Investigations on in-cloud turbulence effects on drop growth and precipitation formation
Responsible: Theres Riechelmann geb. Franke
Project type: ​DFG research project within the priority programme ​MetStröm with ​RWTH Aachen and ​KIT
Duration: 01/02/2008-31/01/2014

The project addresses an intensively discussed problem of cloud microphysics, namely the effect of an in-cloud turbulent flow field on droplet growth and precipitation formation. The questions to be answered are: Which influence has the local cloud turbulence on the collision efficiency of small cloud droplets and thus on the coagulation function where the latter is an important ingredient for numerical simulations of precipitation development? What is the impact of turbulence on cloud microphysics compared to the traditional approach disregarding this effect?

Referring to the study PALM is used to perform high-resolution large-eddy simulations of three-dimensional convective clouds in which a large number of water droplets (Lagrangian droplets) is simulated explicitly. The focus is on the spatial and temporal evolution of the droplet spectrum, the spatial distribution of the droplet concentration and the water droplet tracks within turbulent clouds.

Animations of three-dimensional convective clouds can be found in our gallery.

Project-related Publications:

• Kunnen, R. P. J., C. Siewert, M. Meinke, W. Schröder and K. D. Beheng, 2013: Numerically determined geometric collision kernels in spatially evolving isotropic turbulence relevant for droplets in clouds. Atmos. Res., 127, 8-21, doi: ​10.1016/j.atmosres.2013.02.003

• Riechelmann, T., Y. Noh and S. Raasch, 2012: A new method for large-eddy simulations of clouds with Lagrangian droplets including the effects of turbulent collision. New J. Phys., 14, ​065008, doi: ​10.1088/1367-2630/14/6/065008.