PBLandCloudMacrophysicsinCAM

SungsuPark

CGD.NCAR

CAMTutorial

Jul.28.2009

OUTLINE

I.  ParameterizaKonofSymmetricTurbulence(i.e.,PBLScheme)•  DryTurbulenceScheme(CAM3PBL)

•  MoistTurbulenceScheme(CAM4PBL)

II.  CloudMacrophysics•  NetCondensaKonRateofWaterVaporintoCloudLiquid(Q)•  CloudFracKon(a)

•  VerKcalOverlapofCloudFracKon

DEFINITIONS

 ModelNames

•  CAM3.5:CAM3.0+Revised Deep Convection +etc.

•  CAM4 :CAM3.5+All New Atmospheric Physics (~CAMUW )

I.ParameterizaKonofSymmetricTurbulenceinCAM

€

∂A ∂t

= − V ⋅ ∇A + Q A −

∂∂z

′ w ′ A

AdiabaKcMixingbyTurbulences

SymmetricTurbulence

(PBLScheme~SymmetricTurbulenceScheme)

AsymmetricTurbulence

(ConvecKonScheme~AsymmetricTurbulenceScheme)

€

′ w ′ A = (wu − w ) ⋅ (Au − A )

€

Au − A = −ΓA ⋅ l

€

′ w ′ A = −l ⋅ l ⋅ ∂u ∂z

⋅ S ⋅ ΓA

SingleSmall‐ScaleTurbulence

€

ΓA ≡ ∂A ∂z

€

l

€

z €

A

€

wu − w ≈ uu − u ⋅ S = l ⋅ ∂u ∂z

⋅ S

€

KA

€

′ w ′ A = −KA ⋅ ΓA − γA( )

Non‐LocalTerm

€

′ w ′ A = −l ⋅ l ⋅∂ u∂z

⋅ S ⋅ ΓA

€

′ w ′ A = l ⋅V ( ′ w ′ θ v )o,( ′ w ′ u )o; e( ) ⋅ S ⋅ ΓA , e ≡ 0.5 ⋅ ( ′ u 2 + ′ v 2 + ′ w 2)

€

∂∂t

′ w ′ A = −∂∂z

′ w ′ w ′ A + ... , ′ w ′ w ′ A = −l ⋅V ( e) ⋅ S ⋅ ∂∂z

′ w ′ A

€

A(t + Δt,z =1)A(t + Δt,z = 2)A(t + Δt,z = 3)A(t + Δt,z = 4)

=

c11 c12 c13 c14c21 c22 c23 c24c31 c32 c33 c34c41 c42 c43 c44

⋅

A(t,z =1)A(t,z = 2)A(t,z = 3)A(t,z = 4)

€

∂∂t

′ w ′ w ′ A = −∂∂z

′ w ′ w ′ w ′ A + ... , ′ w ′ w ′ w ′ A = −l ⋅V ( e) ⋅ S ⋅ ∂∂z

′ w ′ w ′ A

CAM3DryTurbulenceSchemewithNon‐LocalTerm

CAM4MoistTurbulenceScheme

HigherOrderClosure

TransilientTheory

€

′ w ′ A = −KA ⋅∂A ∂z

− γA

€

KA = l ⋅V ⋅ SA

€

γA

€

l

€

′ w ′ θ v( )o≤ 0

€

u*

€

k ⋅ z ⋅ 1− z h( )2

€

lc

€

u*3 + 0.6 ⋅ w*

3( )1/ 3

€

lc ⋅∂ u

∂z

€

Sm

€

V

€

Sh

€

1+10 ⋅ Ri ⋅ 1+ 8 ⋅ Ri( )( )−1 , Ri > 0€

1−18 ⋅ Ri( )1 2 , Ri ≤ 0

€

φm,u−1

€

φh,u−1€

1

€

Prz= 0.1h−1

€

u*

€

φm,s−1

€

φh,s−1

€

γ h

€

γ h

€

0

€

z = 0.1⋅ h

€

z = h

€

V

€

Sm

€

Sh

€

u*,u*θ*,u*q*[ ]

€

θv

€

′ w ′ θ v( )o> 0

1stOrderNon‐LocalClosureforDryTurbulence:CAM3

€

u*,u*θ*,u*q*[ ]

