Numerical modelling of microburst with Large-Eddy Simulation
1Departamento de Fisica, Universidade Federal de Santa Maria, Santa Maria, RS, Brasil
2Institute of Atmospheric Sciences and Climate, CNR/ISAC, Lecce, Italy
Abstract. An isolated and stationary microburst is simulated using a 3-D time-dependent, high resolution Large-Eddy Simulation (LES) model. The microburst downdraft is initiated by specifying a simplified cooling source at the top of the domain near 2 km. The modelled time scale for this damaging wind (30 m/s) is of order of few min with a spatial scale enclosing a region with 500 m radius around the impact point. These features are comparable with results obtained from full-cloud models. The simulated flow shows the principal features observed by Doppler radar and others observational full-scale downburst events. In particular are observed the expansion of the primary and secondary cores, the presence of the ring vortex at the leading edge of the cool outflow, and finally an accelerating outburst of surface winds.
This result evidences the capability of LES to reproduce complexes phenomena like a Microburst and indicates the potential of LES for utilization in atmospheric phenomena situated below the storm scale and above the microscale, which generally involves high velocities in a short time scale.