Gaudet, Brian, The Pennsylvania State University, and
Aijun Deng, David Stauffer, and Nelson Seaman, The Pennsylvania State
University
The WRF-ARW model is
capable of physically representing the effects of turbulence in two distinct
ways. One way involves using
parameterizations of the effects of turbulence on the mean state variables
found within the boundary layer schemes of the physics module. These are typically used when the
horizontal grid spacing is significantly greater than the scale of the
energy-containing eddies. The
other way is to run WRF-ARW in large eddy simulation (LES) mode, in which the
energy-containing turbulent eddies are explicitly resolved, while the downscale
cascade of turbulent eddies is accounted for by a subgrid
parameterization. WRF-LES can be
used in a nested grid configuration, with a parent grid that uses a turbulence
parameterization and realistic heterogeneous atmospheric and surface
conditions, and nested grids using LES closure; however, non-periodic nested
LES domains can suffer from deficient or unrealistic eddy structures near the
lateral boundaries.
In this presentation we
will show how nested WRF-LES non-periodic domains can be improved through the
use of an Ôeddy seedingÕ method, using a library of stored eddy structures and
appropriate scaling methods.
Comparisons will be shown with simulations using a version of the CM1
LES code that demonstrates the new method. Future possible refinements of the method will also be
discussed.