# Running the Land Surface Model (wsim_lsm)¶

The wsim.lsm utility runs one or more iterations of the WSIM Land Surface Model.

Usage is as follows:

wsim_lsm --state <file> \
[--forcing <file>]... \
--flowdir <file> \
--wc <file> \
--elevation <file> \
--results <file> \
--next_state <file> \
[--loop n]

• --state is a netCDF file representing the input state of the model. It must provide four variables:

• Dr amount of detained runoff in millimeters

• Ds amount of detained snowmelt in millimeters

• Snowpack snowpack water equivalent in millimeters

• Ws soil moisture in millimeters

• snowmelt_month the number of consecutive months of melting conditions

In addition, the state file must define a global attribute yearmon that specifies a year and month YYYYMM format. The state file will be considered to represent conditions at the start of this month.

• --forcing specifies one or more netCDF files of forcing data to be used, with each file providing data for a single model iteration. Multiple --forcing arguments may be provided, and each argument may refer to a single file or a glob of multiple files. Forcing data will be applied in a character-sort order based on the file names of the inputs, not the order in which they are specified. Each forcing file must contain the following variables:

• T the average monthly temperature in degrees Celsius

• Pr the total monthly precipitation (rainfall and snowfall) in millimeters

• pWetDays the fraction of days during which precipitation falls

• --wc a file providing the soil moisture holding capacity in millimeters

• --elevation a file providing land surface elevation in meters

• --flowdir a file providing a surface flow direction matrix (as described in Flow Direction Specification)

The following arguments define model outputs:

• --results a netCDF file to which model results will be written. If the filename contains the pattern %T, results from all model iteration will be written to disk as separate files, with the filename formed by substituting the timestep year-month for %T. If the %T pattern is not present in the filename, only the results of the final iteration will be written to disk.

• --next_state a netCDF file to which a model state will be written, suitable for use in a subsequent model iteration. Substitution of %T is performed in the same manner as for the --results argument.

• --loop will cause the input forcing data to be cycled multiple times. This is useful during model spin-up.