€

l€

e

€

k ⋅ z( )−1 + η ⋅ lc( )−1[ ]−1

€

Sm

€

V

€

Sh

€

z = h

€

Δz

€

Sm

€

Sh

€

We €

Sm

€

Sh

€

1

€

1€

k ⋅ z( )−1 + η ⋅ lc( )−1[ ]−1

€

e€

θv

1.5OrderLocalClosureforMoistTurbulence:CAM4

DryStablePBL:GABLS

DryConvecKvePBL

DryConvecKvePBL

€

u* = ′ w ′ u ( )o

2

€

w* = (g /θv ) ⋅ ′ w ′ θ v( )o⋅ h[ ]

1/ 3

€

w* = 2.5 ⋅ (g /θv ) ⋅ ′ w ′ θ v( )(z)0

h

∫ ⋅ dz

1/ 3

€

e = 6 ⋅ le⋅ (g /θv ) ⋅ ′ w ′ θ v − ′ w ′ u ⋅ ∂u

∂z

+ 24 ⋅

lh⋅ e − e( )

ComparisonofTurbulenceVelocity

CAM3DryTurbulence

CAM4MoistTurbulence

CAM4handleselevatedsourcesofturbulentenergy.CriKcalforsimulaKngmoistturbulenceassociatedwithclouds.

[Nicholls1984,Quart.J.R.Met.Soc.]

LWRadiaKveFluxatthetopofCloud

Cloud

PBL

[Wm‐2]

LW LWZ[m]

270 350

StrongLWcoolingisconfined

atthestratocumulustop.

TURBULENCEGENERATEDBYBOUNDARYHEATING

Warmairrises&

Coldairsinks

PotenKalenergyisconvertedtokineKcenergy

Turbulenceisgenerated

SurfaceWarmingor

TopCoolingMBLTop

MBLBase

TurbulenceisgeneratedbyMBLtopLWcoolingdrivenbystratocumulus

TURBULENCEGENERATEDBYCONDENSATIONHEATING

UnsaturatedPerturbaKon

TheperturbedairparcelwillreturntoitsoriginalposiKon

Turbulenceisdissipated

SaturatedPerturbaKon

TheperturbedairparcelwillconKnueitsoriginalmoKon

Turbulenceisgenerated

TurbulenceisgeneratedbycondensaKon‐evaporaKonheaKng,whichisinturncontrolledbycloudfracKonwithinthegrid.

Cloud‐topLWcooling

Cloud‐RadiaKon‐TurbulenceInteracKons

• SustainSaturatedPBLTop• Deeper,Drier,Well‐MixedmeanPBL

Entrainment

CondensaKon‐EvaporaKon

Cloud‐ToppedPBL:DYCOMS

FogAmount.JJA.

ObservaKon

CAM35

CAM4

SUMMARY

IncontrasttothedryturbulenceschemeinCAM3,themoistturbulenceschemeinCAM4takesintoaccountof

elevatedsourcesofTKEassociatedwithclouds.

CAM4successfullysimulatescloud‐toppedPBLaswellasdryPBL.

II.CloudMacrophysicsinCAM

WHATISCLOUD?

CLOUD:Thesumofvolumeelementscontainingcondensates.5keyproperKes:a,LWC,IWC,N(rl),N(ri)

Liquid

liquiddroplet

icecrystal

volumeelement

vaporflux

vaporpressure

CLI :Heterogeneous(Immersion)freezing Bergeron‐FindeisendeposiKonfreezingCLS :AccreKonofcloudliquidbysnow Bergeron‐FindeisenconversionCLR:Autoconversionofcloudliquidintorain AccreKonofcloudliquidbyrainCIS :Autoconversionofcloudiceintosnow AccreKonofcloudicebysnowCRS :AccreKonofrainbysnow Heterogeneousfreezing Homogeneousfreezing

CSED,L :SedimentaKonofcloudliquidCSED,I :SedimentaKonofcloudiceEL :EvaporaKonofsedimentedcloudliquidEI :EvaporaKonofsedimentedcloudiceER :EvaporaKonofrainES :EvaporaKonofsnowQL :NetcondensaKonintocloudliquidQI :NetcondensaKonintocloudice

CLOUDLIQUID

CLOUDICE

RAIN SNOW

CLI

CRS

CLS CIR=0CLR CIS

QL QI

ER ES

CSED,LEL CSED,I EI

Self‐CollecKon Self‐CollecKon

CondensateSystem(a)

ATc,Aqt

WhatdoesCloudMacrophysicsdo?

