Large-Eddy Simulation of a microburst

The three-dimensional structure and evolution of an isolated and stationary microburst are simulated using a time-dependent, high resolution Large-Eddy-Simulation (LES) model. The microburst is initiated by specifying a simplified cooling source at the top of the domain around 2 km a.g.l. that leads to a strong downdraft. Surface winds of the order of 30 m s-1 were obtained over a region of 500 m radius around the central point of the impinging down- draft, with the simulated microburst lasting for a few min- utes. These characteristic length and time scales are consis- tent with results obtained from numerical simulations of mi- crobursts using cloud-resolving models. The simulated flow replicated some of the principal features of microbursts ob- served by Doppler radars: in particular, the horizontal spread of strong surface winds and a ring vortex at the leading edge of the cold outflow. In addition to the primary surface outflow, the simulation also generated a secondary surge of strong winds that appears to represent a pulsation in the mi- croburst evolution. These results highlight the capability of LES to reproduce complex phenomena like microbursts, indicating the poten- tial usage of LES models to represent atmospheric phenom- ena of time and space scales between the convective scale and the microscale. These include short-lived convectively- generated damaging winds.