Field evaluation of PB-Piedmont, a mesoscale nighttime smoke dispersion model, for application to Oklahoma landscapes

Prescribed fire is becoming an increasingly used tool in Oklahoma for fuels management, with estimates of between one and two million acres annually being burned. For purposes of smoke management, it is especially important to know where smoke may go during nighttime conditions. If a reliable forecast tool could be developed, fire managers could, for example, forgo a burn on a given morning if it looked like sensitive areas would be smoked out overnight. With respect to wildfires, fire managers could use such a tool to evacuate sensitive areas if necessary. Besides adverse health effects, poor visibility is a concern and can contribute to motor vehicle accidents.

PB-Piedmont is a mesoscale numerical model that was originally developed to simulate and predict nighttime smoke movement near the ground over terrain characteristic of the Piedmont of the southeastern United States. The current model simulates flows (e.g., drainage, synoptic) over complex terrain and utilizes digital elevation data to 30-m resolution. It is initialized with hourly synoptic weather observations and can run with either hourly synoptic data (in a historic, post-burn mode or “nowcast” mode) or with hourly output from the MM5 model (in a forecast mode). Image files of smoke location are output every hour through the period the model is run; screen images are updated every 15 minutes.

Through a research agreement between Oklahoma State University and the Southern Research Station of the USDA Forest Service, PB-Piedmont is now being tested in Oklahoma to see if it is applicable to local landscapes outside the Piedmont region. Much of Oklahoma, with the exception of the plains of the western areas and the mountains in the southeast, has terrain similar to that of the Piedmont.

Three case studies will be presented. One is the case of a local prescribed burn (Marena, Oklahoma) during the afternoon of April 27, 2006. The other two were prescribed burns in the Chickasaw National Recreation Area (National Park Service) near Sulphur, Oklahoma during the afternoons and evenings of March 1 and 2, 2007. With the aid of a GPS unit, “smoke” or “no-smoke” observations were taken by the first author during the nighttime hours by driving local roads surrounding and within the prescribed burn areas. PB-Piedmont was later run in the post-burn, historical mode with hourly synoptic weather data. Comparisons of smoke locations predicted by the model were then made with the actual smoke observations from a given location and time. This presentation will give the results from these three case studies. Animated maps of hourly smoke distribution will be shown as well as comparisons with field observations.