'''Large-eddy simulations of thermally-induced circulations in the convective boundary layer''' \\
Responsible: Marcus Oliver Letzel \\
Project type: Diplomarbeit (equivalent to master thesis) \\
Duration: 06/01/2000 - 13/02/2001 \\\\
Mesoscale circulations induced thermally by differential boundary layer heating due to surface inhomogeneities on scales of 10 km and more can significantly affect the average profiles and the structure of the atmospheric boundary layer. The inhomogeneities studied were one-dimensional and were represented in the model by sinusoidal surface heatflux variations. The results of this numerical study suggest that mesoscale circulations may considerably impede the typical quasi-steady convective boundary layer development. The circulations are affected - often nonlinearly - by a number of parameters: Mean surface heatflux, perturbation wavelength and amplitude, subsidence rate, background wind magnitude and direction as well as the geographical latitude. The simulated mesoscale circulations were periodic, but asymmetric, which clearly shows up in form of higher wavenumber peaks in the power spectra of velocity and temperature. Vertical profiles and time series demonstrate that the onset of the mesoscale circulation triggers off a temporal boundary layer oscillation, whose period is proportional to the time that the inhomogeneous surface heatflux information takes to be advected from its minimum to its maximum and whose amplitude decreases with time due to friction. (See also the follow-up study by [../2001_04 Herold] and the studies by [../2001_03 Schröter] and [../2002_01 Uhlenbrock].)