Input Specifications

There are 3 required input data sources that must be specified in the configuration file or dictionary. Note that it is possible for a single file to be specified for all three sources, provided that it has all of the required data. For examples of the data see the tests/data directory within the MetSim code.

Input forcings

Specified as forcing in the configuration file. This can either be the path to a NetCDF file, or the path to a directory containing ASCII or binary data (in the VIC4 format). The input forcing data is used to provide the base forcing variables. The required variable data is minimum daily temperature, maximum daily temperature, and daily precipitation.

The variable names can be mapped via the configuration file in the forcing_vars section. For more information about how to set up your configuration file see the Configuration Specifications page.

Domain file

Specified as domain in the configuration file. The domain file provides information about the domain MetSim is to be run over. It is required to be a NetCDF file. The domain requires two variables to be valid.

First, is the mask variable, which provides information about which grid cells are valid to run MetSim on. Values that specify grid cells which should be processed are specified via a positive, finite number (one or greater). Cells which MetSim should ignore can be given as 0 or NaN.

Second, is the elev variable. This provides elevation data used for calculation of solar geometry. It should be specified in meters, and only needs to be given at sites which are marked to be processed via the mask variable.

It is important to ensure that all valid locations in mask have data in elev. Failure to ensure this will result in errors during runtime.

State file

The state file provides information about the history of each of the grid cells to be processed. There are four required variables.

The first two are daily minimum and daily maximum temperatures for the 90 days preceeding the start date specified in the configuration file. They should be specified as t_min and t_max respectively. Similarly precipitation should be given as prec. These variables are used to generate seasonal averages which are used in the calculation of shortwave and longwave radiation.

The final required variable is the initial snow water equivalent (SWE) for each grid cell. It should be named swe in the file.

Output Specifications

Attention

The time coordinate in MetSim’s output is local to the location of each cell! This means that for a single time slice in the NetCDF file all locations along a parallel (same latitude) will have the same solar geometry at that time.

The output variables that are available are dependent on the time step being used. There are two cases:

Daily Output

When time_step is set to 1440 in the configuration file, daily values are generated. The following variables are available for output at a daily time step:

  • t_min : Minimum temperature (also a required input value) (C)
  • t_max : Maximum temperature (also a required input value) (C)
  • prec : Precipitation (also a required input value) (mm/day)
  • swe : Snow water equivalent (mm)
  • vapor_pressure : Vapor pressure (kPa)
  • shortwave : Shortwave radiation (W/m^2)
  • tskc : Cloud cover fraction
  • pet : Potential evapotranpiration (mm/day)

Sub-daily Output

  • temp : Temperature (C)
  • prec : Precipitation (mm/timestep)
  • shortwave : Shortwave radiation (W/m^2)
  • vapor_pressure : Vapor pressure (kPa)
  • air_pressure : Air pressure (kPa)
  • rel_humid : Relative humidity
  • spec_humid : Specific humidity
  • longwave : Longwave radiation (W/m^2)
  • tsck : Cloud cover fraction
  • wind : Wind speed (only if given as an input) (m/s)