Genesis and Features of Dust Devil-Like Vortices in Convective Boundary Layers - A High Resolution Study using Large-Eddy Simulations
Small-scale, short-lived, convective vortices with a vertical axis of rotation, which visually appear through the swirling of particles such as dust, are called dust devils. This phenomenon occurs mainly above dry ground during high-pressure conditions with low or moderate background wind and strongly superadiabatic temperature gradients close to the ground. Apart from the visually impressive appearance, dust devils are particularly interesting because of their influence on the vertical transports of dust and heat within the boundary layer. In addition, wind velocities of more than 10 m s-1 and sudden wind direction changes caused by dust devils result into a hazard for the environment, e.g. for aviation. Therefore, these vortices have been intensively observed, measured and experimentally or numerically investigated since the 20th century. Beside characteristic features such as diameter, height or lifetime, the genesis and maintenance of dust devils is often discussed. Additionally, the quantification of vertical transports plays an important role in order to better estimate the significance of dust devils for the weather and climate. The project presented here shall provide new insights in all the research fields mentioned above and shall support or disprove established theories. It is funded and was reviewed by the German Research Foundation (DFG). Furthermore, the project is done in cooperation with the working group Ilmenauer Fass of the Technische Universität Ilmenau who are responsible for the experimental research work. In contrast, the numerical investigations are carried out from Hanover using the model PALM (PArallelized Large-eddy simulation Model). PALM has been developed for many years at the institute of meteorology and climatology and is able to perform turbulence-resolving simulations.