VIC Model Inputs
VIC input files may be constructed using various programs and datasets. Below are general descriptions of each input file along with links to its structure and the methods that may be used to build it. For a comprehensive example, including an example of each input file, see the Stehekin Basin file in the Sample Data Sets section of the downloads page.
To run VIC, several sets of input data are necessary:
- Global Parameter File
- user_def.h File
- Meteorological Forcing Files
- Soil Parameter File
- Vegetation Library File
- Vegetation Parameter File
And a few more are optional:
Typically a few key parameters in the Soil Parameter File are calibrated. Some parameters in the a href="#LakeParamFile">Lake/Wetland Parameter File are also calibrated.
Global Parameter File
This is the main input file for VIC. It serves two purposes:
- Points VIC to the locations of the other input files and output files
- Sets simulation options, such as start/end dates and modes of operation
More information on the Global Parameter File.
user_def.h File
While this is not technically an "input" file (it is a header file in the model source code), it is worth mentioning because some simulation options are set in this file.
More information on the user_def.h File.
Meteorological Forcings
VIC can take either daily (Precip, Tmax, Tmin, Windspeed) or sub-daily meteorological data as inputs. VIC has some flexibility in which variables and combinations of variables it can use. The contents and formats of the meteorological data files must be described in the global parameter file.
Here is a List of possible input variables (these can always be found in the file vicNl_def.h).
More information on the Meteorological Forcings File and preparing the file.
Soil Parameter File
The soil parameter file serves three main purposes:
- Define the cell ID number of each grid cell. This ID number is essentially a database key that links a grid cell to its parameters in the various parameter files.
- Define the grid cell soil parameters, as well as geographic information such as grid cell center latitude and longitude.
- Define initial soil moisture conditions, to be used in the absence of an initial state file.
The soil parameters can be supplied to VIC in two alternate formats:
- A single Ascii file, with a separate row for each grid cell, with each field containing a different parameter value.
- A set of Ascii Arc/Info grid files, each one containing a map of the values of a single parameter for all the grid cells in the domain.
More information on the ASCII Soil Parameter File and ASCII Arc/Info Grid Soil Parameter File, and preparing the files.
Vegetation Library File
The vegetation library file defines the different landcover types allowed in the simulation.
More information on the Vegetation Library File and preparing the file.
Vegetation Parameter File
The vegetation parrameter file defines the number of vegetation tiles in each grid cell, along with their areal coverage and landcover type, and a few other parameters associated with the tiles.
More information on the Vegetation Parameter File and preparing the file.
(Optional) Initial State File
VIC can save the hydrologic state from any point in the simulation (usually the final state) to a file for the purpose of re-starting the simulation later (as an initial state file). This is useful for simulations that require lengthy spin-up periods or ensemble methods. The initial state file is not required; if it is not specified, VIC will use a default starting condition, and will take initial soil moisture contents from the values specified in the Soil Parameter File.
More information on the State File Structure. An Initial State File may be prepared simply by running VIC with the necessary state file options in the global parameter file.
(Optional) Elevation Band File
By default, VIC assumes each grid cell is flat. This assumption can lead to inaccuracies in snow pack estimates in mountainous grid cells. For this reason, the option exists to have VIC break each grid cell up into a number of elevation bands (also called snow bands) and simulate them separately. Each band's mean elevation is used to lapse the grid cell average temperature, pressure, and precipitation to a more accurate local estimate.
More information on the Elevation Band File and preparing the file.
(Optional) Lake/Wetland Parameter File
By default, VIC does not simulate lakes or surface ponding. If desired, VIC can simulate lakes (as long as they do not have significant inflows coming from the channel network from outside of the current grid cell, i.e. they are fed by local precipitation and runoff within the grid cell). This behavior can be enabled by setting the LAKES option in the global parameter file to the name of a lake parameter file.
More information on the Lake/Wetland Parameter File and preparing the file.
VIC Administrator Last modified: Mon Aug 24 16:13:20 PDT 2009