WRF-Fire development notes

• Restart done
• Read the topography from a file in an ideal run
• Smoothing the terrain gradients for fire spread Input to the fire model the gradient rather than terrain height.

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.

• Canopy fire

Canopy fire colocated with ground fire is not hard. A separate canopy fire would be harder.

• Output to WRF-Chem

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

• 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.

• 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.

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