SFIRE variables

Back to the WRF-SFIRE user guide.

Introduction

The fire mesh is 2D. Every atmosphere cell is divided into sr_x by sr_y fire cells. The submesh ratios sr_x and sr_y are specified in the file namelist.input. These values are not stored in the NetCDF files, but can be computed from the dimension sizes.

sr_x=west_east_subgrid/west_east_stag = west_east_subgrid/(west_east + 1)
sr_y=south_north_subgrid/south_north_stag = south_north_subgrid/(south_north + 1)

For historical reasons, the fire grid dimensions in the output files are larger than what is actually used by the code internally. The extra space is at the end of the variables of size sr_x in x and sr_y in y. The following is an example of python code for correctly reading FGRNHFX from the file wrfout.

from netCDF4 import Dataset
f=Dataset('wrfout','r')
sr_x=len(f.dimensions['west_east_subgrid'])/(len(f.dimensions['west_east'])+1)
sr_y=len(f.dimensions['south_north_subgrid'])/(len(f.dimensions['south_north'])+1)
fgrnhfx=f.variables['FGRNHFX']
fgrnhfx=fgrnhfx[...,:-sr_y,:-sr_x]

Variables on the fire mesh are located at the centers of the fire mesh cells of a 2D fire mesh.

List of variables

The authoritative information can be always found in the Registry.

State

FXLONG and FXLAT

The position of the centers of fire is stored in the arrays .

Fire variables important for visualization:

• FGRNHFX - heat flux from the ground fire. Higher value means a more intense fire, so it should be brighter.
• FUEL_FRAC - the fuel fraction remaning. 1 means no fire yet, so one can display the original ground colors. 0 or small means burned, so the ground can have a different color, e.g. it could be blackened.
• FIRE_AREA - the proportion of the cell area that is on fire. 0 means no fire yet, 1 means all cell is on fire. It can be also used for ground colors.

See the WRF-Fire user's guide for the description of all fire model variables.