Modeling radiation and convective structures in stratocumulus clouds with simultaneous consideration of aerosol effects
Duration: 1 July 2007 – 30 June 2010
Develop a fine scale 3-D LES-Model to simulate stratiform boundary layer clouds with an aerosol dependent microphysic that should be coupled to the 3-D radiative transfer code SHDOM in order to quantify the bias between 1D simulations and actual horizontally heterogeneous clouds.
A simple approach for microphysics has been implemented in the compressible 1D-3D LES-Model ASAM. Some Simulations have been made to compare the results with the work from Bjorn Stevens [Stevens, 2006] and measurements by Hoken et al. [Hoken, et al. 2004]
Simulation has been done with a 100×50 cell domain with a horizontal spacing of 50m and a vertical gridstep of 100 m. So the modeldomain reaches up to 5 km. Startvalues and boundaryconditions were taken from [Stevens, 2006]
Summary and Outlook
The profiles for Theta and Qv are quite similar to the ones from [Stevens, 2006] but the vertical dimension of the boundarylayer is not that high and the maximum of qc is at a much higher level near the top of the cloudlayer. The profile of qc seems more like the measured one of Hoken. This can be explained through the differences in the microphysical parameterisation. In the model ASAM it takes some time to condese all the watervapor what happens instantanously in the model by Stevens.
This will be the point of interest for future research. The aim is to alter these microphysical parameterisations to fit the measurements and to implement aerosol- and radiation-influences and to do these calculations in 3D.
Stevens, B., “On the Growth of Layers of Nonprecipitating Cumulus Convection”, Journal of the Atmospheric Sciences, 2006
Hogen, R.J., Gaussiat, N., Illingworth, A.J., “Stratocumulus Liquid Water Content from Dual-Wavelength Radar”, J. Atmos. Oceanic Technol., 2004