The following parameters are found in r/run_stilt.r and are used to configure STILT. These settings are used to adjust model parameters, execute parallelized simulations, and calculate produce upstream influence footprints.

System configuration

Arg Description
project Project name
stilt_wd Working directory for the given project
lib.loc Path to R package installations, passed to library()

Parallel simulation settings

Arg Description
n_nodes If using SLURM for job submission, number of nodes to utilize
n_cores Number of cores per node to parallelize simulations by receptor locations and times
slurm Logical indicating the use of rSLURM to submit job(s). When using SLURM, a _rslurm directory is created at the top level of the STILT project. This directory contains the SLURM submission scripts and node-specific log files.
slurm_options Named list of options passed to sbatch using rslurm::slurm_apply(), which typically includes time, account, and partition values

Simulation timing

Arg Description
t_start/t_end Receptor time(s) to initialize simulations, formatted as 'yyyy-mm-dd HH:MM:SS' UTC
run_times Hourly simulations spanning t_start through t_end of length n

Receptor locations

Arg Description
lati Receptor latitude(s), in degrees. Can be a single value or a vector of length n
long Receptor longitude(s), in degrees. Can be a single value or a vector of length n
zagl Receptor height(s), in meters above ground level. Can be a single value or a vector of length n

Simulation timing and receptor locations are defined in this way for convenience and then expanded to contain the unique receptors in a x, y, z, t table. For more complex lists of receptors, this table can be created manually instead of using the simulation timing and receptor location definitions. To specify the receptors manually, a data frame named receptors can be created with column names run_time (POSIXct), long (double), lati (double), and zagl (double).

'data.frame': 100 obs. of 4 variables:
$ run_time: POSIXct, format: "2015-07-02 11:00:00" "2015-07-02 11:00:00" ...
$ long : num -112 -112 -112 -112 -112 ...
$ lati : num 40.8 40.8 40.8 40.8 40.8 ...
$ zagl : num 5 5 5 5 5 5 5 5 5 5 ...

Meteorological data input

Arg Description
met_directory Full directory path in which ARL compatible meteorological data files can be found
met_file_format String detailing file naming convention for meteorological data files using a mixture of datetime and regex syntax. The formatting string accepts grep compatible regular expressions (‘.*.arl’), strftime compatible datetime strings (‘%Y%m%d%H’) or any combination of the two (‘d.*_%Y%m%d_filename.arl’). Datetime syntax is expanded to all unique combinations required for the receptor and simulation duration and the intersection between the requested files and files available in met_directory is determined with grep, allowing partial matching and compatible regular expressions to be used to identify the relevant data. Matching does not require the full format to be specified - e.g. ‘*.arl’, ‘%Y’, ‘%Y%m%d’, ‘%Y%m%d_d0.*.arl’ would all match with a file named ‘20180130_d01.arl’ for a relevant receptor. For timestamped meteorological data files, supplying the structure of the timestamp is sufficient and recommended to avoid unexpected behavior with regular expressions. To require a minimum number of files to be present for a given simulation to proceed, see n_met_min.
n_met_min Minimum number of meteorological data files with which to proceed with simulation. Useful for capturing missing periods. For a -24 hour simulation using the 6 hour HRRR met data files, n_met_min should be set to 5, since find_met_files() ensures that data before and after the simulation is included. Defaults to 1.

NOAA publishes High Resolution Rapid Refresh (HRRR) mesoscale model data in the ARL packed format required for STILT at This is often the easiest place to start but is only available after June 15, 2015. The coupling of the popular Weather Research and Forecasting (WRF) model with STILT is well documented by Nehrkorn, 2010.

