MET$1$–$THE$ATMOSPHERE$
!
CONVERSION$FACTORS$ LAPSE$RATES$ TROPOPAUSE$
$ $ $
• 1!nm!=!6080!ft!=!1.852!km$ • Normal! +ve! lapse! rate.! (Decreases! approx! • Separates!troposphere!from!stratosphere$
• 1!m!=!3.28!ft!(x3,!+!10%)$ 20C!/!1000ft)$ • Marks! the! point! where! temperature! stops!
• Surface!inversion,!Zve!lapse!rate.$ falling!(average!Z56.5!/!11km!(36,000ft).$
• Inversion!aloft,!+ve!lapse!rate$ • Height!varies!with!temperature.$
COMPOSITION$ • Isothermal!(no!change!with!altitude)$ • At!poles:!25,000!ft!/!7.5!km!/!Surface!Z100C!/!
$ Tropo!Temp!Z450C$
• Atmosphere!has!no!specific!upper!limit.$ • Equator:!55,000ft!/!17!km!/!Surface!+400C!/!
• Nitrogen!(N2)!! ! 78%$ Tropo!Temp!Z750C$
• Oxygen!(O2)!! ! 21%$ • The! ‘steps’! in! the! tropopause! give! rise! to!
• Argon!(A)!! ! ! 0.93%$ strong!upper!winds!(jet!sreams)$
• Carbon!Dioxide!(CO2)! 0.03%$ • Higher!in!summer!compared!to!winter.$
$
• Hydrogen!(H)! Trace$ STRATOSPHERE$
• Ozone!(O3)!! Filters!and!absorbs!UV$ $
• Water!Vap!(H2O)! Gas!state!of!water$ • Isothermal! then! an! increase! with! height! due! to!
• Solid!particles! Pollution*$ Ozone!layer!heating.$
$ • Only! contains! about! 1%! of! atmospheres! water!
vapour! so! is! absolutely! stable! with! very! little!
• Concentration! %! of! gases! remains! constant!!
weather.$
with! the! exception! of! water! vapour! which!
• Stratosphere! extends! from! 11! km! –! 50! km! at!
decreases!with!altitude.$ mid!latitudes.$
TRPOPOSPHERE$ • Reaches!00C!at!stratopause.$
VARIATIONS$WITH$HEIGHT$ $
$ • Almost! all! water! vapour! within! the!
• Pressure!decreases!with!height.$ atmosphere! is! contained! here! and! hence!
• Density!decreases!with!height.$ this!is!where!most!of!the!weather!occurs.$
• Temperature!varies!with!height.$ • +ve!lapse!rate$
ATMOSPHERIC$PROPERTIES$
$
• Air!is!a!poor!conductor!of!heat.$
• The!! gases! within! the! atmosphere! obey! the!
gas!laws.$
, MET$3$–$HEAT$&$TEMPERATURE$
!
TEMPERATURE$SCALES$ SOLAR$RADIATION$ HEAT$TRANSFER$
$ $ $
• Celsius!:!Freeze!0! C!/!Boil!100!0!C$
0! • Short$wave!radiation$ • Conduction$
• Farenheight:!Freeze!32!0!F!/!Boil!212!0!F$ • Only!occurs!during!daytime$ • Convection$(due!density!changes)$
• Kelvin:!Freeze!273!K!/!Boil!373!K$ • Only! about! 45%! of! the! radiation! actually! • Advection$(horizontal!movement!of!air)$
$ reaches!the!surface!of!the!earth:$ • Latent$heat$(absorbed!if!melt!/!evaporate)$
!
• C!!!F:!!!!!! !! + 32! o Absorbed!by!atmosphere!and!clouds$ !
o Scattered!by!atmosphere$ • Irregular! mixing! of! convection! and!
• C!!!K:!+273!(Approx!double,!add!30)$
o Scattered!and!reflected!by!clouds$ advection!gives!rise!to!turbulence.$
$ o Reflected! by! earth! (albedo! effect! –!
