3.45372*10^- 4)*T^2*RH)-((8.14971*10^-4)*T*RH^2)+((1.02102*10^-5)*T^2*RH^2)- ((3.8646*10^-5)*T^3)+((2.91583*10^-5)*RH^3)+((1.42721*10^- 6)*T^3*RH)+((1.97483*10^-7)*T*RH^3)-((2.18429*10^-8)*T^3*RH^2) +((8.43296*10^-10)*T^2*RH^3)-((4.81975*10^-11)*T^3*RH^3)