Olivier Geoffroy Parameterization of precipitation in boundary layer clouds at the cloud system scale Pier Siebesma, Roel Neggers RK science lunch, 05/10/2010

Olivier GeoffroyOlivier Geoffroy

Parameterization of precipitation in boundary layer clouds at the cloud system

scale

Pier Siebesma, Roel Neggers

RK science lunch, 05/10/2010

Microphysical processes

w

CCN : D ~ 0.01-10 µm

D40 µm

n(D)

Cloud droplets : ~ 1 µm < D < ~ 40 µm

CCN Activation


Condensation

w

CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1


CCN Activation


Condensation

w

CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1


CCN Activation

Mixing

D40 µm

n(D)


Condensation

w

CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1


CCN Activation

Cloud droplet sedimentation

Mixing

D40 µm

n(D)



Condensation

w

precipitation embryo D ~ 40 µm


CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1

Collection

D40 µm

n(D) ECS

CCN Activation

Collection : Efficient for D > 40 µm (Bartlett, 1970)

Mixing

D40 µm

n(D)



Condensation



CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1

Collection

D40 µm

n(D) ECS

CCN Activation


Mixing

D40 µm

n(D)

Polluted cloudw

precipitation efficiency (?)

LWP (? (feedbacks))

(2nd aerosol indirect effect)


Condensation

w

CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1


CCN Activation


Mixing

D40 µm

n(D)

Marine cloud



Condensation

w



CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1

Collection

D40 µm

n(D) ECS

CCN Activation


Mixing

D40 µm

n(D)


Condensation

w


CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1

Collection

D40 µm

n(D) ECS

Rain drops ~ 40 µm <D < 100-500 µm



CCN Activation

Mixing

D40 µm

n(D)

Growth depends on the available amount of water i.e. H or LWP


Condensation

w



CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1

Mixing

D40 µm

n(D)

Collection

D40 µm

n(D) ECS



CCN Activation

Rain sedimentation


Condensation



CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1

Mixing

D40 µm

n(D)

Collection

D40 µm

n(D) ECS



CCN Activation

Rain sedimentation size sorting

Rain evaporation


Condensation



CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1

Mixing

D40 µm

n(D)

Collection

D40 µm

n(D) ECS



CCN Activation


Rain evaporation


Condensation



CCN : D ~ 0.01-10 µm

D40 µm

D40 µm

n(D)

n(D)

Ddt

dD 1

Mixing

D40 µm

n(D)


Collection

D40 µm

n(D) ECS



CCN Activation

Rain evaporation

Objective

- Development of a precipitation scheme for boundary layer clouds at the GCM scale

Precipitation in a key process in BLC evolution. Low cloud regimes and transitions between regimes Earth radiation budget, general circulation, hydrological cycle.

Quantification of the aerosol indirect effect.

explicit or bin

D

n(D)

Bulk

Cloudrain

D

D0

n(D)

Autoconversion

AccretionSelf-collection Self-collection

2 bins 4 collection processes

Collection processes :Stochastic Collection Equation (SCE)

LES collection schemes

Cloud

rain

Cloud :qc (g kg-1)

Nc (cm-3)

Rain :qr (g kg-1)

Nr (cm-3)

Measured spectra

D0 ~ 40 - 100 µm

D0

Cloud

rain

D (μm)

Autoconversion

Cloud :qc (g kg-1)

Nc (cm-3)

Rain :qr (g kg-1)

Nr (cm-3)

Precipitation formation, autoconversion rate

TresholdNqfkt

qccautoauto

r )()(

Khairoutdinov and Kogan (2000)

2.47 -1.79

Beheng (1994)4.7 -3.3Seifert and Beheng (2001)

4 -2

Tripoli and Cotton (2000)

2.33 -0.33

α β

Kessler (1969)1

Treshold

H(qc-qtreshold)

Sundqvist (1978)1

Liu and Daum (2006)2.33 -0.33

2)exp(1treshold

c

q

q

H(r6-rtreshold)

H(rv-rvtreshold)

Naerosol

Highly non linear

0

0

1

1

1

Auto rate

qc

Aerosol indirect effect dependance in Nc necessary

Nc

Nc

Accretion

rcaccraccrr qqkt

q

)(

Depends on local values

Autoconversion / accretion rates mean profiles (12H) in cumulus

Only in cloud core

- Formation of precipitation in cloud core-Accretion = ~ 10 x autoconversion

-Simulations show larger accretion rate for wup-vqr > 0(drops go upward)

Only in cloud core

auto accr

wup-vqr > 0

wup-vqr < 0

vqr

wup

accr

))exp(1(0015.0)( 2

treshold

ccauto

r

q

qq

t

q

Autoconversion:

Frac=cste

0 overlap, Sundqvist (1978) scheme

w=wup(k-1)

qc=lup(k)

1

)(

)()(

kauto

rc

cupauto

qauto

c

w

z

t

qq

z

qw

z

F

t

qc

=cste?