• Celsius!is!used!for!meteorological!purposes$ greatest!snow!/!smallest!rainforest)$
• Heats! the!surface$ of$ the$ earth$ which!then! DIURNAL$VARIATION$
REPORTING$TEMPERATURE$ heats!the!air!through!conduction!etc.$ $
$
• Daily!changes!of!temperature!=!DV$
• Temperature!is!rounded$when!reported.$
INSOLATION$ • Max!temp!=!Noon$+$2$Hrs$
• 2.2!becomes!2$
$ • Min!temp!=!Sunrise$+$30$mins$
• 2.5!becomes!3$
• The!amount!of!solar!radiation! incident!on!a! • Factors!affecting!DV:$
• Z2.5!becomes!M2$
unit$area$of!the!earth’s!surface.$ o Wind!–!Strong!wind!reduces!max!+!min$
• Z0.5!becomes!M0$
• Affected!by:$ o Cloud!–!Clouds!reduces!max!+!min$
o Angle!of!incidence!(wider!at!poles)$ o Surface! –! Oceans! have! very! small! DV,!
MEASURING$TEMPERATURE$ o Nature!of!surface!(sand!vs!water)$ deserts!have!the!max!DV.$
$ o Transparency!of!atmos.!(cloud,!dust)$ • Max!DV!occurs!(inversion!also!likely)!with:$
• Measured!with!a!Stevenson$Screen.$ o Calm!winds$
• Measured! at! a! height! of! 4ft$ AGL$ (avoids! o Clear!conditions$
ground!heating).$ RADIATION$FROM$EARTH$ o Over!land!(especially!dry!ground)!
$
• Long$wave$radiation$
NOCTURNAL$/$TERRESTRIAL$ • Occurs!24$Hrs$
RADIATION$INVERSION$ • Negligible!during!day!due!to!solar!radiation.$
$ • Net$outflow$of!heat!at!night!=!surface$cools$
• Occurs! with! weak$ winds$ and! • Too! high! concentrations! of! carbon! dioxide! and!
clear$skies$at!night.! water! vapour! (greenhouse$ gases)! act! like! a!
• Creates!a!large!outbound!radiation! blanket!and!can!leading!to!warming.$
and!surface!is!cooled.! • A! calm! and! clear! night! will! be! cooler! than! a!
! cloudy!night!as!radiation!from!Earth’s!surface!is!
• Warmer! air! above! leads! to! an! allowed!to!slip!into!space.$
inversion.!
, ! MET$2$–$INTERNATIONAL$STANDARD$ATMOSPHERE$
LATENT$HEAT$ ISA$TEMPERATURE$ ISA$PRESSURE$
$ ! !
Water!Vapour$ • MSL!Temp!=!+15!0C! • MSL!Pressure!=!1013.25!hPa!/!29.92!in!Hg!
Liquid$ • +!ve!Lapse!Rate!(MSL!–!11km)! • Lapse!Rate!(MSL!–!5.5!km)!
$ Solid! o 1.980C!/!1000!ft!||!6.50C!/!1!km! o 27!ft/!hPa!||!8!m!/!hPa!
! • Lapse!Rate!(11!–!20!km):!Z56.5!0C! • Lapse!Rate!(5.5!km!+):!
• Going!up!the!steps!requires!energy!so!latent! • +!ve!Lapse!Rate!(20!–!32km)! o 50!ft/!hPa!||!15!m!/!hPa!
heat!is!absorbed.! o 0.30C!/!1000!ft!||!10C!/!1!km! • Half!Pressure!=!5.5!km!/!18,000!ft!
• Substance! stays! the! same! temperature! but! o A.K.A!Inversion! o =>!Half!the!mass!of!the!atmosphere!can!
the! temperature! of! the! surroundings! is! ! be!found!in!the!lowest!5.5!km!(EASA!use!
changed.! 5km!sometimes)!