• CondensaKonrateofwatervaporintocloudliquid(Q)

• CloudfracKon(a)

• VerKcaloverlapofcloudfracKon

I.BULKSATURATIONADJUSTMENT

€

a(U)

€

ˆ U =1

in‐cloudcondensaKon

clearskyevaporaKon

changeofcloudfracKon

Aqv>0

€

ˆ Q cloud > 0 , ˜ Q clear ≥ 0 , ∂a∂t

> 0

Aql>0

€

ˆ Q cloud = 0 , ˜ Q clear < 0 , ∂a∂t

= 0

AT>0

€

ˆ Q cloud < 0 , ˜ Q clear = 0 , ∂a∂t

< 0

II.PDF‐basedSATURATIONADJUSTMENT

€

Δqt

Aqt>0

€

Q > 0 , ∂a∂t

> 0

AT>0

€

Q < 0 , ∂a∂t

< 0

BULKvsPDF‐basedApproach

€

a(U) =U −Uc

1−Uc

2

€

Δqtqs,w

=1−Uc

€

a(U) = ...

0.88 0.9 0.92 0.94 0.96 0.98 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

RH vs a

RH

a

CAM35

CAM40

0.88 0.9 0.92 0.94 0.96 0.98 10

2

4

6

8

10

RH vs G of PDF

RH

G

€

Uclr =U − a1− a

=(1−Uc ) a +Uc − a

1− a

€

Uclr(a→1) =1+Uc

2

€

Uclr =U − a1− a

= ......

€

Uclr(a→1) =1

ConsistencybetweenCloudFracKonandIn‐CloudLWC

•  Forcethelayeratp=900[hPa],T=280[K],qv=6.84[gkg‐1],ql=0.16[gkg‐1],a=0.6,∆p=20[hPa]withvariousexternalforcingsoftemperature(AT)andwatervapor(Aqv)

•  Examine‘Q’and‘∆avs∆ql,cloud’.

•  TestforBulkandPDF‐basedapproachwithahalfwidthoftotalspecifichumidity=0.1*qs(T,p)correspondingtoUc=0.9.

ConvecKon

RadiaKon

PBLProcess

Dynamics

Macro‐Microphysics

ConvecKons CAM3 CAM35

EquilibriumCAM35=CAM4

3DifferentConfiguraKonsofBulkSaturaKonAdjustments

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Toolargein‐cloudLWCcomparedtocloudfracKon

VerKcalCloudOverlap

x

x

MaximumOverlap

€

Δz

€

a1 = 0.5

€

a2 = 0.5

€

amax,overlap = 0.5

x

x

MinimumOverlap

€

amin,overlap = 0

x

x

RandomOverlap

€

aran,overlap = 0.25

€

aoverlap = λ ⋅ amax,overlap + (1− λ) ⋅ aran ,overlap

€

λ = exp(−Δz /2000)

Cloud

TopInterface

BaseInterface

PrecipitaKon

MaximumOverlap

:Aerosol :CloudDroplet :PrecipitaKonDroplet

ParameterizaKonof’CloudOverlapStructure’

hasdirectinfluenceson

ProducKonofPrecipitaKon

EvaporaKonofPrecipitaKon

DeposiKonofAerosolAerosolIndirectEffect

RadiaKon

etc.(wetchemistry…)

ClearSky

PrecipitaKon

MinimumOverlap

•  Cumulus

•  RH(RelaKveHumidity)Stratus

•  KH(Klein‐Hartmann)Stratus

€

as,KH = f (S) , S ≡θv (700) −θv (1000)

3CloudTypesinCAM3

€

ac = f (M) , M : ConvecKveUpdratMassFlux

€

as,RH = f (RH) , RH : Grid‐MeanRelaKveHumidity

:Cumulus

:RHStratus

:RHStratus+Cumulus

:RHStratus+KHStratus

:KHStratus :KHStratus+Cumulus

:Cumulus

:RHStratus=Stratus

HorizontalGeometryofCloudsinCAM

CAM35 CAM4

VerKcalCloudOverlapinCAM

• RadiaKon(SWandLW)• Combine‘cumulus’and‘stratus’into‘onesinglecloud’ineachlayer.• MaximumoverlapineachofthreeregionsrepresenKngthelower,middle,anduppertroposphereandrandomoverlapbetweentheseregions.

• ConvecKon(deepandshallowconvecKons)• WheneverconvecKveprecipitaKonfluxisposiKve,convecKveprecipitaKonareais1.

• StraKformMicrophysics• StratusismaximallyoverlappedwithstraKformprecipitaKonarea.

• WetDeposiKonofAerosol• UseaddiKonaloverlappingassumpKonsdifferentfromtheabove….

WeneedtouseaunifiedverKcalcloudoverlapstructureforallschemesbyconsideringdifferentverKcaloverlappingnaturesofcumulusandstratus.

