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)
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 Simulation timing, 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. To specify the receptors manually with this format, a data frame 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 strftime() compatible file naming convention to identify meteorological data files necessary for the timing of the simulation, such as %Y%m%d.%Hz.hrrra. Also accepts wildcards that match regular expression patterns passed to dir(), such as wrfout_d0*_jul.arl
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.

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
delt integration timestep [min]; if set to 0.0, then timestep is dynamically determined
n_hours Number of hours to run each simulation; negative indicates backward in time
numpar number of particles to be run; defaults to 200
outdt interval [min] to output data to PARTICLE.DAT; defaults to 0.0, which outputs at every timestep
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_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 NULL for all variables, or a vector containing a minimum of c('time', 'indx', 'lati', 'long', 'zagl', 'foot') and optionally containing 'sigw', 'tlgr', 'zsfc', 'icdx', 'temp', 'samt', 'shtf', 'tcld', 'dmas', 'dens', 'rhfr', 'sphu', 'solw', 'lcld', 'zloc', 'dswf', 'wout', 'mlht', 'rain', or 'crai'

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 degrees
yres resolution for latitude grid, in degrees
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. Defaults to TRUE
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
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
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
krnd at this interval in hrs, enhanced puff merging occurs; defaults to 6
mgmin determines the size of the sub domain, set >1000 when working with high-res WRF-ARW met fields
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
nturb no turbulence flag; defaults to 0, which includes turbulence rather than simulating mean trajectories
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
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
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
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
w_option vertical motion calculation method. 0: use vertical velocity from data, 1: isob, 2: isen, 3: dens, 4: sigma; defaults to 0
z_top top of model domain, in meters above ground level; defaults to 25000.0
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

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]