Lab Home | Phone | Search
Center for Nonlinear Studies  Center for Nonlinear Studies
 Home 
 People 
 Current 
 Affiliates 
 Visitors 
 Students 
 Research 
 ICAM-LANL 
 Publications 
 Conferences 
 Workshops 
 Sponsorship 
 Talks 
 Colloquia 
 Colloquia Archive 
 Seminars 
 Postdoc Seminars Archive 
 Quantum Lunch 
 Quantum Lunch Archive 
 CMS Colloquia 
 Q-Mat Seminars 
 Q-Mat Seminars Archive 
 P/T Colloquia 
 Archive 
 Kac Lectures 
 Kac Fellows 
 Dist. Quant. Lecture 
 Ulam Scholar 
 Colloquia 
 
 Jobs 
 Postdocs 
 CNLS Fellowship Application 
 Students 
 Student Program 
 Visitors 
 Description 
 Past Visitors 
 Services 
 General 
 
 History of CNLS 
 
 Maps, Directions 
 CNLS Office 
 T-Division 
 LANL 
 
Monday, January 25, 2010
11:00 AM - 12:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Seminar

Building resolving simulations in the Weather Research and Forecasting model

Katie Lundquist
University of California at Berkeley / LLNL

Mesoscale models, such as the Weather Research and Forecasting (WRF) model, are increasingly used for high resolution simulations, particularly in complex terrain. Terrain-following coordinates employed by mesoscale models are mapped to the terrain, which simplifies the application of lower boundary conditions. The signature of the topography causes distortion of computational cells in the transformed coordinate system. With steep terrain or high computational resolution, the distortion can be extreme in the near surface region, and often extends as high as the troposphere. This grid skewness introduces numerical truncation errors, which can significantly degrade the accuracy of the solution. This loss of fidelity is demonstrated using a test case of a scalar cloud advecting over highly variable topography.

Use of an alternative gridding technique, known as an immersed boundary method, alleviates coordinate transformation errors and eliminates restrictions on terrain slope which currently limit mesoscale models to slowly varying terrain. Simulations are presented for canonical cases with shallow terrain slopes, and comparisons between simulations with the native terrain-following coordinates and those using the immersed boundary method show excellent agreement. Additionally, surface fluxes of heat and moisture complicate treatment of the immersed boundary. Realistic surface forcing can be included at the immersed boundary by atmospheric physics parameterizations, which are modified to include the effects of the immersed terrain.

Using the immersed boundary method, WRF is capable of simulating highly complex terrain, as demonstrated by validation cases and preliminary simulations of flow over urban terrain. In order to demonstrate the ability of the IBM-WRF code to simulate atmospheric flow around complex structures, we will present results from building resolving simulations in urban environments. Specifically, flow and dispersion are demonstrated for terrain in the Mock Urban Setting Test (MUST) and for the Joint Urban 2003 field campaign in Oklahoma City.

Host: Xylar Asay-Davis