• Convection! and! condensation! contribute!
most!to!atmospheric!waraming.!
• Polar!00!isotherm:!0!ft!
• Temperate!00!isotherm:!6,000!–!10,000!ft!
• Tropical!00C!isotherm:!16,000!–!18,000!ft! ISA$PRESSURE$VALUES$
!
JSA$ • 30,000!ft! ! 300!hPa!
! ! • 18,000!ft! ! 500!hPa!
• Jet!Standard!Atmosphere! • 10,000!ft! ! 700!hPa!
WHY$ISA?$ • 5,000!ft! ! 850!hPa!
• Constant!20C!/!1000!ft!for!planning!
! • 0!ft! ! ! 1013.25!hPa!
• International!Standard!
• Relate!performance!of!a/c!to!know!values! ISA$DENSITY$
• Calibration!of!pressure!instruments! ! ISA$DEVIATION$
• Manufacture!and!testing!of!a/c! • MSL!Density!=!1.225!kg!/!m3! !
!
• Half!Density!=!20,000!ft! • ISA!Deviation!=!Ambient!(OAT)!Z!ISA!
, ! MET$4$–$ATMOSPHERIC$PRESSURE$
VARIATION$OF$PRESSURE$WITH$HEIGHT$ APLR$ DIURNAL$VARIATION$
! ! !
• The!rate$of$pressure$decrease$will!reduce$ • Ambient$Pressure$Lapse$Rate$ • Amplitude!greatest!at!equator!(~!3!hPa)$
as!height!increases.! !"#
• !"#$ = ! $ • Mid!Latitudes:!~!0.5!–!1!hPa$
• As! altitude! increases,! the! weight! of! the! • Poles:!Negligible$
• K!=!Mean!temperature!in!Kelvin$
atmosphere!above!you!will!decrease.!
• P!=!Mean!pressure$
$
• Pressure&at&MSL&is&1000&hPa&and&temperature&
PRESSURE$VARIATION$WITH$ is&+20& 0C.&An&aircraft&is&flying&at&the&910&hPa&
TEMPERATURE$ level&where&temperature&is&A6& 0C.&What&height&
! is&it&flying&at?!
• Cold$ air! is! more! dense! so! more! rapid! • Mean!pressure!=!(1000Z910)/2!=!955!hPa$
decrease!in!pressure!with!height.! • Mean! temperature! =! [(20)+(Z6)]/2! =! +7! =!
• Warm$ air$ is! less! dense! so! slower! decrease! 280!K$ PRESSURE$MEASUREMENTS$
in!pressure!with!height!(compared!to!ISA).! • APLR!=![(96x280)/955]!=!28.15!ft!/!hPa$ !
• When! flying! from! ISA! to! colder! air,! aircraft! • Pressure!difference!is!(1000!–!910)!=!90!hPa$ • QFE:$ Pressure! observed! at! a! specific!
will!descend!but!still!show!18,000ft.!High$to$ • 90!x!28.15!=!2533.5!ft!AMSL$ location!with!a!datum!of!0!ft.$
low,$watch$out$below!! $ • QFF:$ QFE! changed! to! MSL! pressure! using!
• The! pressure! in! a! column! of! warm! air! is! • An!APLR!<$27’$/$hPa$=$Cold$Air$ APLR.$Used!on!synoptic!chart.$
likely!to!be!greater!than!the!pressure!at!the! • An!APLR!>$27’$/$hPa$=$Warm$Air$ !"#$"%&'!!"#$!!
o +/!−!!"# = !""!
same!height!in!a!cold!column!of!air.! $
!"#$
o !dd!if!airfield!is!above!MSL!
• Shortest! distance! between! two! pressure! • QNH:$ QFE! changed! to! MSL! pressure! using!
levels! occurs! when! pressure! increases! and! ISA$lapse!rates.$
temperature!decreases.$ !"#$"%&'!!"#$!!
o !"
+/!−!!"# = !"#!
!! o !dd!if!airfield!is!above!MSL!
