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VIC

VIC is a macroscale hydrologic model that solves full water and energy balances, originally developed by Xu Liang at the University of Washington. VIC is a research model and in its various forms it has been applied to regional watersheds and globally.

You can download the PDF version here

Model architecture

Model description

Main processes being represented

The VIC model (Liang et al., 1994) is a large-scale, semi-distributed hydrologic model. As such, it shares several basic features with the other land surface models (LSMs) that are commonly coupled to global circulation models (GCMs):

The land surface is modelled as a grid of large (>1km), flat, uniform cells ◦Sub-grid heterogeneity (e.g. elevation, land cover) is handled via statistical distributions
Inputs are time series of daily or sub-daily meteorological drivers (e.g. precipitation, air temperature, wind speed)
Land-atmosphere fluxes, and the water and energy balances at the land surface, are simulated at a daily or sub-daily time step
Water can only enter a grid cell via the atmosphere
An offline routing model (Lohmann et al., 1996) is used to simulate the horizontal water fluxes (water transport from the upstream parts of river basins to the basin outlet)

Process represented : water and energy balances

Space : 0.5° x 0.5°

Time : daily or sub-daily

Description of the inputs

Input Type	Variable identification and metric	Temporal and spatial scale	Default source of data in past	Source of data for future scenarios
Climate	Minimum set: Precipitation Maximum air temperature Minimum air temperature Wind speed Facultative variables: Convective rainfall Convective snowfall Large-scale rainfall Large-scale snowfall Incoming long wave radiation Incoming shortwave radiation Specific humidity Relative humidity Surface albedo Atmospheric density Atmospheric pressure Cloud cover Vapour pressure Zonal component of wind speed Meridional component of wind speed Incoming channel flow (total volume over the time step)	0.5° x 0.5°, daily	WATCH forcing data (Weedon et al., 2011)	bias-corrected GCM data (Hagemann et al., 2011)
Land cover	Vegetation class identification number Root zone thickness Leaf Area Index	0.5° x 0.5°	University of Maryland landcover dataset (Hansen et al., 2000)	idem
Soil	Number of moisture layers used by the model Number of thermal solution nodes in the soil column Variable infiltration curve parameter Fraction of Dsmax where non-linear baseflow begins Maximum velocity of baseflow	0.5° x 0.5°	FAO soil map combined with WISE (World Inventory of Soil emission Potentials) (FAO-WISE) pedon database by Batjes (1995)	idem

Description of the outputs

Land-atmosphere fluxes, and the water and energy balances at the land surface

Saturated Area Fraction
Lake surface area as fraction of grid cell area
Root zone soil moisture
Fractional area of snow cover
Base flow out of the bottom layer
Net evaporation from bare soil
Surface runoff
Average surface albedo
Net heat flux into ground
Net downward shortwave flux
Air temperature
Cloud fraction

Input / output visualization tools

A few generic Splus scripts (which can also be run in R) have been developed to allow the user to quickly plot VIC model output.

The main script compares the default output files (including fluxes, snow, and any other default output fields depending on global parameter settings) from two model runs, with time series plots of the data, time series plots of the differences, and scatter plots. These scripts produce multi-page postscript-format plots.

Condition of access to the model code

Source code of VIC and routing model can be downloaded from the VIC-website.

References

http://www.hydro.washington.edu/Lettenmaier/Models/VIC/

Gao, H., Q. Tang, X. Shi, C. Zhu, T. J. Bohn, F. Su, J. Sheffield, M. Pan, D. P. Lettenmaier, and E. F. Wood, 2010: Water Budget Record from Variable Infiltration Capacity (VIC) Model. In Algorithm Theoretical Basis Document for Terrestrial Water Cycle Data Records (in review).

Lohmann D, NolteHolube R, Raschke E (1996) A large-scale horizontal routing model to be coupled to land surface parametrization schemes. Tellus Series a-Dynamic Meteorology and Oceanography 48:708-721.