• Cumulusisnothorizontallyoverlappedwithstratusinasinglelayer.

• CumulushasitsownLWCdifferentfromtheLWCofstratus.CumulusandstratushavedifferentradiaKveproperKes.

• CumulushasadifferentverKcaloverlappingstructurefromstratus:CumulusismaximallyoverlappedwithcumulusregardlessofverKcalseparaKondistance.

UnifiedCloudOverlappingScheme

•  HorizontalGeometry

–  ‘Cumulus’and‘Stratus’arenon‐overlapped

•  VerKcalGeometry

–  Cumulus:‘Maximally’overlapped

–  Stratus:‘Randomly’overlapped

OverlappingAreaBetween‘ConvecKvePrecipitaKonArea’and‘StratusCloudFracKon’

€

a sc =

iN

⋅

i= imin

imax

∑ P(i)PTOT

€

imin = max(0,max(N ⋅ ac − n ,0)− N ⋅ ar )

€

imax = min(N ⋅ as ,N ⋅ ac − max(n − N ⋅ am ,0))

€

P( i) = N ⋅asCi( ) ⋅ N ⋅ac

Pi( ) ⋅ N ⋅acCj( ) ⋅ N ⋅am

Pj( ) ⋅ N ⋅ac −iPN ⋅ac −j( ) ⋅ N −N ⋅ac −j

PN ⋅as −i( )[ ]j=jmin

jmax

∑

⋅ N ⋅ar

PN ⋅ar( )

€

jmin = max(N ⋅(ac − ac )+ i,0)

€

jmax = min(N ⋅ ac ,N ⋅ am ,N ⋅(1− ac − as)+ i)

WesternPacificWarmPool(6.6oN,100oE).ANN.

0 0.1 0.2 0.3 0.4

100

200

300

400

500

600

700

800

900

Cloud Fractions

[ fraction ]

[ hP

a ]

Cumulus

Stratus

0 0.1 0.2 0.3

100

200

300

400

500

600

700

800

900

In!Cloud LWC+IWC

[ g kg!1

]

[ hP

a ]

Cumulus

Stratus

0 0.5 1

100

200

300

400

500

600

700

800

900

Precipitation Areas

[ fraction ]

[ hP

a ]

Convective

Stratiform

Mixed

CAM4

0 0.2 0.4 0.6

100

200

300

400

500

600

700

800

900

Precipitation Fluxes

[ mm day!1

]

[ hP

a ]

Convective

Stratiform

Mixed

Total

0 0.1 0.2 0.3 0.4

100

200

300

400

500

600

700

800

900

Production of Precipitation

[ g kg!1

day!1

]

[ hP

a ]

Convective

Stratiform

Total

0 0.02 0.04 0.06

100

200

300

400

500

600

700

800

900

Evaporation of Precipitation

[ g kg!1

day!1

]

[ hP

a ]

Convective

Stratiform

Mixed

Total

ToostrongevaporaKoninCAM!

SUMMARY

I.  ParameterizaKonofSymmetricTurbulence•  DryTurbulenceScheme(CAM3PBL)

•  MoistTurbulenceScheme(CAM4PBL)•  TreatmentofelevatedsourceofTKEassociatedwithcloudsuccessfulsimulaKonofcloud‐toppedPBLaswellasdrystableanddryunstablePBL

II.  CloudMacrophysics•  NetCondensaKonRateofWaterVaporintoCloudLiquid(Q)

•  BulkSaturaKonAdjustment•  PDF‐BasedSaturaKonAdjustment

•  CloudFracKon(a)•  QuadraKcformulaofa(U)•  a(U)fromthePDF‐basedapproach•  ConsistencybetweencloudfracKonandin‐cloudLWC

•  VerKcalOverlapofCloudFracKon•  Unifiedcloudoverlappingschemeforsimultaneoustreatmentofcumulusandstratus

ResponseofMSCtoincreasingSST

RadiaOvecooling&Entrainmentdrying

LCL

SEL

ColdSST

ReducedradiaOvecooling&Enhancedentrainmentdrying

ElevatedSEL

TurbulenceSuppression(decoupling)

WarmSST

TransiKonofMBLfromwell‐mixedstratocumulustothedecoupledstate.

Deepening‐DecouplingandDissipaKonofStratocumulus

ColdSST WarmSST

Cumulusdevelops

Morning MidAternoon

EPIC.2001.Oct.

Stratocumulus–SWRadiaKonDiurnalCycle