1

Irina Sandu , Jean-Louis Brenguier, Olivier Geoffroy

CNRM/GMEI/ MNPCA

2

CNRM/GMEI/ MNPCA

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

I. Introduction

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

Méso-NH as a LES code

Validation on FIRE-I case

III. Large-Eddy simulations of different cases of marine stratocumulus

IV. Conclusions

3Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

CNRM/GMEI/ MNPCA

I. Introduction

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

Méso-NH as a LES code

Validation on FIRE-I case

III. Large-Eddy simulations of different cases of marine stratocumulus

IV. Conclusions

4

Considerable coverage + optical properties

10~.

océan

Sc

A

A

Complexe interaction between dynamics - microphysics - radiation

Negative radiative forcing r

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

5

Twomey (1977): LWP constant NCCN Nc albedo

Albrecht (1989): NCCN Nc re

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

Suppression of drizzle

formation

The cloud life time

LWP constant

6

CNRM/GMEI/ MNPCA

I. Introduction

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

Méso-NH as a LES code

Validation on FIRE-I case

III. Large-Eddy simulations of different cases of marine stratocumulus

IV. Conclusions

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

7

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 lengthAdvection scheme – positively defined second order centered scheme

Microphysics – Khairoutdinov &Kogan 2000 (O. Geoffroy )

– 2 moments bulk scheme developed for Sc.

Radiative code (ECMWF) – coding problems: the cloud overlap (O. Thouron)

LW – Savijarvi (1997) • cloud optical

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

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

8

The initialisation followed the intercomparison exercice (Duynkerke et al. 2004)

•2.5kmX2.5kmX1.2km – 50mX50mX10m

• initial profiles

•Subsidence w=-1x10-5 x z m/s

•Forcings on L et qT (large scale advection)

•No precipitations

L et qT

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

0.7g/kg

0LT 12LT 0LT 12LT

700mrc(g/kg)

0LT 12LT 0LT 12LT

LWP (

g/m

2)

250g/m2

11

CNRM/GMEI/ MNPCA

I. Introduction

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

Méso-NH as a LES code

Validation on FIRE-I case

III. Large-Eddy simulations of different cases of marine stratocumulus

IV. Conclusions

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

12

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

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

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

13

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

14

CNRM/GMEI/ MNPCA

I. Introduction

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

Méso-NH as a LES code

Validation on FIRE-I case

III. Large-Eddy simulations of different cases of marine stratocumulus

IV. Conclusions

Meeting on the Parametrisation of Boundary Layer Clouds , Toulouse, 3rd – 4th July 2006

15

16