Applied Math/PDE Seminar: Prof George Matheou (Jet Propulsion Laboratory/Caltech/NASA) - Large-eddy simulation of the atmospheric boundary layer

Event Date: 

Friday, May 30, 2014 -
3:00pm to 4:00pm

Event Location: 

  • 4607B South Hall

Event Contact: 

Carlos Garcia-Cervera

Email: cgarcia@math.ucsb.edu

The atmospheric boundary layer, the lowermost (1?"4 km) layer of the atmosphere, is host to a plethora of physical processes that strongly affect the energy balance of Earth, and consequently weather and climate. Large-eddy simulation (LES) is an invaluable technique in the study and prediction of the boundary layer mainly because it can capture detailed flow structure including clouds. In spite of the widespread use of LES, predictions of atmospheric flows lack fidelity. The development of a novel state of-the-art LES framework suitable for the simulation of atmospheric flows is presented. The main components of the LES framework are a high-order fully conservative finite difference discretization and the buoyancy-adjusted stretched-vortex subgrid-scale (SGS) model. The development of a stability correction for the stretched-vortex SGS model is presented. The stability correction accounts of the increasing anisotropy of turbulence motions as stratification increases in a way that is consistent with the physics of stratified turbulence. Moreover, the SGS model employs no flow adjustable parameters. A series of LES runs of diverse meteorological conditions is carried out using identical LES setup (e.g. advection scheme and SGS-model parameters) in order to validate the extension of the model to stratified flows and assess its performance. The analysis of the simulations shows that the new LES framework accurately predicts a diverse set of atmospheric conditions and in all cases the flow statistics exhibit good grid resolution independence, even for resolutions that are typically considered coarse. Grid convergence criteria are also discussed.