To obtain the latest source code for the VIC model, please click here
As of Monday December 8, 2003 the current release is VIC version 4.0.4.
The release announcement is posted below:
December 1, 2003: VIC release 4.0.4
This release covers fixes for a small number of additional bugs discovered
since the release of 4.0.4 beta r3, plus 2 new features.
New Features:
- Typing 'vicNl -v' on the command line now displays the version
of VIC you are running. This provides a fast, simple way of
determining the version of VIC without running a simulation.
- The parameters {Ds, Dsmax, Ws and c} in the soil parameter file
may now be replaced by the set of ARNO baseflow parameters
{d1, d2, d3, d4}. To enable VIC to read the ARNO baseflow
parameters, you must add the following line to the global
parameter file:
ARNO_PARAMS TRUE
and replace {Ds, Dsmax, Ws, and c} with {d1, d2, d3, and d4}
in the soil parameter file.
To disable this behavior, your soil file should contain
{Ds, Dsmax, Ws, and c} and your global parameter file should
contain:
ARNO_PARAMS FALSE
or you may omit the ARNO_PARAMS line entirely.
Modifications:
read_vegparam.c:
Applied Alan Hamlet's fix for COMPUTE_TREELINE option,
which fixed a segmentation fault when COMPUTE_TREELINE=TRUE.
This consisted of removing the call to realloc and
instead allocating an extra veg class to begin with,
as well as assigning this extra veg class a very small
fraction of the grid cell's area to avoid changing the
results for areas below the treeline. TJB
runoff.c:
This fixed strange behavior (spikes) in bottom-layer
soil moisture and baseflow for low liquid moisture
conditions (e.g. frozen soils). Changed calculation
of dt_baseflow to go to zero when soil liquid moisture
<= residual moisture. Changed block that handles case
of total soil moisture < residual moisture to not allow
dt_baseflow to go negative. TJB
write_model_state.c, read_initial_model_state.c:
(bugs found by Lifeng Luo at Princeton)
Read_initial_model_state was not parsing ASCII state
files according to the format written by
write_model_state. Modified write_model_state.c to
add a "\n" after writing mu. Modified
read_initial_model_state to loop over tmp_Nveg and
tmp_Nband when searching for the desired cellnum, and
to read the correct number of lines per veg class
once the desired cellnum has been found. TJB
vicNl_def.h, get_global_param.c, read_soilparam.c:
Added the ARNO_PARAMS option. If TRUE, read_soilparam
reads the ARNO baseflow parameters d1, d2, d3, and d4
and converts them to Ds, Dsmax, Ws, and c. TJB
snow_utility.c:
In the snow_density function, modified the checks on
delta_depth so that the condition is
delta_depth > MAX_CHANGE*depth
Modified compression due to aging to only be calculated
if depth > 0. TJB
global.h, vicNl.c, cmd_proc.c:
Modified the version information banner to display the
version string defined in global.h. Added -v option
to display version information as well. TJB
September 5, 2003: VIC release 4.0.4beta r3
snow_utility.c: modification by KAC
Added check to keep compression from aging from exceeding
the actual depth of the snowpack.
get_global_param.c, initialize_atmos.c, read_vegparam.c,
vicNl_def.h: modification by KAC
Moved COMPUTE_TREELINE flag from user_def.h to the
options structure. Now when not set to FALSE, the
value indicates the default above treeline vegetation
if no usable vegetation types are in the grid cell
(i.e. everything has a canopy). A negative value
will cause the model to use bare soil. Make sure that
positive index value refer to a non-canopied vegetation
type in the vegetation library.
To activate treeline calculation, add the following to
your global control file:
COMPUTE_TREELINE n
If n < 0, the default above treeline vegetation is
set to bare soil. If n >= 0, the default vegetation type
is set to type n in the vegetation library.
To deactivate treeline calculation, add the following or remove
the line from the global control file:
COMPUTE_TREELINE FALSE
WARNING #1: Since the model does not store default root zone
distributions, the default vegetation type will use the
values from the last defined vegetation type for the current
grid cell (i.e. veg type N-1, prior to the addition of the
new vegetation type).
WARNING #2: If you are using GLOBAL_LAI, than the LAI and
dew storage terms for the default vegetation type will be set
to the values used by the last occurrence of the default
vegetation type.
write_model_state.c: bug found by AWW and KAC
Modified to print space before dz_node for ASCII state
file, this corrects a problem with state files created
for models using the Cherkauer and Lettenmaier (1999) heat
flux formulation.
