Model Constants and Miscellaneous Parameters

The VIC model requires the specification of many model parameters to run. While some parameters are spatially distributed (e.g. soil, vegetation, or snowbands), others are more appropriately held constant across the model domain.

Physical Constants

Physical constants are set in the vic_physical_constants.h header file. These constants rarely need to be changed and the model must be recompiled after any modifications.

Model Constants and Parameters

Some model constants and model parameters need to be changed more frequently. VIC supports this through the use of the optional CONSTANTS file. The path to this file should be specified in the global parameter file.

There are over 150 constants that can be changed through this file. An example CONSTANTS file is shown below.

# Set HUGE_RESIST to smaller value
HUGE_RESIST 1e5

# Set EMISS_GRND to unrealistic value
EMISS_GRND 0.3

The table below lists the constants available for manipulation via the CONSTANTS file. Descriptions will be added later or as needed. Default values can be found in initialize_parameters.c

Constant Description
LAPSE_RATE
GAUGE_HEIGHT
HUGE_RESIST
ALBEDO_BARE_SOIL
ALBEDO_H20_SURF
EMISS_GRND
EMISS_ICE
EMISS_VEG
EMISS_SNOW
EMISS_H2O
SOIL_RESID_MOIST
SOIL_SLAB_MOIST_FRACT
VEG_LAI_SNOW_MULTIPLIER
VEG_MIN_INTERCEPTION_STORAGE
VEG_LAI_WATER_FACTOR
CANOPY_CLOSURE
CANOPY_RSMAX
CANOPY_VPDMINFACTOR
LAKE_TMELT
LAKE_MAX_SURFACE
LAKE_BETA
LAKE_FRACMIN
LAKE_FRACLIM
LAKE_DM
LAKE_SNOWCRIT
LAKE_ZWATER
LAKE_ZSNOW
LAKE_RHOSNOW
LAKE_CONDI
LAKE_CONDS
LAKE_LAMISW
LAKE_LAMILW
LAKE_LAMSSW
LAKE_LAMSLW
LAKE_LAMWSW
LAKE_LAMWLW
LAKE_A1
LAKE_A2
LAKE_QWTAU
LAKE_MAX_ITER
SVP_A
SVP_B
SVP_C
PHOTO_OMEGA
PHOTO_LAIMAX
PHOTO_LAILIMIT
PHOTO_LAIMIN
PHOTO_EPAR
PHOTO_FCMAX
PHOTO_FCMIN
PHOTO_ZENITHMIN
PHOTO_ZENITHMINPAR
PHOTO_ALBSOIPARMIN
PHOTO_MINMAXETRANS
PHOTO_MINSTOMCOND
PHOTO_FCI1C3
PHOTO_FCI1C4
PHOTO_OX
PHOTO_KC
PHOTO_KO
PHOTO_EC
PHOTO_EO
PHOTO_EV
PHOTO_ER
PHOTO_ALC3
PHOTO_FRDC3
PHOTO_EK
PHOTO_ALC4
PHOTO_FRDC4
PHOTO_THETA
PHOTO_FRLEAF
PHOTO_FRGROWTH
SRESP_E0_LT
SRESP_T0_LT
SRESP_WMINFM
SRESP_WMAXFM
SRESP_WOPTFM
SRESP_RHSAT
SRESP_RFACTOR
SRESP_TAULITTER
SRESP_TAUINTER
SRESP_TAUSLOW
SRESP_FAIR
SRESP_FINTER
SNOW_MAX_SURFACE_SWE
SNOW_LIQUID_WATER_CAPACITY
SNOW_NEW_SNOW_DENSITY
SNOW_NEW_SNOW_DENS_MAX
SNOW_DEPTH_THRES
SNOW_DENS_DMLIMIT
SNOW_DENS_DMLIMIT_FACTOR
SNOW_DENS_MAX_CHANGE
SNOW_DENS_ETA0
SNOW_DENS_C1
SNOW_DENS_C2
SNOW_DENS_C3
SNOW_DENS_C3_CONST
SNOW_DENS_C4
SNOW_DENS_C4WET
SNOW_DENS_C5
SNOW_DENS_C6
SNOW_DENS_F
SNOW_DENS_EXP
SNOW_DENS_DENOM
SNOW_NEW_SNT_C1
SNOW_NEW_SNT_C2
SNOW_NEW_SNT_C3
SNOW_NEW_BRAS_DENOM
SNOW_MIN_SWQ_EB_THRES
SNOW_A1
SNOW_A2
SNOW_L1
SNOW_L2
SNOW_NEW_SNOW_ALB
SNOW_ALB_ACCUM_A
SNOW_ALB_ACCUM_B
SNOW_ALB_THAW_A
SNOW_ALB_THAW_B
SNOW_TRACESNOW
SNOW_CONDUCT
SNOW_MAX_SNOW_TEMP
SNOW_MIN_RAIN_TEMP
BLOWING_KA
BLOWING_CSALT
BLOWING_UTHRESH
BLOWING_KIN_VIS
BLOWING_MAX_ITER
BLOWING_K
BLOWING_SETTLING
BLOWING_NUMINCS
TREELINE_TEMPERATURE
SNOW_DT
SURF_DT
SOIL_DT
CANOPY_DT
CANOPY_VP
TOL_GRND
TOL_OVER
FROZEN_MAXITER
MAX_ITER_GRND_CANOPY
NEWT_RAPH_MAXTRIAL
NEWT_RAPH_TOLX
NEWT_RAPH_TOLF
NEWT_RAPH_R_MAX
NEWT_RAPH_R_MIN
NEWT_RAPH_RELAX1
NEWT_RAPH_RELAX2
NEWT_RAPH_RELAX3
NEWT_RAPH_EPS2
ROOT_BRENT_MAXTRIES
ROOT_BRENT_MAXITER
ROOT_BRENT_TSTEP
ROOT_BRENT_T