Use of spatially refined satellite remote sensing fire detection data to initialize and evaluate coupled weather-wildfire growth model simulations

Modeling systems that join a full numerical weather prediction model with wildfire behavior components (i.e. coupled weather-wildfire models) have been developed and have shown skill at simulating the unfolding of wildfire events, capturing fire growth, the shape of the fire, and fire phenomena such as fire whirls and dramatic increases in intensity. Large wildfires can cover hundreds of thousands of acres and continue for months, varying in intensity as they encounter different environmental conditions, which may vary dramatically in time and space during a single fire. The duration of such events poses a prediction challenge, as meteorological models lose skill over time after initialization. Moreover, validation data for such models is limited and fire mapping and monitoring has been done piecemeal with infrared imaging sensors producing 12-hourly maps of active fires with nominal 1 km pixels, complemented by sub-hourly observations from geostationary satellites at coarser resolution. Other tools are valuable but not routine; the USDA Forest Service FireMapper airborne infrared mapping radiometer FireMapper has provided unsaturated high-resolution mapping data for wildfires-of-opportunity and, in addition to the USDA Forest Service National Infrared Operations nighttime airborne mapping, has been used as an intelligence resource for high priority wildland fire operations. Most significantly, modeling and monitoring have been done separately, with models simulating fires from their ignition time or first report.

We present results for a wildfire observed in June 2012 in New Mexico using an innovative approach to improving the simulation of large, long-duration wildfires, either for retrospective studies or forecasting in a number of geophysical applications. The approach uses (1) the Coupled Atmosphere-Wildland Fire Environment (CAWFE) Model, a numerical weather prediction model two-way coupled with a module representing the rate of spread of a wildfire's flaming front, its rate of consumption of different wildland fuels, and the feedback of this heat release upon the atmosphere - i.e. 'how a fire creates its own weather', combined with (2) spatially refined (375 m) satellite active fire data derived from the new Visible Infrared Imaging Radiometer Suite (VIIRS) launched in October 2011 aboard the Suomi National Polar-orbiting Partnership, which is used for initialization of a wildfire already in progress in the model and evaluation of its simulated progression at the time of the next pass. Results show that initializing a fire that is 'in progress' with VIIRS data and a weather simulation based on more recent atmospheric analyses can overcome several issues and improve the simulation of late-developing fires and of later periods (particularly those with growth periods separated by lulls) in a long-lived fire.