June 4, 2003: VIC release 4.0.4beta r2
This covers bugs found during tests with the snow algorithm.
solve_snow.c: Bug found by KAC
Counter for number of days since last snowfall was
incremented twice in the MELTING update. This has been
fixed.
solve_snow.c: modification by KAC
Added check so that MELTING flag is only TRUE if melt
occurs in the melt season - currently this is defined
between March 1 and October 1. Otherwise the MELTING
flag can trigger rapid very early season melt
write_model_state.c, read_initial_model_state.c, open_state_file.c,
check_state_file.c: Modification by KAC
Modified to handle both ASCII and BINARY state files.
NOTE: ASCII mode is designed to make it easier to create
a state file for initializing a point model. It includes
all features of the Binary state file, but values are
truncated so the resulting restart will not be identical.
If you need an exact restart, use the Binary files. Also
removed ice content from the state file as it is computed
at the beginning of each time step, so storing its value
is unnecessary.
April 23, 2003: VIC release 4.0.4beta r1
This covers bug fixes found by beta testers and fixed in the version of
the code bundled with this file.
surface_fluxes.c: (found by Ingjerd Haddeland)
Indexing fix sent SNOW_STEP to calc_surf_energy_bal rather
than the model time step, meaning that without snow the
evaporation was computed for SNOW_STEP hours rather than a
full day. This was fixed by introducing step_inc to
index the arrays, while step_dt keeps track of the correct
time step.
March 27, 2003: VIC release 4.0.4beta
This release covers patches for several bugs found in 4.0.3, which were
never formally released (i.e. the downloadable source code was modified,
but no major announcement was made). It also includes other fixes and
modifications that have been identified as being needed prior to releasing
version 4.1.0, which will involve several significant changes (including
lakes & wetlands, spatial snow & frost, and a closed canopy energy balance).
Modifications:
Snow albedo update: (found by Keith)
In previous releases, the snow albedo function has been hyper
sensitive to trace amounts of snowfall during the melt period.
Whenever new snow falls or the cold content falls below 0, the
albedo is switched from the ablation curve to the accumulation
curve. This curve is then followed until the cold content
exceeds 0, indicating it is in the spring melt season. This is
fine when accounting for thin early season snowpacks or mid-
season melt events, however, a cold snap or light dusting of
snow should not reset the snowpack albedo to much higher winter
values for days or weeks at a time. This release of the model
monitors the state of pack with the variable MELTING. This
flag keeps the snowpack on the ablation curve unless new snow-
fall exceeds a threshold (TraceSnow in user_def.h) indicating
that the top of the snowpack should be represented by the albedo
of the new snow.
Model initialization: (found by Ulysses and Keith)
In previous releases, the initialization of soil layer moist[]
and ice[] was within a second set of loops for band and
vegetation, using the same counters. Because of the dual use
of counters, initialization was not completed correctly. The
primary effect of this was that thermal node values beyond the
first vegetation type were not correctly initialized, which
caused the model to crash during some simulations with full
energy or frozen soils active. Without frozen soil, most
simulations would compensate for the problem within their
spin-up time, so it is unlikely that this bug impacts any
simulations not employing frozen soil.
Snow time step: (found by Andy, et al.)
The snow algorithm needs to run sub-daily for the energy balance
components to function properly. This means that for daily
simulations, the snow model must be solved at a finer (sub-daily)
time step. In the previous release, initialize_atmos.c stored
sub-daily met data in each days variable using positions (e.g.
0,1,..8 for 3 hour data). In surface_fluxes.c the model indexed
the sub-daily time steps used by the snow algorithm with hours
(e.g. 0,3,6,...21 for three hour data). This means the arrays
were incorrectly indexed and the resulting model simulations
would be wrong. The fix implemented here has been tested under
several model configurations and is deemed the official version.
WARNING: There are several versions of this fix circulating,
please update your code to this version - the previous fixes
may not work in all circumstances!
FROZEN_SOIL active flag: (found by Ed and Justin)
The cause of the problem is a bug in the code that occurs when
the global frozen soils flag (FROZEN_SOILS) is set to true but
the individual cell frozen soil flag (FS_ACTIVE) is set to
false. This causes the change in soil heat storage to be
calculated incorrectly. This was fixed by adding additional
conditions within frozen_soil.c and initialize_model_state.c,
which verify the FS_ACTIVE is TRUE before running
estimate_layer_ice_content. This avoids the problem of the
soil layer ice content being set to a positive value, ignored
by the rest of the model.
