DOI: 10.5061/dryad.63xsj3vdb
title: Data for the western United States large forest-fire stochastic simulator (WULFFSS) 1.0: A monthly gridded forest-fire model using interpretable statistics

description: This archive contains the data and code used to produce the Western United
 States Large Forest-Fire Stochastic Simulator (WULFFSS), version 1.0,
 which is a monthly gridded forest-fire model using interpretable
 statistics. The WULFFSS operates at 12-km resolution and calculates
 monthly probabilities of forest fires ≥100 ha as well as the area burned
 per fire. The model is forced by variables related to vegetation,
 topographic, anthropogenic, and climate factors, organized into three
 indices representing spatial, annual-cycle, and lower frequency temporal
 domains. These indices can interact, so variables promoting fire in one
 domain amplify fire-promoting effects in another. The fire probability and
 size modules use multiple logistic and linear regression, respectively,
 and can be easily updated as new data or ideas emerge. During its training
 period of 1985–2024, WULFFSS captures &gt;70% and &gt;80% of
 observed interannual variability in western US forest-fire frequency and
 area, respectively. It reproduces regional differences in seasonal timing,
 frequencies, and sizes of fires, and performs well in cross-validation
 exercises that test the model’s accuracy in years or regions not
 considered during model training. While lacking fine-scale fire dynamics,
 the model's use of classic statistics promotes interpretability and
 efficient ensemble generation. An important feature of the WULFFSS is that
 it was designed to run within a vegetation ecosystem model, allowing for
 simulations of bidirectional feedbacks between vegetation and fire such
 that simulations can be used to assess how ecosystem changes have altered
 or will alter fire-climate relationships across the western US. The
 model's predictive power should improve with increasingly accurate
 and extensive observational data, and its approach can be extended to
 other regions.
description: # Data for the western United States large forest-fire stochastic
 simulator (WULFFSS) 1.0: A monthly gridded forest-fire model using
 interpretable statistics Dataset DOI:
 [10.5061/dryad.63xsj3vdb](10.5061/dryad.63xsj3vdb) ## Description of the
 data and file structure This repository contains the data and code used to
 produce version 1.0 of the Western United States Large Forest-Fire
 Stochastic Simulator (WULFFSS), as well as the equations that comprise the
 model and code to run the model. The WULFFSS simulates the probabilities
 and sizes of forest fires at least 1 km2 in size every month across
 forested areas of the western US on a 12-km resolution grid. The model is
 forced by variables related to vegetation, topographic, anthropogenic, and
 climate factors, organized into three indices representing spatial,
 annual-cycle, and lower frequency temporal domains. These indices can
 interact, so variables promoting fire in one domain amplify fire-promoting
 effects in another. Fire probability and size models use multiple logistic
 and linear regression, respectively, and can be easily updated as new data
 or ideas emerge. ### Files and variables #### File: code.zip
 **Description:** This is the MATLAB code used to produce the datasets, fit
 the model, and perform simulations. Each file is described here:
 01_make_observed_forest_fire_list.m: Use the WUMI2024a wildfire dataset to
 make a record of western US forest fires that burned ≥1 km2 of forested
 area during the 1985–2024 model calibration period, as well as 1-km
 resolution maps of monthly forest area burned.
 02_make_fire_predictand_datasets.m: Make the forest-fire occurrence and
 fire size records that will serve as the variables that are predicted by
 the fire model. 03_make_12km_maps_of_pyrome_group.m: Make a 12-km
 resolution map of western US pyrome regions.
 04_make_spatial_seasonal_and_temporal_predictor_datasts.m: Make the
 monthly gridded 12-km resolution datasets of potential spatial, seasonal,
 and temporal predictor datasets that will be used in fitting the fire
 model. 05_FitFireModel_Probability.m: Fit the fire probability model and
 write out model equations. 06_FitFireModel_BurnedArea.m: Fit the fire size
 model and write out model equations. 07_PerformSimulations.m: Perform an
 ensemble of simulations and write out outputs.
 08_list_years_to_withhold_in_temporal_cross_validation.m: Determine which
 years to withhold in each fold of the temporal cross-validation exercise.
 09_map_regions_to_withhold_in_temporal_cross_validation.m: Determine the
 regions to withhold in each fold of the spatial cross-validation exercise.
 10_FitFireModel_Probability_CrossValidation_temporal.m: Fit alternative
 fire probability models for the temporal cross validation, each time
 withholding a different sequence of consecutive years from the model
 training. 11_FitFireModel_FireSize_CrossValidation_temporal.m: Fit
 alternative fire size models for the temporal cross validation, each time
 withholding a different sequence of consecutive years from the model
 training. 12_PerformSimulations_CrossValidated_temporal.m: Perform
 simulations using the temporal cross-validation models.
