PCIC's heavily modified local version of VIC, which adds support for glacier mass balance calculation and output.

Minor fixes since last release:

Fixed use of CF conventions time units for NetCDF output
Fixed incorrect rounding off of 5th decimal place in netCDF output lat & lon (latitude & longitude) dimensions

VIC Glacier - usage notes

This document summarizes the changes in how the VIC Glacier release is invoked -- specifically changes to the global parameter file that the user needs to know about -- which has diverged somewhat from the original UW version.

Users can read the particular section pertaining to their current needs, or follow through this document from start to finish as an instructive example of how to carry out the following workflow:

read in forcing variables from a daily aggregated NetCDF forcing file, with standard variable names (with/without legacy type and multiplier parameters), and/or with custom names mapped to standard names
generate an hourly disaggregated forcing file, with/without custom output variable names
feed a previously generated hourly disaggregated forcing file into a VIC hydrological simulation

Some of the global parameter file snippets included show the new parameters related to glacier mass balance accumulation, which are fairly self-explanatory. To include additional available glacier-related variables in the NetCDF output of your hydrological simulation, add them to the Output Variables section of the global parameter file in the same way as other VIC variables. Documentation on the specifics of these output variables will be made available soon.

1. Reading in Standard and Custom Name-mapped Forcing File Variables

Users can now specify the variable names VIC should expect to see in a provided NetCDF forcing file (in case these are different from the 'standard' VIC input variable names). This applies to the read-in of both standard daily forcings and hourly disaggregated forcings (generated by VIC). This accomplished by using the following format for these particular parameters in the in the Forcing Files and Parameters section:

########################################################################
# Forcing Files and Parameters
########################################################################
#    ...
#    FORCING1    /path/to/forcing/file.nc
#    FORCE_FORMAT     NETCDF
#    FORCE_ENDIAN     LITTLE    
#    N_TYPES     <number of forcing variables>
#

To provide legacy VIC forcings with integer types and scaling multipliers, and no input forcing variable name mapping:

#    FORCE_TYPE      <standard VIC varname>     <type>     <multiplier>
#e.g. FORCE_TYPE    PREC    UNSIGNED    40

Or, to provide legacy VIC forcings as above, along with input forcing variable name mapping:

#    FORCE_TYPE      <standard VIC varname>     <type>     <multiplier>     <varname in forcing file>
#e.g. FORCE_TYPE    TMIN    SIGNED    100    tasmin

Or, to provide new VIC forcings (of float type by default), and no input forcing variable name mapping (this is likely the default case):

#    FORCE_TYPE      <standard VIC varname>
#e.g. FORCE_TYPE    TMAX

Or, to provide new VIC forcings (of float type by default) with input forcing variable name mapping:

#    FORCE_TYPE      <standard VIC varname>     <varname in forcing file>
#e.g. FORCE_TYPE      AIR_TEMP     ta

The default mappings within VIC of to expected variable names are as follows in Table 1.1:

Table 1.1: Default Forcing Variable Mappings

standard VIC varname	expected input forcing variable name	variable description
AIR_TEMP	tas	air temperature
ALBEDO	ALBEDO	surface albedo
CHANNEL_IN	CHANNEL_IN	incoming channel flow
CAT_M	CAT_M	atmospheric CO2 mixing ratio
CRAINF	CRAINF	convective rainfall
CSNOWF	CSNOWF	convective snowfall
DENSITY	DENSITY	atmospheric density
FDIR	FDIR	fraction of incoming shortwave that is direct
LONGWAVE	rlds	incoming longwave radiation
LSRAINF	LSRAINF	large-scale rainfall
LSSNOWF	LSSNOWF	large-scale snowfall
PREC	pr	total precipitation	*
PRESSURE	ps	atmospheric pressure
QAIR	huss	specific humidity
RAINF	RAINF	rainfall
REL_HUMID	rhs	relative humidity
SHORTWAVE	rsds	incoming shortwave radiation
SNOWF	prs	snowfall
TMAX	tasmax	maximum daily air temperature	*
TMIN	tasmin	minimum daily air temperature	*
TSKC	clt	cloud cover
VEGCOVER	VEGCOVER	partial vegetation cover fraction
VP	VP	atmospheric vapor pressures
WIND	wind	wind speed	*
WIND_E	uas	east component of wind speed
WIND_N	vas	north component of wind speed

Default values marked with an asterisk (*) are the standard set of daily forcings provided in forcings_v2_1950-2006.nc.

2. Generating Disaggregated Forcings (OUTPUT_FORCE=TRUE)

In order to run VIC in meteorological disaggregation mode, i.e. to generate your own hourly forcing file, make the following changes to the global parameters file:

2.1

Move the OUTPUT_FORCE line to the bottom of the Simulation Parameters section and set it to TRUE (Note: old global files will have OUTPUT_FORCE located in the Output Files and Parameters section; cut and paste it from there to the end of Simulation Parameters, as the order that VIC reads global parameters now matters).

