WRF-Fire development notes

Short-term

These are tasks where what to do it is already known, all that remains is to find the time to do it.

• Read the topography from a file in an ideal run
• Input to the fire model the gradient rather than terrain height. See discussion.

This will allow the gradient to be smoothly interpolated in preprocessing in the WPS or in setting up ideal cases. No artificial terrain smoothing is needed. The current scheme interpolates terrain height linearly, and if the mesh the terrain is interpolated from is much coarser than the fire mesh, this results in gradient jumps along the terrain mesh lines. Then, the fire spread rate jumps along the terrain mesh lines.

• Better quadrature for fuel left

The current scheme is second order accurate when all 4 corners of a fire mesh cell are on fire, and exact when all 4 corners are not on fire. In the case when only some of the 4 corners are on fire, the only requirement is that the transition is continuous; the scheme may not be very accurate. This affects the amount of heat output in from a cell in the timesteps when the fireline crosses the cell.

• A standalone driver for the fire code that is independent of WRF.

This is how WRF-Fire was originally developed and such driver was available until late 2008 or so. But, then it fell into disuse and the Fire has grown into the WRF over time.

Long-term

These are more complex tasks or research project, where the method of attack may not be completely clear yet.

• Gradual ignition from a point or a line, without limitation on the initial radius.

The current scheme requires that the ignition area is several fire mesh steps large. When such area ignites all at once, all the heat is output to the atmosphere at once, instead of being output gradually and allowing ground layer circulation to develop over time.

• Canopy fire

Canopy fire colocated with ground fire is easy. A separate canopy fire would be harder.

• Output to WRF-Chem

Output of the combustion products into WRF is also needed to visualize smoke.

Done

• Restart done

• Walking line ignition (as the fireman walks igniting the fire) done
• Remove (by default) the warm perturbation (bubble) from atmospheric initializations in idealized cases done
• Modify the code and add namelist variables allowing for ingesting the cold/warm perturbation of a specified size (for people interested in fire propagation in downburst/convective environments) done