New scheme

bc

acauto

c Nkqt

q

)(

Autoconversion:

Frac=cste

w=wup(k-1)

qc=lup(k)

cupqr qwF

New scheme, accretion regimeAccretion:

Frac=cste

rccollqr

ser

accrr

qqkz

Ft

q

t

q

0)()( dim

7.004.0 qrr Fq

(From RICO in situ measurements)

3.0/13.01 ))(( kck FzkqF

autoF

New scheme, overlap

Frac=cste

k+1

k

))/hz-(z-(1 oktopk

zk

ho

kkkclear 1

ztop

3.0/13.01 ))(( kckk FzkqF

?

Autoconversion formulation

paramr

t

q)(

coreautor

t

q

)(

(kg kg-1 s-1)

(kg kg-1 s-1)

LES simulations (12H)- RICO, moister RICO - Nc= 40, 50, 70, 100, 200 cm-3

- Seifert and Beheng (2006) scheme:

Identification of individual clouds and average clouds

of same height

coreautor

t

q

)(

corecq

power law hypothesis:

c

coreccoreauto

c

N

qa

t

q

)(

0027.0

44.2

56.3

a

& regression

autoLES = f(autoparam)

1/1 line

))1(

)(1(~)(

22

42006

c

cSBc

N

q

t

qauto

37.07.0 )1(~)(

Horizontal mean values of:

rc

c

qq

q

1

SCM results

LWP, rain flux at surface, Nc=50, 70, 100, 200 cm-3

50 cm-3

70 cm-3

200 cm-3

No rain

100 cm-3

LWP:

precipitation at surface:

60 g m-2

= 25 Wm-2 ~ 0.4 mm h-1 ~ 10 mm j-1 50 cm-3

70 cm-3 100 cm-3

200 cm-3

rain flux profilesNc=50, 200 cm-3

Nc = 50 cm-3

Nc = 200 cm-3

Autoconversion time scale

w=5ms-1

w=1ms-1

w=wup

w

z

t

qq

z

qw

z

F

t

q

autor

c

cupauto

qauto

c c

)(

)()(

w=5ms-1w=1ms-1

w=wup

Sensitivity to the overlap

h0=1000

h0=600

h0=300LWPNc = 50 cm-3

h0=300

h0=600

h0=1000

- Developpment and implementation of a precipitation scheme in ECMWF SCM model coupled with the DualM scheme.- Possibility to take in account the shear effect- Possible to take in account interaction between precipitation flux and the stratiform component of the cloud (for Sc).

- Dependency in NCCN

Test of the scheme using the KPT and half a year of precipitation flux and CCN concentration measurements:

Conclusion and perpective

North North SeaSea

originsorigins

Dust Dust episodeepisode

CCN concentration at Cabauw during IMPACT (May 2008)

Regional backgroundRegional background Regional Regional backgroundbackground

Sundqvist no evap SB, no evap, Nc 70

lwp

lwp

Rsurf

Rsurf

Sundqvist no evap SB, no evap, Nc 50

lwp

lwp

Rsurf

Rsurf

SB, evap2, Nc 70

lwp

RsurfRsurf

SB, evap2, Nc 200

lwp

Rsurf

h0=300, 500, 800, 1500, SB, Nc 50, evap2

lwp lwp

lwp

lwp

h0 300 m h0 500 m

h0 800 m h0 1500 m

SB, Nc 50, original evap

lwp

auto2, Nc 50, original evap

auto2, Nc 50, evap2

SB, evap2, Nc 50

lwp

Rsurf

Nc 50 cm-3 Nc 70 cm-3

Nc 200 cm-3

lwp lwp

lwp

auto 2 (a=2.74, b=-1.35)

Param accr up + auto w0=5 ms-1

10e-6

aqr=1.85 bNc=1.17

Param accr up + auto w0=5 ms-1

2.5e-6

LWP, rain flux at surface, Nc=50, 70, 100, 200 cm-3

50 cm-3

70 cm-3

200 cm-3

No rain

100 cm-3

LWP:

precipitation at surface:

60 g m-2

= 25 Wm-2 ~ 0.4 mm h-1 ~ 10 mm j-1 50 cm-3

70 cm-3 100 cm-3

200 cm-3

5 Wm-2

Steady state:

accrautoz

qrwv

z

F

sedaccrauto

upqrqr

)(

0

wup-vqr < 0 wup-vqr > 0

Documents

Olivier Geoffroy Parameterization of precipitation in boundary layer clouds at the cloud system scale Pier Siebesma, Roel Neggers RK science lunch, 05/10/2010