Development and evaluation of high resolution simulation tools to improve fire weather forecasts

Fire weather forecasts rely on numerical weather simulations where the grid size is 4 km x 4 km or larger. In areas of complex terrain, this model resolution will not capture the details of wind flows associated with complicated topography. Wind channeling in valleys, wind speed-up over mountains and ridges, and enhanced turbulence associated with rough terrain and tall forest canopies are poorly represented in current weather model applications but are important to predicting fire behavior. In this paper, we give an overview of a new a research program to collect detailed wind data for three very different types of terrain/landcover features and to use these data to evaluate and improve high resolution simulation tools for fire weather forecasts. The field sites will include a low vegetation steep canyon, a large isolated terrain obstacle (Big Southern Butte, ID), and a mature forested mountain/valley drainage. At each site, a dense array of surface wind sensors, complemented with vertical profiling instruments, will be used to map wind fields over an extended period. The data will be used to evaluate a range of high-resolution wind models that can be used to enhance current fire weather forecast systems. The high resolution models include: WindNinja, a mass consistent interpolation scheme; WindNinja, enhanced to use a computational fluid dynamics solver; WindWizard, a computational fluid dynamics solver; CALMET as employed in the ClearSky a smoke dispersion forecast system; and WRF-Fire, a fire physics scheme for WRF, developed at the National Center for Atmospheric Research, which includes a fire behavior model with fire/atmosphere dynamic feedback. Preliminary results will be presented from the deployment at the Big Southern Butte site during summer, 2010.