 13_FitFireModel_Probability_CrossValidation_spatial.m: Fit alternative
 fire probability models for the temporal cross validation, each time
 withholding a different region from the model training.
 14_FitFireModel_FireSize_CrossValidation_spatial.m: Fit alternative fire
 size models for the temporal cross validation, each time withholding a
 different region from the model training.
 15_PerformSimulations_CrossValidated_spatial.m: Perform simulations using
 the spatial cross-validation models. get_spi_params.m: function to
 calculate the distribution parameters used in calculating the standardized
 precipitation index (SPI) figures/: This sub-directory contains the code
 used to produce the figures used in the publication that describes the
 WULFFSS model. #### File: firedata.zip **Description:** This directory
 contains the 12-km grids of monthly burned area and fire frequency, as
 well as a list of forest-fire locations and sizes used as the target
 variables when fitting the WULFFSS. This directory also contains a 12-km
 map of the western US forested study region and a 12-km map of pyrome
 groups used to generate uncertainty datasets for the fire probability
 model. #### File: main_model_equations.zip **Description:** This directory
 contains text files with with WULFFSS model’s equations and parameters,
 produced during the model-fitting process. #### File: outputs.zip
 **Description:** This directory contains three sub-directories:
 fire_frequency/: This subdirectory contains netCDFs of fire probability
 estimates produced by each of the six major steps of the process of
 building the fire-probability model. The ProbNFires.nc file is a set of
 monthly 12-km maps of, given the case of ≥1 simulated fire in a given grid
 month, the modeled probability that the number of fires is 2 or 3.
 fire_size/: This subdirectory contains netCDFs of normalized fire size
 anomaly estimates produced by each of the six major steps of the process
 of building the fire-size model. Hindcast/: This subdirectory contains a
 subdirectory for each ensemble of historical WULFFSS simulations that have
 been run. For each ensemble member, there is a text file listing the
 dates, locations, and sizes of each simulated forest fire. For each
 ensemble, there is also a netCDF of 12-km monthly simulated fire
 frequencies (nfires.nc) and forest area burned (burnarea.nc) simulated by
 each ensemble member. #### File: predictors.zip **Description:** This
 directory contains the potential predictor datasets used to fit the fire
 probability and size models, as well as lists of the predictors selected
 by each model, the equations used to transform those predictor variables,
 and .nc files of the transformed predictor variables:
 space_predictor_names.txt: Names of potential spatial predictor variables.
 space_predictor_zscore_equation.txt: Equations to convert spatial
 predictors to z-scores seas_predictor_names.txt: Names of potential
 annual-cycle predictor variables. seas_predictor_zscore_equation.txt:
 Equations to convert annual-cycle predictors to z-scores
 temporal_predictor_names.txt: Names of potential temporal predictor
 variables. temporal_predictor_zscore_equation.txt: Equations to convert
 temporal predictors to z-scores firesize_weightings.txt: For each unique
 forest area burned (1st column), the weighting (0-1, 2nd column) used in
 weighted regressions of the fire-size model. netcdfs/: This subdirectory
 contains the predictor datasets as well as some information used in the
 calculation of standardized datasets: yr_predictors.txt: List of years
 represented by all predictor variables
 veg_model_min_thresholds_for_log10.txt: For biomass-related variables that
 are log-transformed, the minimum allowable values before
 log-transformation fueltotal.nc: netcdf of monthly aboveground live stem
 and branch biomass, used in determining 12-km gridded study domain.
