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Irina Sandu, Jean-Louis Brenguier, Olivier Geoffroy

CNRM/GMEI/ MNPCA

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

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CNRM/GMEI/ MNPCA

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

I. Introduction

II. Application of the LES technique for studying the indirect effect of aerosols

Méso-NH as a LES code

Set-up of the simulations for different cases of marine stratocumulus clouds

III. Analysis of the results

IV. Conclusions

3

CNRM/GMEI/ MNPCA

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

I. Introduction

II. Application of the LES technique for studying the indirect effect of aerosols

Méso-NH as a LES code

Set-up of the simulations for different cases of marine stratocumulus clouds

III. Analysis of the results

IV. Conclusions

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Considerable coverage + optical properties

10~.

océan

Sc

A

A

Complexe interaction between dynamics - microphysics - radiation

Negative radiative forcing r

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

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Twomey (1977): LWP constant NCCN Nc albedo

Albrecht (1989): NCCN Nc re

Suppression of drizzle

formation

The cloud life time

LWP constant

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

6

CNRM/GMEI/ MNPCA

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

I. Introduction

II. Application of the LES technique for studying the indirect effect of aerosols

Méso-NH as a LES code

Set-up of the simulations for different cases of marine stratocumulus clouds

III. Analysis of the results

IV. Conclusions

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Complexe interaction dynamics – microphysics - radiation

set of parametrisations adequate and coherent

New parametrisation for the single scattering albedo based on aerosol chemical composition for LES modelling of boundary layer clouds

Sandu I., P. Tulet and J.L. Brenguier, Geophys. Res. Lett., 32, L19814, 2005

Turbulence scheme – 3D scheme (Cuxart-2000) – TKE equation +1.5 closure + Deardorff mixing length

Advection scheme – positively defined second order centered scheme

Microphysics – Khairoutdinov &Kogan 2000 (O. Geoffroy )

– 2 moments bulk scheme developed for Sc.

Radiative code (ECMWF) – recent code improvements (O. Thouron)

LW – Savijarvi (1997) • cloud optical

properties SW - Fouquart (1987) not suited for LES of marine stratocumulus

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

Non-hydrostatic model, anelastic system of equations (Lipps and Hemler, 1982)

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36 hours simulations initialized with various CCN concentrations, for several large scale forcings

CCN impact drizzle, the diurnal cycle amplitude, the LWP, the surface and radiative fluxes, the boundary layer energetics

the impact of CCN on the stratocumulus capped boundary layer evolution for a time scale longer then one diurnal cycle

how the system response depends on the external conditions (large scale horizontal advection, subsidence, etc…)

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

Summer situation over Nord-Est Pacific, similar to FIRE I case

Set-up similar to EUROCS intercomparison case (Duynkerke and al. 2004)

2.5kmX2.5kmX1.2km – 50mX50mX10m

Different subsidence rates, large scale advection terms

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CNRM/GMEI/ MNPCA

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

I. Introduction

II. Application of the LES technique for studying the indirect effect of aerosols

Méso-NH as a LES code

Set-up of the simulations for different cases of marine stratocumulus clouds

III. Analysis of the results

IV. Conclusions

10

LW

P (

g/m

2)

0 LT 12 LT 0 LT 12 LT

W6 : subsidence w = - 6X10-6 z (m/s) Nccn= 50, 200, 600 cm-3

no large scale advection

Nc LWP

Nc ~ 40, 120, 220 cm-3

Nc LWP

Drizzle is suppressedCloud droplet sedimentation weakens

Entrainment enhances

Nc re

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LW

P (

g/m

2)

0 LT 12 LT 0 LT 12 LT

W6 : subsidence w = - 6X10-6 z (m/s) Nccn= 50, 200, 600 cm-3

no large scale advection

Nc LWP

Nc LWP

Nc ~ 40, 120, 220 cm-3

W4 : subsidence w = - 4X10-6 z (m/s) Nccn= 50, 600 cm-3

no large scale advection Nc ~ 40, 220 cm-3

subsidence w = - 6X10-6 z (m/s) Nccn= 50, 600 cm-3

1K/day cooling1K

Nc ~ 40, 220 cm-3

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d/dt (K/ h)

50 cm-3

600 cm-3

9 –12 LT

drv/dt (g/kg/h)700 m700 m

9 –12 LT

CB 9LT

12 LT

9 LT

CBCB

700 m

v

budget: 50cm-3

Vertical advection

Radiative heating

Cloud Droplets

evaporation

Drizzleevaporation

700 m budget: 600cm-3700 m

9 –12 LT 9 –12 LT

v

CB

CB

12 LT

9 LT

700 m

Radiative heating

Vertical advection

Cloud Droplets

evaporation

CB

CB 9LTCB

CB 12LT

CB 12LT

700 mTKE (m2/s2)

50 cm-3

600 cm-3

12LT 9LT

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LW

P (

g/m

2)

0 LT 12 LT 0 LT 12 LT

W6 : subsidence w = - 6X10-6 z (m/s) Nccn= 50, 200, 600 cm-3

no large scale advection

Nc LWP

Nc ~ 40, 120, 220 cm-3

Nc LWP

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CNRM/GMEI/ MNPCA

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS New York USA, 18-21 September 2006

I. Introduction

II. Application of the LES technique for studying the indirect effect of aerosols

Méso-NH as a LES code

Set-up of the simulations for different cases of marine stratocumulus clouds

III. Analysis of the results

IV. Conclusions

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