!
!
CONVERSION$FACTORS$ LAPSE$RATES$ TROPOPAUSE$
$ $ $
• 1!nm!=!6080!ft!=!1.852!km$ • Normal! +ve! lapse! rate.! (Decreases! approx! • Separates!troposphere!from!stratosphere$
• 1!m!=!3.28!ft!(x3,!+!10%)$ 20C!/!1000ft)$ • Marks! the! point! where! temperature! stops!
• Surface!inversion,!Zve!lapse!rate.$ falling!(average!Z56.5!/!11km!(36,000ft).$
• Inversion!aloft,!+ve!lapse!rate$ • Height!varies!with!temperature.$
COMPOSITION$ • Isothermal!(no!change!with!altitude)$ • At!poles:!25,000!ft!/!7.5!km!/!Surface!Z100C!/!
$ Tropo!Temp!Z450C$
• Atmosphere!has!no!specific!upper!limit.$ • Equator:!55,000ft!/!17!km!/!Surface!+400C!/!
• Nitrogen!(N2)!! ! 78%$ Tropo!Temp!Z750C$
• Oxygen!(O2)!! ! 21%$ • The! ‘steps’! in! the! tropopause! give! rise! to!
• Argon!(A)!! ! ! 0.93%$ strong!upper!winds!(jet!sreams)$
• Carbon!Dioxide!(CO2)! 0.03%$ • Higher!in!summer!compared!to!winter.$
$
• Hydrogen!(H)! Trace$ STRATOSPHERE$
• Ozone!(O3)!! Filters!and!absorbs!UV$ $
• Water!Vap!(H2O)! Gas!state!of!water$ • Isothermal! then! an! increase! with! height! due! to!
• Solid!particles! Pollution*$ Ozone!layer!heating.$
$ • Only! contains! about! 1%! of! atmospheres! water!
vapour! so! is! absolutely! stable! with! very! little!
• Concentration! %! of! gases! remains! constant!!
weather.$
with! the! exception! of! water! vapour! which!
• Stratosphere! extends! from! 11! km! –! 50! km! at!
decreases!with!altitude.$ mid!latitudes.$
TRPOPOSPHERE$ • Reaches!00C!at!stratopause.$
VARIATIONS$WITH$HEIGHT$ $
$ • Almost! all! water! vapour! within! the!
• Pressure!decreases!with!height.$ atmosphere! is! contained! here! and! hence!
• Density!decreases!with!height.$ this!is!where!most!of!the!weather!occurs.$
• Temperature!varies!with!height.$ • +ve!lapse!rate$
ATMOSPHERIC$PROPERTIES$
$
• Air!is!a!poor!conductor!of!heat.$
• The!! gases! within! the! atmosphere! obey! the!
gas!laws.$
, MET$3$–$HEAT$&$TEMPERATURE$
!
TEMPERATURE$SCALES$ SOLAR$RADIATION$ HEAT$TRANSFER$
$ $ $
• Celsius!:!Freeze!0! C!/!Boil!100!0!C$
0! • Short$wave!radiation$ • Conduction$
• Farenheight:!Freeze!32!0!F!/!Boil!212!0!F$ • Only!occurs!during!daytime$ • Convection$(due!density!changes)$
• Kelvin:!Freeze!273!K!/!Boil!373!K$ • Only! about! 45%! of! the! radiation! actually! • Advection$(horizontal!movement!of!air)$
$ reaches!the!surface!of!the!earth:$ • Latent$heat$(absorbed!if!melt!/!evaporate)$
!
• C!!!F:!!!!!! !! + 32! o Absorbed!by!atmosphere!and!clouds$ !
o Scattered!by!atmosphere$ • Irregular! mixing! of! convection! and!
• C!!!K:!+273!(Approx!double,!add!30)$
o Scattered!and!reflected!by!clouds$ advection!gives!rise!to!turbulence.$
$ o Reflected! by! earth! (albedo! effect! –!
