VIC Retrospective Land Surface Data Set: 1950-2000


Mean Annual Precipitation


Background

The Variable Infiltration Capacity (VIC) model was used to simulate the global land surface hydrological cycle from 1950-2000. The modeling study was done at a 3-hourly time step and at a spatial resolution of 1/8 degree. Details can be found in the journal article:

Maurer, E.P., A.W. Wood, J.C. Adam, D.P. Lettenmaier, and B. Nijssen, 2002: A long-term hydrologically-based data set of land surface fluxes and states for the conterminous United States, J. Climate 15, 3237-3251.

This web site provides access to the data sets developed as part of this study, including the model forcing data set and the model derived variables.

Citing and Registering To Use The Data

We request that users of this data cite the above article in any reports or publications using it. In addition, for our own records we would appreciate users registering here: Click to Register

Known Data Problems or Bugs

A problem has been identified with the archived values for snow water equivalent (3-hourly, daily, and monthly) in areas of high snow accumulation. This primarily affects the Columbia River basin, though local effects in grid cells at high elevation areas with high precipitation appear in other locations (see map of maximum possible extent of affected cells, areas in white are not affected, areas with higher values are more likely to have problems). This is only a data storage problem, and does not affect any other variables.
UPDATE (September 5, 2002): The monthly snow water equivalent (SWE) and SWE tendency files have been repaired.
UPDATE (September 13, 2002): The 3-hourly and daily snow water equivalent (SWE) files have been repaired.

In the ldas_soil_properties.nc file, the depths, porosities, and wilting points for some cells (less than 5% of the domain) were in error. As of September 13, 2002, this has been corrected.

Feb 23, 2004: The temperature forcing data from 1998-2000 for the Colorado river basin were found to have been corrupt. Hence, the output for this period and region are not reliable. This is currently being re-run.

Mar 4, 2011: The soil, vegetation, and snowband parameter files used in running VIC have been added to the ftp site. Also, the NLDAS website links have been updated.

Data Sets

Archived Data Format

All data are archived in netCDF format. The NetCDF home page provides information regarding the data format and links to software that can be used to read and write netCDF files. The data are stored using the compression technique "compression by gathering," which is widely used in land surface implementations of netCDF. More details on compression by gathering are available at this link. A sample script to plot data, using NCO utilities and GMT, from one of these files can be seen here.

Note Related to Soil Moisture Data

Unlike many global and continental data sets, such as the NCEP/NCAR reanalysis, which assume constant soil porosity and depth throughout the domain, this data set has varying soil properties. As discussed in the above reference, the soil porosity for each VIC grid cell is determined based on local soil texture, and soil depths are derived during the calibration process. Therefore, when interpreting volumetric soil moisture (soil wetness) data from this data set, it must be scaled to reproduce relative wetness. One option for scaling the soil moisture is to add all of the pore space in the column (depth times porosity for all three layers), and divide the total volumetric soil moisture by this value. To then use this for initializing the land surface of a model with a 2-meter deep soil column with a porosity of 0.47, for example, this value would be multiplied by 940 (2 x 0.47 x 1000) to obtain an equivalent soil moisture in mm. For the monthly data, the fractional soil moisture, scaled as mentioned here, is available.

Model Forcing and Derived Data

Time Step

Three-Hourly

Daily Summary

Monthly Summary

Related Data Sets

Data Set

Download

Soil Depths and porosities (storage capacities) of 3 soil layers

VIC 4.0.3-formatted calibrated soil files at 1/8th for study domain by basin

VIC 4.0.3-formatted snowband files by basin

VIC 4.0.3-formatted vegetation parameter files by basin with vegetation library

Links to Other Sites with Related Data

Data Set

Link to Page

Mean Elevation of each Grid Cell

Soil Hydraulic Properties

Land Use Classification



Ed Maurer

Last modified: Friday March 4, 2011