Irina Sandu, JeanLouis Brenguier, Olivier Geoffroy

1
CNRM/GMEI/ MNPCA
Ambiguous results of Large-Eddy Simulations of
marine stratocumulus clouds

• Irina Sandu, Jean-Louis
  Brenguier, Olivier Geoffroy

Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
2
CNRM/GMEI/ MNPCA
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
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
3
CNRM/GMEI/ MNPCA
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
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
4
I.
Boundary layer clouds marine stratocumulus
Considerable coverage optical properties
Negative radiative forcing r
significant impact on the planetary radiative
budget
Complexe interaction between dynamics -
microphysics - radiation
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
5
I.
the indirect effects of aerosols
1st indirect effect
2nd indirect effect
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
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
Set-up of the simulations for different cases of
marine stratocumulus clouds
III. Analysis of the results
IV. Conclusions
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
7
Méso-NH as a LES code
II.
set of parametrisations adequate and coherent
Complexe interaction dynamics microphysics -
radiation
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
8
II.
Large-Eddy Simulations of different cases of
marine stratocumulus
36 hours simulations initialized with various CCN
concentrations, for several large scale forcings

the impact of CCN on the stratocumulus capped
boundary layer evolution for a time scale longer
then one diurnal cycle
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
9
CNRM/GMEI/ MNPCA
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
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
10
W6 subsidence w - 6X10-6 z (m/s) Nccn
50, 200, 600 cm-3 no large scale
advection
Nc 40, 120, 220 cm-3
11
LWP (g/m2)
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 40, 120, 220 cm-3
12
? budget 50cm-3
700 m
? budget 600cm-3
700 m
9 12 LT
9 12 LT
CB 9LT
CB
Cloud Droplets evaporation
Cloud Droplets evaporation
Radiative heating
Radiative heating
Drizzle evaporation
Vertical advection
Vertical advection
13
W6 subsidence w - 6X10-6 z (m/s) Nccn
50, 200, 600 cm-3 no large scale
advection
Nc 40, 120, 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
Set-up of the simulations for different cases of
marine stratocumulus clouds
III. Analysis of the results
IV. Conclusions
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
15
IV.
Conclusions
for specific initial conditions the system
response is not unique
strong coupling between dynamics - microphysics
- radiation
the system response to an increase of the cloud
droplet concentration reverses from the first
diurnal cycle to the next one
the trap of 1st order hypotheses !
16
Questions?
17
Validation of the code LES
II.
FIRE I case study (1987) - intercomparison
exercice during EUROCS
Joint GCSS-GPCI/BLCI-RICO Workshop , NASA/GISS
New York USA, 18-21 September 2006
18
Validation of the code LES
II.
FIRE I case study (1987) - intercomparison
exercice during EUROCS
Meeting on the Parametrisation of Boundary Layer
Clouds , Toulouse, 3rd 4th July 2006
19
II.
Validation du code LES
Le cas FIRE (1987) - exercice d'intercomparaison
EUROCS
Meeting on the Parametrisation of Boundary Layer
Clouds , Toulouse, 3rd 4th July 2006
20
mm/jour
21
LWP (g/m2)