Model control

Arg Description
n_hours Number of hours to run each simulation; negative indicates backward in time
numpar number of particles to be run; defaults to 200
rm_dat Logical indicating whether to delete PARTICLE.DAT after each simulation. Default to TRUE to reduce disk space since all of the trajectory information is also stored in STILT_OUTPUT.rds alongside the calculated upstream influence footprint
run_foot Logical indicating whether to produce footprints. If FALSE, run_trajec must be TRUE. This can be useful when calculating trajectories separate from footprints
run_trajec Logical indicating whether to produce new trajectories with hymodelc. If FALSE, will try to load the previous trajectory outputs. This is often useful for regridding purposes
timeout number of seconds to allow hymodelc to complete before sending SIGTERM and moving to the next simulation; defaults to 3600 (1 hour)
varsiwant character vector of 4-letter hymodelc variables. Options include a vector containing a minimum of 'time', 'indx', 'lati', 'long', 'zagl', 'foot' and optionally containing elements from the following options:

Footprint gridding

Arg Description
xmn grid start longitude, in degrees from -180 to 180
xmx grid end longitude, in degrees from -180 to 180
ymn grid start latitude, in degrees from -180 to 180
ymx grid end latitude, in degrees from -180 to 180
xres resolution for longitude grid, in projection units (degrees for lat/lon, meters for other)
yres resolution for latitude grid, in projection units (degrees for lat/lon, meters for other)
hnf_plume logical indicating whether to apply a vertical gaussian plume model to rescale the effective dilution depth for particles in the hyper near-field. This acts to scale up the influence of hyper-local fluxes on the receptor. If enabled, requires varsiwant to include a minimum of dens, tlgr, sigw, foot, mlht, samt. Defaults to TRUE
projection proj4 string defining the map projection of the footprint netCDF output
smooth_factor factor by which to linearly scale footprint smoothing; 0 to disable all smoothing, defaults to 1
time_integrate logical indicating whether to integrate footprint over time or retain discrete hourly time steps in footprint output