Vapor pressure: (Keith)
All internal vapor pressure calculations are now done in
Pascals. Previous release versions, switched between Pa
and kPa, so this simply removes the extra step. The input
file format is unchanged, so there should be no change to
model output (model might run slightly faster, but it is
also unlikely that this will be witnessed by a normal user).
Constant dew despite changing LAI: (Dave Peterson)
The modification of read_vegparam.c to update LAI based on
a grid cell specific value did not change the values of Wdmax.
Wdmax values were computed in read_veglib.c based on the
default LAI values, so they did not necessarily reflect the
actually LAI values used for the grid cell. Values for Wdmax
are now computed in read_vegparam.c whenever GLOBAL_LAI are
provided. The effects of this change will change in magnitude
based on how different the cell LAI values are from those in
the default library file.
DRY_TIME error: (Reinur Schnur)
DRY_TIME in dist_prcp.c was incremented by the time step in
hours. Then to see if the current rain was part of the same
storm or the start of a new one, DRY_TIME was checked to see
if it was greater than or equal to 24/dt. This compares
DRY_TIME in hours to the model time step. The "/dt" has been
removed, so now DRY_TIME is checked versus the hours since the
last storm.
State file: (KAC)
*** WARNING: This may require modifications to your global file ***
The state file has been modified to account for model updates.
It has also been converted to write binary files - this makes
them less convenient to edit, but means that model starts using
the same forcing, soil and vegetation files will produce the
exact same results. There has also been a slight change in how
the global file is set up to restart the model. The global
file should now have the same year, month, day and hour as the
original global file - the VIC model will compute the number of
records to skip at the beginning to reach the point where the
model state was saved. This means that calculations to yield
sub-daily metrological forcings from daily forcings will produce
the exact same forcing values -> this also means that restarted
simulations will be exactly the same as the original run. Slight
variations in the model results were also introduced because the
method for storing soil node depths led to the possibility of
very small differences in dz_node for the restarted model.
Previous versions also did not store the snowpack cold content,
this meant that for restarts during winter, the snowpack albedo
might start on the ablation curve (as cold content was initialized
to 0 and not to a value less than 0) rather than the accumulation
curve. This could lead to slight differences in the snowpack
if no new snow fell and the snowpack was not melting - but
after 10 years of simulations the differences were minor. As
noted above the new version of the state file should allow the
model to be restarted and to produce exactly the same results as
the original complete result. If there are cases where this is
not true, please report. If you edit the read/write model state
functions - BE VERY CAREFUL to edit Nbytes to reflect any changes.
COMPUTE_TREELINE: (KAC and LCB)
This is an added feature which computes the treeline elevation
in the current grid cell and does not include vegetation
fractions with overstory in the grid cell averages for snow bands
that exceed the treeline elevation. This feature was added
to the model to reduce the appearance of "glaciers" in high
elevation snow bands. It computes average annual July air
temperatures using the temperature data from the atmospheric
forcing files (WARNING - elevation of treeline may change if
the period of forcing data used changes). It then lapses the
average annual July air temperature to locate the elevation
at which it equals 10C. This is assumed to be the treeline,
so vegetation types with overstory in snow bands with average
elevations higher than this, are excluded from the grid cell
average variables in put_data.c. For the time being full
energy and water balances are still computed for these
vegetation fractions, and no attempt is made to verify that
a snow band has a non-overstory vegetation type that can be
expanded to represent the coverage area lost due to the
exclusion of the overstory fraction.
August 15, 2000: VIC release 4.0.3
This release fixes a problem with the implementation of va_arg that
causes run time errors on some systems. Previous releases of the code
worked correctly on the LINUX and freeBSD systems where it was tested.
However on some systems (including Sun Ultra-2s) character variables
passed with va_arg are changed into integers so reading a character from
the argument list does not produce the value sent to the routine. The
character flags used by VIC to indicate if there is snow present and if
the frozen soil algorithm has been activated have now been converted to
integers, which should make the va_arg call work on all systems.
Also fixed in this release was a check in dist_prec.c to see if it is
still raining which actually used the memory address of the
precipitation variable rather than the daily value in the check.
MODIFIED FILES:
read_atmos_data.c - Fixed input file time step check
write_forcing_files.c - Added free statements for pointers
calc_surf_energy_bal.c - Converted char flags to int
dist_prec.c - Fixed logical statement error
frozen_soil.c - Converted char flags to int
func_surf_energy_bal.c - Converted char flags to int
initialize_atmos.c - Added flag for output forcing
vicNl.h - Converted char flags to int
vicNl_def.h - Converted char flags to int
July 19, 2000: VIC release 4.0.2
Two new pre-processor options have been added to VIC as well as minor
modifications to two subroutines.