2.2

Change TIME_STEP to 1 (hourly), rather than 24, to indicate that the simulation will be run at hourly time steps.

For example:

########################################################################
# Simulation Parameters
########################################################################
TIME_STEP       1
SNOW_STEP       1
STARTYEAR       1960     # year to begin generating forcings for (this will be the start year in the output file)
END_YEAR        1995     # last year to generate forcings for 
...
GLACIER_ID      22
GLACIER_ACCUM_START_YEAR        1970
GLACIER_ACCUM_START_MONTH       10
GLACIER_ACCUM_START_DAY         1
GLACIER_ACCUM_INTERVAL          1
OUTPUT_FORCE    TRUE     # indicates to VIC that it should only generate hourly forcing data, then exit (no hydrological simulation is executed)

2.3

In the Output Files and Parameters section, specify where you want the disaggregated forcings output file to be written, and optionally, the NETCDF_OUTPUT_FILENAME to give it in that location (if this parameter is not provided, the default filename will be results.nc). Specify the output time step size, OUT_STEP, as 1 for hourly, or 3 if you want output in 3-hour intervals, etc. (if this is left as 0, VIC will default to using the value given for the TIME_STEP parameter).

For example:

########################################################################
# Output Files and Parameters
########################################################################
RESULT_DIR /path/to/my/generated/disaggregated/forcing/file
NETCDF_OUTPUT_FILENAME hourly_disagg_forcings.nc
OUT_STEP 1

2.4

Optionally, provide mapping of output forcing variable names. If no mapped name is provided, the format will be used for the NetCDF variable name (e.g. OUT_WIND in the following example will result in the NetCDF variable name WIND in the output disaggregated forcings file). Note that N_OUTFILES, OUTFILE, and the value given are all ignored if the output file format is set to NetCDF, but still must be set correctly to the number of variables to be written (i.e. the number of OUTVAR lines to follow). These mapped forcings output variable names will be those that VIC will have to read in when you use the hourly forcings NetCDF file later as input to your simulation. If you choose the default mapping given in Table 1.1, VIC will recognize these as valid forcing inputs. If not, you will have to set the input forcing mappings accordingly, as shown in Section 3.2 (in this example, my_shortwave_varname would not be recognized by default as a valid forcing variable).

For example:

########################################################################
# Output Variables
#
# Format:
#
# N_OUTFILES <n_outfiles>
# OUTFILE <prefix> <nvars>
# OUTVAR <varname> [<output_varname>]
# OUTVAR <varname> [<output_varname>]
# OUTVAR <varname> [<output_varname>]
#########################################################################

For example:

# OUTFILE    cell    8 
# OUTVAR    OUT_PREC    pr
# OUTVAR    OUT_AIR_TEMP    ta
# OUTVAR    OUT_SHORTWAVE    my_shortwave_varname
# OUTVAR    OUT_LONGWAVE    rlds
# OUTVAR    OUT_DENSITY    DENSITY  
# OUTVAR    OUT_PRESSURE    ps
# OUTVAR    OUT_VP    VP
# OUTVAR    OUT_WIND  # providing no mapping here will result in the standard VIC name "WIND" being used as the variable name in the output NetCDF. Note that the default forcing variable name VIC expects to read in is "wind". More on how to deal with this is given in Section 3.2.

3. Feeding Hourly Disaggregated Forcings into VIC

Time-major NetCDF forcing files generated by VIC in meteorological disaggregator mode (OUTPUT_FORCE=TRUE), being by default at hourly time steps, can be used as inputs to VIC in normal simulation run mode (OUTPUT_FORCE=FALSE).

To support reading of hourly disaggregated forcings into VIC, make the following modifications to the global parameter file:

3.1

In the Simulation Parameters section, declare the TIME_STEP (hourly forcings means hourly simulation time step, thus TIME_STEP=1) and start/end years of the simulation to be run, and provide the OUTPUT_FORCE (set to FALSE) parameter at the end of this section (**Note: old global files will have OUTPUT_FORCE in the...

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VIC Glacier - usage notes

1. Reading in Standard and Custom Name-mapped Forcing File Variables

Table 1.1: Default Forcing Variable Mappings

2. Generating Disaggregated Forcings (OUTPUT_FORCE=TRUE)

2.1

2.2

2.3

2.4

3. Feeding Hourly Disaggregated Forcings into VIC

3.1

Releases: pacificclimate/VIC

VIC Glacier

VIC Glacier - usage notes

1. Reading in Standard and Custom Name-mapped Forcing File Variables

Table 1.1: Default Forcing Variable Mappings

2. Generating Disaggregated Forcings (OUTPUT_FORCE=TRUE)

2.1

2.2

2.3

2.4

3. Feeding Hourly Disaggregated Forcings into VIC

3.1

VIC Glacier