The soil parameter file is used by VIC to describe the unique soil properties (in addition to several other variables) for each grid cell in the model domain. There are two general formats for this:
Arc/Info Format - this has one separate Arc/Info-ascii export style file for each soil parameter
Ascii (column) Format - this has one file with a column for each soil parameter
The complete list of parameters, as well as sources of data to estimate them and what ranges of reasonable values would be, are available at the soil parameter description links at the web page for VIC Model Operation: Model Preprocessing. A tutorial on how to build a soil file is also available.
For the LDAS domain (-125 to -67 degrees longitude; 25 to 53 degrees latitude) at 1/8 degree resolution, a useful source of data is at the LDAS Parameters web site. Raw soil texture data for the continental US can be obtained from the Penn State's Earth System Science Center. Certain parameters can be estimated from a soil-texture index (see summary table).
The vegetation parameter file describes the vegetative composition of each grid cell, and uses the same grid cell numbering as the soil file (latitudes and longitudes are not included in the file). This file cross-indexes each vegetation class (from any land-cover classification scheme) to the classes listed in the vegetation library. Details on the format of the vegetation parameter file are given on the web page for VIC Model Operation: Model Preprocessing.
The LDAS project has also produced a set of gridded vegetation data for the LDAS domain, available at their web site. This is based on the 1 km vegetation classification developed at UMD. The raw LDAS vegetation data can be converted to a VIC-style with the program LDAS_2_vegparam.c, which can be downloaded here. The cell numbering in both the final soil file and vegetation parameter files must be identical. A sample vegetation library file (matching the UMD classification) can be downloaded here.
Once a vegetation parameter file is created at one resolution, sometimes it is desirable to aggregate the input file to a coarser resolution (e.g. for preliminary calibration or for using an optimization routine). For the vegetation parameter file format including LAI, the program aggregate_LAI_veg_param.c can be downloaded here.
The database developed for the LDAS VIC long-term simulations includes a complete 53 column VIC soil file (VIC version 4.0 with 3 soil layers) in the file soil_ldas.txt covering the entire LDAS domain. The program create_LDAS_soil.c takes as input the name of this LDAS soil file and a list (2 columns) of the latitudes and longitudes of the 1/8 degree cells of interest. The resulting soil file is complete, with the exception of the following, which are determined during calibration: Ds, Dsmax, Ws, b_infilt, soil_depth (each layer); and the columns for annual average precipitation and temperature, which are generated from the meteorological data. Download database and code here. With an ascii/column type soil file developed as described above, a program, create_LDAS_veg_param.c, has been developed to extract a vegetation parameter file from a vegetation parameter database to match the soil file. Download database and code here.
Last modified: Mon Aug 14 18:36:03 PDT 2000