How to diagnose fuel properties in WRF-SFIRE

Back to the WRF-SFIRE user guide.

The fuel properties in WRF-Fire are given in file namelist.fire. These serve to create coefficients in the Rothermel's formula. To aid diagnostics it is useful to graph the resulting fire spread rate as a function of wind and slope. The graphs are available in metric units, as well as in English units for direct comparison with the published spread rate graphs for the Scott-Burgan fuel categories.

Prerequisites

Location of the codes

The fuel properties of every category of the fuel are defined in file namelist.fire, which needs to be in the current directory.
The fire rate of spread computation is done in file module_fr_sfire_phys.F, split between two subroutines. First, the coefficients at every point are precomputed from fuel properties in subroutine set_fire_params at initialization. In every time step, the spread rate at a point is then computed from those coefficients in subroutine fire_ros.
The computation has been duplicated in Matlab for diagnostic purposes in file fire_ros.m
The plot routine to create graphs like shown here is plot_fuel.m

Heat flux diagnostics

plot_fuel also computes and prints several diagnostic quantities derived from fuel properties, including total heat density generated by the combustion of the fuel over time (J/m²), and the maximal heat flux density (W/m²) from the initial slope of the fuel loss curve. These can be compared with the statistic printed by WRF-Fire while running (maximal heat flux density, total heat flux of the fire, total heat generated by the fire).

Step-by-step instructions

Run WRF-Fire, you can kill it right after the the first time step. There will be file fuels.m created in the current directory.
Start Matlab in the directory test/em_fire to set up the search path properly.
In Matlab, navigate to the directory with the fuels.m file
Type fuels. This will create variable fuel. Say you want to check fuel 3. Type fuel(3) to see what is there.
Type plot_fuel(fuel(3)) to create the graph below in metric units, and plot_fuel(fuel(3),'sb') for the same units as in Scott and Burgan (2005). Type help plot_fuel for further information. Note: The graph data were created in WRF-Fire and stored in the fuel variable.
Type edit fire_ros to see the fire spread rate calculation recreated in Matlab.
Type big(check_ros(fuel)) to make sure the calculation in Matlab is the same as in WRF-Fire, it should return rounding error only (less than 1e-4)

Diagnostics provided

The plot_fuel command displays the graph of rate of spread as a function of wind speed, slope, and fuel moisture.

Works with

Version 16 Sep 2010
Version 29 Aug 2012 and hopefully later
Matlab R2010a, 2012a, and hopefully later

References

Anderson, H. E., 1982. Aids to determining fuel models for estimating fire behavior. U.S. Forest Service General Technical Report INT-122. Ogden, UT. pdf (The original 13 fuel models)
Baughman, R. G. and F. A. Albini.,1980. Estimating midflame windspeeds. In Sixth Conference on Fire and Forest Meteorology, Seattle, WA (Society of American Foresters) pdf (Windspeed reduction from 20ft)
Rothermel, R.C., 1972. A mathematical model for predicting fire spread in wildland fuels. Res. Pap. INT-115. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 40 pp. pdf (The original for reference)
Rothermel, R. C., 1983. How to predict the spread and intensity of forest and range fires. U.S. Forest Service General Technical Report INT-143. Ogden, UT. pdf (Updated version)
Scott, J. H. and Burgan, R. E., 2005. Standard fire behavior fuel models: a comprehensive set for use with Rothermel's surface fire spread model. Gen. Tech. Rep. RMRS-GTR-153. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 72 pp. pdf (More detailed fuel models, with rate of spread curves)

External links