• Celsius!is!used!for!meteorological!purposes$ greatest!snow!/!smallest!rainforest)$
• Heats! the!surface$ of$ the$ earth$ which!then! DIURNAL$VARIATION$
REPORTING$TEMPERATURE$ heats!the!air!through!conduction!etc.$ $
$
• Daily!changes!of!temperature!=!DV$
• Temperature!is!rounded$when!reported.$
INSOLATION$ • Max!temp!=!Noon$+$2$Hrs$
• 2.2!becomes!2$
$ • Min!temp!=!Sunrise$+$30$mins$
• 2.5!becomes!3$
• The!amount!of!solar!radiation! incident!on!a! • Factors!affecting!DV:$
• Z2.5!becomes!M2$
unit$area$of!the!earth’s!surface.$ o Wind!–!Strong!wind!reduces!max!+!min$
• Z0.5!becomes!M0$
• Affected!by:$ o Cloud!–!Clouds!reduces!max!+!min$
o Angle!of!incidence!(wider!at!poles)$ o Surface! –! Oceans! have! very! small! DV,!
MEASURING$TEMPERATURE$ o Nature!of!surface!(sand!vs!water)$ deserts!have!the!max!DV.$
$ o Transparency!of!atmos.!(cloud,!dust)$ • Max!DV!occurs!(inversion!also!likely)!with:$
• Measured!with!a!Stevenson$Screen.$ o Calm!winds$
• Measured! at! a! height! of! 4ft$ AGL$ (avoids! o Clear!conditions$
ground!heating).$ RADIATION$FROM$EARTH$ o Over!land!(especially!dry!ground)!
$
• Long$wave$radiation$
NOCTURNAL$/$TERRESTRIAL$ • Occurs!24$Hrs$
RADIATION$INVERSION$ • Negligible!during!day!due!to!solar!radiation.$
$ • Net$outflow$of!heat!at!night!=!surface$cools$
• Occurs! with! weak$ winds$ and! • Too! high! concentrations! of! carbon! dioxide! and!
clear$skies$at!night.! water! vapour! (greenhouse$ gases)! act! like! a!
• Creates!a!large!outbound!radiation! blanket!and!can!leading!to!warming.$
and!surface!is!cooled.! • A! calm! and! clear! night! will! be! cooler! than! a!
! cloudy!night!as!radiation!from!Earth’s!surface!is!
• Warmer! air! above! leads! to! an! allowed!to!slip!into!space.$
inversion.!
, ! MET$2$–$INTERNATIONAL$STANDARD$ATMOSPHERE$
LATENT$HEAT$ ISA$TEMPERATURE$ ISA$PRESSURE$
$ ! !
Water!Vapour$ • MSL!Temp!=!+15!0C! • MSL!Pressure!=!1013.25!hPa!/!29.92!in!Hg!
Liquid$ • +!ve!Lapse!Rate!(MSL!–!11km)! • Lapse!Rate!(MSL!–!5.5!km)!
$ Solid! o 1.980C!/!1000!ft!||!6.50C!/!1!km! o 27!ft/!hPa!||!8!m!/!hPa!
! • Lapse!Rate!(11!–!20!km):!Z56.5!0C! • Lapse!Rate!(5.5!km!+):!
• Going!up!the!steps!requires!energy!so!latent! • +!ve!Lapse!Rate!(20!–!32km)! o 50!ft/!hPa!||!15!m!/!hPa!
heat!is!absorbed.! o 0.30C!/!1000!ft!||!10C!/!1!km! • Half!Pressure!=!5.5!km!/!18,000!ft!
• Substance! stays! the! same! temperature! but! o A.K.A!Inversion! o =>!Half!the!mass!of!the!atmosphere!can!
the! temperature! of! the! surroundings! is! ! be!found!in!the!lowest!5.5!km!(EASA!use!
changed.! 5km!sometimes)!
• Convection! and! condensation! contribute!
most!to!atmospheric!waraming.!