Transport and dispersion

Arg Description
conage particle/puff conversions at conage (hours); defaults to 48
cpack binary concentration packing. 0 - all grid points written to file. 1 - only nonzero points written to file. 2 - special non-regular grid. Defaults to 1
delt integration timestep [min]; if set to 0.0, then timestep is dynamically determined
dxf horizontal x grid adjustment factor for ensemble; defaults to 1
dyf horizontal y grid adjustment factor for ensemble; defaults to 1
dzf vertical factor for ensemble; defaults to 0.01 ~ 250m
emisshrs duration of time to release particles over at the start of simulation, in hours; defaults to 0.01
frhmax maximum value for horizontal rounding parameter; defaults to 3
frhs horizontal puff rounding fraction for merge; defaults to 1
frhs mass rounding fraction for enhanced merging; defaults to 0.1
frmr the fraction of the mass that is permitted to be removed at krnd intervals. For certain simulations, such as when a pollutant has a high ambient background relative, a small removal rate will significantly reduce the number of puffs on the grid at no loss in accuracy; defaults to 0
frts temporal puff rounding fraction for merge; defaults to 0.1
frvs vertical puff rounding fraction for merge; defaults to 0.1
hscale horizontal Lagrangian time scale (sec); defaults to 10800
ichem special chemistry or conversion modules. 1 - concentration grid treated as source-receptor matrix format. 2 - convert pollutant from species #1 to species #2. 3 - enable pm10 dust storm emission module. 4 - configure concentration grid similar to meteorology grid. 5 - treat 3D particle deposition using probability function. 7 - enable water surface transport of particle deposition. Defaults to 0
iconvect flag for convection. If set to 1, then runs excessive convection as described in Gerbig et al., 2003. For specialized RAMS output, the particles will be vertically redistributed according to the output convective mass fluxes; defaults to 0
isot flag used to set the isotropic turbulence option; defaults to 0 to compute horizontal turbulence from wind field deformation. Setting to 1 results in the horizontal turbulence to be the same in both the u and v directions
kbls boundary layer stability derived from 1 - heat and momentum fluxes or 2 - wind and temperature profiles. Defaults to 1
kblt boundary layer turbulence parameterization. 1 - Beljaars/Holtslag and Betchov/Yaglom. 2 - Kanthar/Clayson. 3 - TKE field from input meteorology data file. 4 - velocity variances from input meteorology. Defaults to 1
kdef horizontal turbulence computation. 0 - in proportion to vertical turbulence. 1 - computed from velocity deformation. Defaults to 1
khmax max age a particle is allowed to attain; defaults to 9999
kmix0 minimum mixing depth (abs(kmix0) is used as the minimum mixing depth), negative values are used to force mixing heights coincident with model levels; defaults to 250
kmixd PBL height computation: compute from bulk Ri profile (but see zicontroltf); defaults to 3
kmsl starting heights default to AGL = 0 or MSL = 1; defaults to 0
kpuff horizontal puff dispersion. 0 - linear. 1 - square root. Defaults to 0
krnd at this interval in hrs, enhanced puff merging occurs; defaults to 6
kspl standard splitting interval (hours); defaults to 1
kzmix vertical mixing adjustments. 0 - none, vertical diffusivity in PBL varies with height. 1 - vertical diffusivity in PBL single average value. 2 - scale PBL values by tvmix. 3 - scale free-troposphere values by tvmix. Defaults to 1
maxdim maximum number of pollutants to carry on one mass particle; defaults to 1
maxpar maximum number of particles carried in simulation; defaults to 10,000
mgmin determines the size of the sub domain, set >1000 when working with high-res WRF-ARW met fields
ncycl pardump output cycle time; defaults to 0
ndump flag to dump all particle/puff points at the end of a simulation to a file called PARDUMP. This can be read at the start of a new simulation to continue the previous calculation. Valid settings include 0 (no i/o), 1 (read/write), 2 (read only), 3 (write only); defaults to 0
ninit particle initialization. 0 - none. 1 - once. 2 - add. 3 - replace. Defaults to 1
nturb no turbulence flag; defaults to 0, which includes turbulence rather than simulating mean trajectories
outdt interval [min] to output data to PARTICLE.DAT; defaults to 0.0, which outputs at every timestep
outfrac the fraction of the particles that are allowed to leave the model domain (given by met data); defaults to 0.9. If exceeded, the model stops
p10f dust threshold velocity sensitivity factor; defaults to 1
qcycle optional cycling of emissions (hours); defaults to 0
random flag that tells the random number generator whether to have a different random sequence for each model run (0 - false, 1 - true); defaults to 1
splitf horizontal flow splitting. 0 - disable. 1 - automatic size adjustment. >1 - constant value. Defaults to 1
tkerd day (unstable) turbulent kinetic energy ratio; defaults to 0.18
tkern night (stable) turbulent kinetic energy ratio; defaults to 0.18
tlfrac the fraction of the lagrangian timescale TL to set as timestep in dispersion subroutine. The smaller this fraction is, the more finely the turbulence is resolved; defaults to 0.1
tratio maximum fraction of gridcell to be travelled by a particle in a single integration timestep. This determines the timestep if DELT is set to be dynamic
tvmix vertical mixing scale factor; defaults to 1
veght height below which a particle’s time spent is tallied; defaults to 0.5, which specifies half of the PBL. Setting <=1.0 specifies a fraction of the boundary layer height, and setting >1.0 specifies a height above ground in meters
vscale vertical Lagrangian time scale (sec); defaults to 200
w_option vertical motion calculation method. 0: use vertical velocity from data, 1: isob, 2: isen, 3: dens, 4: sigma; defaults to 0
zicontroltf flag that specifies whether to scale the PBL heights in STILT uniformly in the entire model domain; defaults to 0. If set to 1, then STILT looks for a file called “ZICONTROL” that specifies the scaling for the PBL height. The first line indicates the number of hours that the PBL height will be changed, and each subsequent line indicates the scaling factor for that hour
ziscale manually scale the mixed-layer height, with each element specifying a scaling factor for each simulation hour (ziscale can be of length that is smaller than abs(nhrs). A vector can be passed as a list (e.g. ziscale <- list(rep(0.8, 24)) scales the mixed layer height to 80% for the first 24 hours of all simulations) or a list of vectors specific to each simulation (e.g. ziscale <- rep(list(rep(0.8, 24)), nrow(receptors)))
z_top top of model domain, in meters above ground level; defaults to 25000.0

Transport error calculations

Arg Description
siguverr standard deviation of horizontal wind errors [m/s]
tluverr standard deviation of horizontal wind error timescale [min]
zcoruverr vertical correlation lengthscale [m]
horcoruverr horizontal correlation lengthscale [km]
sigzierr standard deviation of mixed layer height errors [%]
tlzierr standard deviation of mixed layer height timescale [min]
horcorzierr horizontal correlation lengthscale of mixed layer height errors [km]