If set to TRUE the NO_REWIND pre-processor option stops the VIC model from
rewinding the soil and vegetation parameter input files for each new grid
cell. This reduces run times but requires that all input files are in the
same order as the soil parameter file.
If set TRUE the OUTPUT_FORCE pre-processor option blocks off the main
model and only reads the provided forcing files. Once VIC has estimated
the missing forcing parameters the full forcing data set for the defined
simulation period is output to a series of gridded forcing files. The
gridded forcing files are written to the RESULTS directory defined in the
global control file with the prefix "full_data_". The new files are in
Binary or ASCII depending on the setting of BINARY_OUTPUT.
The error messages in get_global_param.c have been modified so that the
correct file is referenced when telling the user to change values found in
the model source code.
In read_soilparam.c, the soil parameters are defined only if the current
grid cell is run, otherwise the line in the file is skipped and soil_con
is returned without new data values.
May 30, 2000: VIC release 4.0.1
Increased use of the released VIC model code has lead to the
discovery of a couple of minor bugs. This release fixes those bugs as
well as introducing a improved precipitation correction algorithm based on
Yang et al. 1998. Unless you have encountered these problems or are
trying to correct precipitation undercatch due to wind, in the VIC
model, your results will not be impacted by these fixes.
MODIFIED FILES:
correct_precip.c - changed to WMO correction equation for
NWS 8" standard gauge.
full_energy.c - modified to handle WMO correction.
initialize_atmos.c - modified to handle WMO correction.
fixed error in estimating minimum daily
temperature from sub-daily temperatures.
make_in_and_outfiles.c - removed line that opened the state file
again for each new grid cell.
open_state_file.c - modified comments.
put_data.c - modified to handle WMO correction.
snow_utility.c - cleaned source code.
solve_snow.c - modified to handle WMO correction.
surface_fluxes.c - modified to handle WMO correction.
vicNl.h - modified to handle WMO correction.
vicNl_def.h - modified to handle WMO correction.
REFERENCE:
Yang, D., B. E. Goodison, J. R. Metcalfe, V. S. Golubev, R.
Bates, T. Pangburn, and C. L. Hanson, Accuracy of NWS 8" Standard
Nonrecording Precipitation Gauge: Results and Application of WMO
Intercomparison, J. Atmos. Oceanic Tech., 15, 54-68, 1998.
Date: May 16, 2000
From: Keith Cherkauer
Topic: Release of VIC 4.0.0
The code for VIC release 4.0.0 has undergone several months of tests (as
VIC release 3.3.0 Beta) and has now been deemed ready for release to the
general public. This document is designed to provide information
concerning changes in the model between the last release version (3.2.1)
and the current version.
There is no formal users manual, information about how to use the current
version can be found at
http://www.hydro.washington.edu/Lettenmaier/Models/VIC_old/VIChome.html.
Information about the basic model design can be found in Liang, et al.
(1994), while the rewrite of the source code as well as the addition of
cold season processes is described in Cherkauer and Lettenmaier (1999).
The VIC macroscale hydrologic model was developed as a research tool. As
such it is the users responsibility to verify that it is working correctly
when applied to new situations. When using the VIC model reference should
be made to Liang, et al. (1994) and Cherkauer and Lettenmaier (1999) as
well as an acknowledgment that the code was received from the University
of Washington. Other important papers relating to the development of the
VIC model are included on the home page and in the source code.
Possible bugs in the code should be reported to
vicadmin@hydro.washington.edu. ALWAYS CHECK YOUR INPUT FILES! Most
"bugs" are actually caused by trying to run the model with bad parameters
or forcing data. The VIC model will run limited checks to find common
major errors but in most cases it will attempt to run with the bad values.
If after checking all of your input data you still believe you have found
a bug in the model, send an e-mail including the complete output from the
model as well as a description of the problem and the files necessary to
run the model to recreate the code (if files are large please put a
compressed tar file in
ftp://ftp.ce.washington.edu/pub/HYDRO/vicadmin/TEMP). Outdated and
modified versions of the code are the responsibility of the user to debug.
Modifications made to the code, which may improve the general model
performance, may be submitted to vicadmin@hydro.washington.edu for
possible inclusion in future versions of the code.
VIC release 4.0.0 represents a major change to the source code from
version 3.2.1. It is strongly recommended that if you were using version
3.2.1 or earlier versions that you update with a complete copy of the new
code.
