Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 9, 4039-4052, 2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
19 Jun 2009
How important is the vertical structure for the representation of aerosol impacts on the diurnal cycle of marine stratocumulus?
I. Sandu1,2, J.-L. Brenguier1, O. Thouron1, and B. Stevens2,3
1CNRM-GAME, Meteo-France/CNRS, Toulouse, France
2Max Planck Institute for Meteorology, Hamburg, Germany
3University of California at Los Angeles, Los Angeles, CA, USA

Abstract. Large-Eddy Simulations (LES) are performed to examine the impact of hygroscopic aerosols on the diurnal cycle of marine stratocumulus clouds, under varying meteorological forcing conditions. When the cloud condensation nuclei concentration increase is sufficient to inhibit drizzle formation in the cloud layer, the precipitating and the non-precipitating cloud layers exhibit contrasting evolutions, with noticeable differences in liquid water path. Aerosol-induced modifications of the droplet sedimentation and drizzle precipitation result in noticeable changes of the entrainment velocity at cloud top, but also in significant changes of the vertical stratification in the boundary layer. This set of simulations is then used to evaluate whether a model which does not explicitly represent the effects of the interactions occurring within the boundary layer on its vertical stratification (i.e. such as a mixed-layer model) is capable of reproducing at least the sign, if not the amplitude, of these aerosol impacts on the liquid water path. It is shown that the evolution of the vertical structure is key to the responses we simulate, and must be considered in bulk models that wish to predict the impact of aerosol perturbations on the radiative properties of stratocumulus-topped boundary layers.

Citation: Sandu, I., Brenguier, J.-L., Thouron, O., and Stevens, B.: How important is the vertical structure for the representation of aerosol impacts on the diurnal cycle of marine stratocumulus?, Atmos. Chem. Phys., 9, 4039-4052, doi:10.5194/acp-9-4039-2009, 2009.
Search ACP
Final Revised Paper
Discussion Paper