Firebrand Spotting parameterization module for WRF-Fire

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Joined: Tue Apr 20, 2021 4:56 am

Firebrand Spotting parameterization module for WRF-Fire

Post by frediani » Fri Jun 04, 2021 9:52 pm

I'd like to submit a new module for a Firebrand Spotting parameterization developed for WRF-Fire: ... 10506771.1

The parameterization runs in the atmospheric model inner domain and does not modify model variables (no feedback to WRF or WRF-Fire). It was designed for high-resolution simulations and tested using large-eddy simulation (LES) in the inner nest.

I'd like more information on whether any modifications to the WTF cases are necessary. As is, without fire ignition and without specifying the parameters for firebrand spotting on the namelist, the model results will not be affected. Please let me know how to proceed from here.

Parameterization description:

The Firebrand Spotting parameterization was developed for the WRF-Fire component of the WRF model versions starting at 4.0.1. The parameterization couples to WRF-Fire and uses a Lagrangian particle transport framework to advect firebrands in the innermost nest of the domain. Calculations made by the parameterization do not update model variables.

The code comprises two independent modules, one with the physical processes and another with the necessary MPI wrapping routines that were not yet part of the WRF source code. The motivation to separate the MPI routines in an independent module was to enable them to be used in other model parameterizations through a USE statement without importing the firebrand spotting component. The Firebrand Spotting variables are part of and the subroutine is called from start_em.F and solve_em.F, after all the physics parameterizations and relevant halos are completed.

When fires are active, the parameterization identifies areas at risk of fire spotting by modeling transport and physical processes of individual firebrands. Firebrands are released at multiple heights from gridpoints along the fire front with high fire rate-of-spread and denser fuel loads. Particles are transported with the atmospheric flow, and consumed by combustion. Firebrands may burnout entirely or land, once they descend below a given height threshold. Particles that land before complete burnout are accumulated in a 2-D field during regular intervals.

The likelihood of new fire ignitions due to spotting is computed using the ratio of landed firebrands per gridpoint to the total number of landed particles within the corresponding time interval between model outputs. The ratios are then scaled by a function of fuel load and moisture content at the corresponding gridpoints.

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Re: Firebrand Spotting parameterization module for WRF-Fire

Post by kwerner » Tue Jun 29, 2021 5:17 pm

Thank you for informing us about this and for doing the work to create it! To formally request the code modification, you can open a new pull request (PR) in our WRF GitHub repository. Once you do so, the appropriate developers will be notified and will communicate with you, via GitHub, if they have any questions or suggestions. Make sure your GitHub account is set-up to receive email notifications.

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