Major changes from release version 3.2.1 to 4.0.0:
- Radiation Estimation Update: The routines to estimate shortwave and
longwave radiation as well as vapor pressure from daily minimum and
maximum temperature and precipitation have been updated to correspond to
the algorithm described by Thornton and Running (1999). These routines
provide significantly improved radiation estimates especially in regions
outside the continental United States.
- Model Core Update: The core of the VIC model was rewritten so that all
modes of the model (water balance, energy balance, etc.) make use of the
same model code. This makes it easier to modify the model and have
modifications apply to sll modes, it also allows the model to run with new
combinations of algorithms (i.e. full energy balance mode with the finite
difference ground heat flux solution).
- Soil Moisture Transport Update: The frozen and thawed sub-layers added
to the model for the original frozen soil algorithm have been removed.
This makes the soil drainage routine cleaner and faster. Frozen soils now
estimate full layer ice contents from the ice content at each soil thermal
node. Without being confined by sub-layers, the frozen soil algorithm can
now be applied to regions of permafrost.
- Forcing File Control Added: Version 4.0.0 moves controls of the forcing
file format and data types into the global control file. The model can
now handle most ASCII column and short int Binary files without writing
new subroutines and recompiling the source code.
- Pre-processor Options Added: There are now more option flags in the
source code headers to control which parts of the model are in fact
compiled. This allows the model functionality to be adjusted without the
addition of computationally intensive conditional switching statements.
- Model State File: With the release of version 4.0.0 separate snow and
soil initialization files have been combined into a single model state
file. The state file can be created outside the model for starting
simulations with prescribed initial conditions, or the model state can be
saved by VIC at a specified date. Note that currently there will be small
differences between a full and a warm started simulation because radiation
and vapor pressure are estimated using forcing data from the simulation
period, not from the full dataset included in the forcing file. It also
does not store wet and dry fraction information, when running with
distributed precipitation the model is restarted using average soil
conditions.
References:
Liang, X., D. P. Lettenmaier, E. F. Wood, and S. J. Burges, A simple
hydrologically based model of land surface water and energy fluxes for
GSMs, J. Geophys. Res., 99(D7), 14,415-14,428, 1994.
Cherkauer, K. A., and D. P. Lettenmaier, Hydrologic effects of frozen
soils in the upper Mississippi River basin, J. Geophys. Res., 104(D16),
19,599-19,610, 1999.
Thornton, P.E. and S.W. Running, An improved algorithm for estimating
incident daily solar radiation from measurements of temperature, humidity,
and precipitation, Ag. For. Met., 93, 211-228, 1999.
File List:
CalcAerodynamic.c modify_Ksat.c
Makefile mtclim42_vic.c
SnowPackEnergyBalance.c mtclim42_vic.h
StabilityCorrection.c mtclim42_wrapper.c
alloc_atmos.c nrerror.c
arno_evap.c open_debug.c
calc_air_temperature.c open_file.c
calc_cloud_cover_fraction.c open_state_file.c
calc_longwave.c penman.c
calc_rainonly.c prepare_full_energy.c
calc_root_fraction.c put_data.c
calc_surf_energy_bal.c read_arcinfo_ascii.c
calc_veg_params.c read_atmos_data.c
canopy_evap.c read_forcing_data.c
check_files.c read_initial_model_state.c
check_state_file.c read_snowband.c
close_files.c read_soilparam.c
cmd_proc.c read_soilparam_arc.c
compress_files.c read_veglib.c
compute_dz.c read_vegparam.c
correct_precip.c redistribute_during_storm.c
dist_prec.c root_brent.c
estimate_T1.c runoff.c
free_dist_prcp.c snow.h
free_vegcon.c snow_intercept.c
frozen_soil.c snow_melt.c
full_energy.c snow_utility.c
func_surf_energy_bal.c soil_conduction.c
get_force_type.c soil_thermal_eqn.c
get_global_param.c solve_snow.c
global.h store_moisture_for_debug.c
initialize_atmos.c surface_fluxes.c
initialize_global.c svp.c
initialize_model_state.c user_def.h
initialize_new_storm.c vicNl.c
initialize_snow.c vicNl.h
initialize_soil.c vicNl_def.h
initialize_veg.c vicerror.c
make_cell_data.c write_atmosdata.c
make_dist_prcp.c write_data.c
make_dmy.c write_debug.c
make_energy_bal.c write_layer.c
make_in_and_outfiles.c write_model_state.c
make_snow_data.c write_soilparam.c
make_veg_var.c write_vegparam.c
massrelease.c write_vegvar.c