 space/: This subdirectory contains a netCDF of 12-km monthly gridded data
 for each potential spatial predictor. seas/: This subdirectory contains a
 netCDF of 12-km monthly gridded data for each potential annual-cycle
 predictor. temporal/: This subdirectory contains a netCDF of 12-km monthly
 gridded data for each potential temporal predictor. 1km/: This
 subdirectory contains a 1-km netCDF of annual grids of fractional cover by
 a number of landcover types, as well as annual grids of aboveground live
 stem and branch biomass. fire_frequency: This subdirectory contains a
 number of sub-directories with files output while building the
 fire-probability model and called on during simulations: space/: This
 subdirectory contains a MATLAB .mat data file storing model information
 about spatial predictors written out while building the fire-probability
 model, but not needed to perform simulations. There are also two
 sub-directories: transformation_equations/: This sub-directory contains
 text files written out while building the spatial portion fire-probability
 model, most of which are used during simulations. transformed_netcdfs/:
 This sub-directory contains the transformed spatial predictor variables
 for the fire-probability model. seas/: This subdirectory contains a MATLAB
 .mat data file storing model information about annual-cycle predictors
 written out while building the fire-probability model, but not needed to
 perform simulations. There are also two sub-directories:
 transformation_equations/: This sub-directory contains text files written
 out while building the annual-cycle portion of the fire-probability model,
 most of which are used during simulations. transformed_netcdfs/: This
 sub-directory contains the transformed annual-cycle predictor variables
 for the fire-probability model. temporal/: This subdirectory contains a
 MATLAB .mat data file storing model information about temporal predictors
 written out while building the fire-probability model, but not needed to
 perform simulations. There are also two sub-directories:
 transformation_equations/: This sub-directory contains text files written
 out while building the temporal portion of the fire-probability model,
 most of which are used during simulations. transformed_netcdfs/: This
 sub-directory contains the transformed temporal predictor variables for
 the fire-probability model. interactions/: This subdirectory contains a
 MATLAB .mat data file storing model information about the predictors
 representing interactions between the spatial, seasonal-cycle, and
 temporal parts of the fire-probability model, written out while building
 the model but not needed to perform simulations. There are also two
 sub-directories: equations/: This sub-directory contains text files
 written out while building the interactions portions of the
 fire-probability model, most of which are used during simulations.
 netcdfs/: This sub-directory contains the interaction predictor variables
 for the fire-probability model. fire_size: This subdirectory contains a
 number of sub-directories with files output while building the fire-size
 model and called on during simulations: space/: This subdirectory contains
 a MATLAB .mat data file storing model information about spatial predictors
 written out while building the fire-size model, but not needed to perform
 simulations. There are also two sub-directories:
 transformation_equations/: This sub-directory contains text files written
 out while building the spatial portion fire-size model, most of which are
 used during simulations. transformed_netcdfs/: This sub-directory contains
 the transformed spatial predictor variables for the fire-size model.
 seas/: This subdirectory contains a MATLAB .mat data file storing model
 information about annual-cycle predictors written out while building the
 fire-size model, but not needed to perform simulations. There are also two
 sub-directories: transformation_equations/: This sub-directory contains
 text files written out while building the annual-cycle portion of the
 fire-size model, most of which are used during simulations.
 transformed_netcdfs/: This sub-directory contains the transformed
 annual-cycle predictor variables for the fire-size model. temporal/: This
 subdirectory contains MATLAB .mat data files storing model information
 about temporal predictors written out while building the fire-size model
 process, but not needed to perform simulations. There are also two
 sub-directories: transformation_equations/: This sub-directory contains
 text files written out while building the temporal portion of the
 fire-size model, most of which are used during simulations.
 transformed_netcdfs/: This sub-directory contains the transformed temporal
 predictor variables for the fire-size model. interactions/: This
 subdirectory contains a MATLAB .mat data file storing model information
 about the predictors representing interactions between the spatial,
 seasonal-cycle, and temporal parts of the fire-size model, written out
 during the model-building process but not needed to perform simulations.
 There are also two sub-directories: equations/: This sub-directory
 contains text files written out while building the interactions portions
 of the fire-size model, most of which are used during simulations.
 netcdfs/: This sub-directory contains the interaction predictor variables
 for the fire-size model. #### File: cross_validated_spatial.zip
 **Description:** This directory contains a subdirectory for each of the 13
 alternative spatially cross-validated fire models, where each model's
 training dataset was missing data from one of 13 unique regions of the
 western US. For each of the 13 fire models, the subdirectories within
 (firedata/, main_model_equations/, outputs/, and predictors/) are
 structured the same as the similarly named directories associated with the
 main fire model. The netcdf called space_to_withhold.nc is a netcdf
 containing 13 gridded maps of the western US with 12-km grid spacing, each
 indicating the region withheld from the corresponding spatially
 cross-validated model. #### File: cross_validated_temporal.zip
 **Description:** This directory contains a subdirectory for each of the 13
 alternative temporally cross-validated fire models, where each
 model's training dataset was missing data from one of 13 unique
 periods of 3–4 consecutive years. For each of the 13 fire models, the
 subdirectories within (firedata/, main_model_equations/, outputs/, and
 predictors/) are structured the same as the similarly named directories
 associated with the main fire model. The .mat data file called
 yearstowithhold.mat contains 13 cells, each listing the 3-4 year period
 withheld from its corresponding temporally cross-validated model. ####
 File: data.zip **Description:** This directory contains data used to
 produce the predictor and model target data, each in a subdirectory.