• Polar!00!isotherm:!0!ft!
• Temperate!00!isotherm:!6,000!–!10,000!ft!
• Tropical!00C!isotherm:!16,000!–!18,000!ft! ISA$PRESSURE$VALUES$
!
JSA$ • 30,000!ft! ! 300!hPa!
! ! • 18,000!ft! ! 500!hPa!
• Jet!Standard!Atmosphere! • 10,000!ft! ! 700!hPa!
WHY$ISA?$ • 5,000!ft! ! 850!hPa!
• Constant!20C!/!1000!ft!for!planning!
! • 0!ft! ! ! 1013.25!hPa!
• International!Standard!
• Relate!performance!of!a/c!to!know!values! ISA$DENSITY$
• Calibration!of!pressure!instruments! ! ISA$DEVIATION$
• Manufacture!and!testing!of!a/c! • MSL!Density!=!1.225!kg!/!m3! !
!
• Half!Density!=!20,000!ft! • ISA!Deviation!=!Ambient!(OAT)!Z!ISA!
, ! MET$4$–$ATMOSPHERIC$PRESSURE$
VARIATION$OF$PRESSURE$WITH$HEIGHT$ APLR$ DIURNAL$VARIATION$
! ! !
• The!rate$of$pressure$decrease$will!reduce$ • Ambient$Pressure$Lapse$Rate$ • Amplitude!greatest!at!equator!(~!3!hPa)$
as!height!increases.! !"#
• !"#$ = ! $ • Mid!Latitudes:!~!0.5!–!1!hPa$
• As! altitude! increases,! the! weight! of! the! • Poles:!Negligible$
• K!=!Mean!temperature!in!Kelvin$
atmosphere!above!you!will!decrease.!
• P!=!Mean!pressure$
$
• Pressure&at&MSL&is&1000&hPa&and&temperature&
PRESSURE$VARIATION$WITH$ is&+20& 0C.&An&aircraft&is&flying&at&the&910&hPa&
TEMPERATURE$ level&where&temperature&is&A6& 0C.&What&height&
! is&it&flying&at?!
• Cold$ air! is! more! dense! so! more! rapid! • Mean!pressure!=!(1000Z910)/2!=!955!hPa$
decrease!in!pressure!with!height.! • Mean! temperature! =! [(20)+(Z6)]/2! =! +7! =!
• Warm$ air$ is! less! dense! so! slower! decrease! 280!K$ PRESSURE$MEASUREMENTS$
in!pressure!with!height!(compared!to!ISA).! • APLR!=![(96x280)/955]!=!28.15!ft!/!hPa$ !
• When! flying! from! ISA! to! colder! air,! aircraft! • Pressure!difference!is!(1000!–!910)!=!90!hPa$ • QFE:$ Pressure! observed! at! a! specific!
will!descend!but!still!show!18,000ft.!High$to$ • 90!x!28.15!=!2533.5!ft!AMSL$ location!with!a!datum!of!0!ft.$
low,$watch$out$below!! $ • QFF:$ QFE! changed! to! MSL! pressure! using!
• The! pressure! in! a! column! of! warm! air! is! • An!APLR!<$27’$/$hPa$=$Cold$Air$ APLR.$Used!on!synoptic!chart.$
likely!to!be!greater!than!the!pressure!at!the! • An!APLR!>$27’$/$hPa$=$Warm$Air$ !"#$"%&'!!"#$!!
o +/!−!!"# = !""!
same!height!in!a!cold!column!of!air.! $
!"#$
o !dd!if!airfield!is!above!MSL!
• Shortest! distance! between! two! pressure! • QNH:$ QFE! changed! to! MSL! pressure! using!
levels! occurs! when! pressure! increases! and! ISA$lapse!rates.$
temperature!decreases.$ !"#$"%&'!!"#$!!
o !"
+/!−!!"# = !"#!
!! o !dd!if!airfield!is!above!MSL!
!