 Sub-directories are: climate/: 12-km resolution monthly climate datasets
 used to produce model predictors colormaps/: Text files with colormaps
 used to produce the figures in the figures/ directory. house_density:
 12-km resolution maps of census-based housing density in 1990, 2000, 2010,
 and 2020 and 12-km resolution maps of distance to the nearest location
 exceeding a given population density landcover: 1-km and 12-km resolution
 maps of the various landcover variables used to determine the western US
 forested region and produce model predictor variables related to landcover
 projection/: Geotiff file from MTBS that contains the equal-area map
 projection information used to produce the datasets used. road_distance/:
 12-km maps of distance to nearest road. study_region/: 1-km and 12-km
 resolution maps of the western US study region. Topography/: 12-km
 resolution maps of mean elevation, slope, and standard deviation of 1-km
 mean elevation values within each 12-km grid cell. wildfire/: This
 subdirectory contains observed wildfire data from the WUMI2024a, which can
 be accessed from
 [https://datadryad.org/submission/10.5061/dryad.63xsj3vd4](https://datadryad.org/submission/10.5061/dryad.63xsj3vd4), as well as data on Federal suppression costs and US inflation used for a figure. Contents of this sub-directory are: WUMI2024a_wildfires_1984_2024_no_subfires.txt: The WUMI2024a list of western US wildfire events with no sub-fires. In cases of a parent fire composed of sub-fires (e.g., a fire complex), only the parent fire is listed. WUMI2024a_wildfires_1984_2024_with_subfires.txt: The WUMI2024a list of western US wildfire events with sub-fires. In cases of a parent fire composed of sub-fires (e.g., a fire complex), the sub-fires are listed instead of the parent. WUMI2024a_wildfires_1985_2024_no_subfires_with_forest_fire_area.txt: The WUMI2024a list of western US wildfire events during 1985–2024, with 3 columns appended to the end with each fire’s total forest area burned as well as coordinates of the location of the nearest burned forest area to the fire’s reported ignition location. WUMI2024a_forest_fire_events_1985_2024_with_subfires.txt: List of fire events, including sub-fires, that burned at least 1 km2 forest area during 1985–2024. FederalSuppressionCosts.txt: Annual federal fire-suppression expenditures (USD) for 1985–2023 from [https://www.nifc.gov/fire-information/statistics/suppression-costs](https://www.nifc.gov/fire-information/statistics/suppression-costs). US_Inflation.txt: Monthly inflation rate of US Dollars 1km_maps/: This subdirectory contains annual zip files containing, for each fire in the WUMI2024a from 1985–2024, a netCDF 1-km resolution map of fractional area burned and a shapefile of the fire perimeter. This subdirectory also contains a netCDF called burnarea.nc that is a set of monthly 1-km resolution maps of areas burned for 1984–2024 from the WUMI2024a. subfires/: This subdirectory contains a text file for each parent fire in the WUMI2024a that is composed of multiple sub-fires. Each parent fire is listed in the top row, and each sub-fire is listed below, separated by a blank row. #### ## Code/software The model was produced using MATLAB 2024a, as was the code provided in this repository. ## Access information Data was derived from the following sources: * Observed fire data from the Western US MTBS-Interagency database of large wildfires (WUMI2024a), available from [https://datadryad.org/submission/10.5061/dryad.63xsj3vd4](https://datadryad.org/submission/10.5061/dryad.63xsj3vd4) * Climate data from: * [https://www.ncei.noaa.gov/products/land-based-station/nclimgrid-daily](https://www.ncei.noaa.gov/products/land-based-station/nclimgrid-daily) * [https://prism.oregonstate.edu/](https://prism.oregonstate.edu/) * [https://wrf-cmip6-noversioning.s3.amazonaws.com/index.html#downscaled_products/reanalysis/era5/](https://wrf-cmip6-noversioning.s3.amazonaws.com/index.html#downscaled_products/reanalysis/era5/) * [https://psl.noaa.gov/data/gridded/data.narr.html](https://psl.noaa.gov/data/gridded/data.narr.html) * Topography from [https://www.ngdc.noaa.gov/mgg/topo/globe.html](https://www.ngdc.noaa.gov/mgg/topo/globe.html) * Annual USGS National Landcover Database: [https://www.usgs.gov/centers/eros/science/annual-national-land-cover-database](https://www.usgs.gov/centers/eros/science/annual-national-land-cover-database) * Housing unit density: [https://silvis.forest.wisc.edu/data/wui-change/](https://silvis.forest.wisc.edu/data/wui-change/) * Global roads data: [https://search.earthdata.nasa.gov/search/granules?p=C1000000202-SEDAC](https://search.earthdata.nasa.gov/search/granules?p=C1000000202-SEDAC)