Physical constants¶
veris.model.physical_constants.PHYSICALCONSTANTS defines the values used by
the frozen PhysicalConstants dataclass, a collection whose fields cannot be
reassigned. These include physical coefficients (numbers used in equations), coefficients based on
observations, physical limits, scales that keep equations well behaved, and
reference heights for atmospheric forcing, the supplied air conditions. Each model initialization creates
its own constants object. Physical constants form a separate frozen PyTree:
independent values are dynamic leaves, dtype is static, and derived laws are
recomputed rather than fitted independently. They do not add fields to State.
Use dataclasses.replace for authored host values, or with_overrides for
tracer-safe physical continuations. Values calculated from
exact relationships, such as density ratios, follow the changed base values:
from dataclasses import replace
from veris.model.physical_constants import PhysicalConstants
constants = replace(PhysicalConstants(), rhoIce=920.0)
assert constants.rhoIce2rhoSnow == 920.0 / constants.rhoSnow
Parameterizations are formulas that approximate physical processes. Their
independently rounded coefficients keep their numerical defaults. Similar
names do not mean that formulas are interchangeable. Ice-removal thresholds
such as hIce_min, thresholds for drag against the seabed such as
basalDragMinArea, and minimum wind speeds in bulk-flux formulas (formulas for
transfer between surface and air) belong here because they define these
physical approximations. Supply constants={...}
in an Experiment, or replace fields on
PhysicalConstants. The low-level
veris.execution.initialization.initialize() instead uses
physical_overrides.
pressReplFac weights the replacement pressure that depends on strain (ice
deformation) in the law relating ice stress to deformation. Its default remains
1.0. Fractional values change that weight continuously. Set it through the same
constants group or by creating an updated constants object.
evpStressRelaxation and evpShearRelaxation also belong here. The first
scales the equilibrium stresses. Their ratio scales the equilibrium deviatoric
stresses, the part of stress that changes shape rather than volume. The two
values keep independent defaults. EVP means elastic-viscous-plastic, the method
used to solve for ice velocity and stress. Its numerical relaxation rates
evpAlpha and evpBeta remain model settings.
Registry defaults¶
Constant |
Default |
Unit |
Description |
|---|---|---|---|
|
|
|
Weight of strain-dependent replacement pressure in the ice constitutive law |
|
|
|
Stress damping coefficient setting the EVP constitutive equilibrium |
|
|
|
Deviatoric stress forcing coefficient setting the EVP constitutive equilibrium |
|
|
\(W/m^2\) |
minimum downward longwave radiation |
|
|
\({}^\circ\,C\) |
maximum ice temperature |
|
|
\({}^\circ\,C\) |
minimum ice temperature |
|
|
\({}^\circ\,C\) |
minimum air temperature |
|
|
|
Squared ice-concentration regularization (dimensionless) |
|
|
\(m^2\) |
regularization value for the ice thickness |
|
|
\(m/s\) |
minimum wind speed |
|
|
\(m\) |
‘minimum’ ice thickness |
|
|
|
‘minimum’ ice cover fraction |
|
|
\(kg/(m^2\,s)\) |
minimum of linear ice-ocean drag coefficient |
|
|
|
factor to scale sea ice loading |
|
|
\(s^{-1}\) |
Minimum strain-rate invariant |
|
|
\(m/s\) |
minimum atm. wind speed over ocean surface |
|
|
\(m/s\) |
minimum atm. wind speed over ice surface |
|
|
\(m\) |
reference height for wind speed |
|
|
\(m\) |
reference height for air temperature |
|
|
\(m\) |
Minimum actual ice thickness used in thermodynamic growth |
|
|
\(m^{-1}\) |
Inverse thickness scale of the basal-drag smooth positive part |
|
|
|
Minimum ice concentration that enables basal drag |
|
|
|
Maximum absolute height-to-Obukhov-length ratio |
|
|
\(m\,s^{-1}\) |
Minimum open-ocean wind speed in LANL bulk fluxes |
|
|
\(m\) |
Snow thickness at the transition to optically opaque snow albedo |
|
|
\(kg/m^3\) |
density of ice |
|
|
\(kg/m^3\) |
density of fresh water |
|
|
\(kg/m^3\) |
density of sea water |
|
|
\(kg/m^3\) |
density of air |
|
|
\(kg/m^3\) |
density of snow |
|
|
\(m^3/kg\) |
1 / rhoFresh |
|
|
\(m^3/kg\) |
1 / rhoSea |
|
|
|
Ice-to-snow density ratio (dimensionless) |
|
|
|
Ice-to-freshwater density ratio (dimensionless) |
|
|
|
Freshwater-to-snow density ratio (dimensionless) |
|
|
|
albedo of dry ice |
|
|
|
albedo of dry ice in the southern hemisphere |
|
|
|
albedo of wet ice |
|
|
|
albedo of wet ice in the southern hemisphere |
|
|
|
albedo of dry snow |
|
|
|
albedo of dry snow in the southern hemisphere |
|
|
|
albedo of wet snow |
|
|
|
albedo of wet snow in the southern hemisphere |
|
|
\({}^\circ\,C\) |
temperature above which the wet albedos are used |
|
|
\(J/kg\) |
latent heat of fusion |
|
|
\(J/kg\) |
latent heat of evaporation |
|
|
\(J/kg\) |
latent heat of sublimation |
|
|
\(J/(kg\,K)\) |
heat capacity of air |
|
|
\(J/(kg\,K)\) |
heat capacity of water |
|
|
\(W/m^2/K^4\) |
Stefan-Boltzmann constant |
|
|
|
longwave ice emissivity |
|
|
|
longwave snow emissivity |
|
|
\(W/m/K\) |
Sea ice thermal conductivity |
|
|
\(W/m/K\) |
Snow thermal conductivity |
|
|
|
shortwave ice penetration factor |
|
|
\({}^\circ\,C\) |
freezing temperature |
|
|
\({}^\circ\,C/(g/kg)\) |
Derivative of freezing temperature with respect to salinity |
|
|
\(g/kg\) |
reference salinity of sea ice |
|
|
|
Dalton number for sensible and latent heat transfer |
|
|
\(K\) |
Offset added to Celsius temperature to obtain kelvin |
|
|
|
stanton number |
|
|
\(m/s\) |
typical friction velocity beneath sea ice |
|
|
|
tapering factor at the ice bottom |
|
|
\(m\) |
Lead-closing ice thickness |
|
|
\(m^{-1}\) |
1 / h0 |
|
|
\(m\) |
Lead-closing ice thickness in the southern hemisphere |
|
|
\(m^{-1}\) |
1 / h0_south |
|
|
\({}^\circ\) |
turning angle of air-ice stress |
|
|
\({}^\circ\) |
turning angle of water-ice stress |
|
|
|
sin of waterTurnAngle |
|
|
|
cos of waterTurnAngle |
|
|
|
air-ice drag coefficient |
|
|
|
air-ice drag coefficient in the southern hemisphere |
|
|
|
water-ice drag coefficient |
|
|
|
water-ice drag coefficient in the southern hemisphere |
|
|
\(m/s^2\) |
gravitational acceleration |
|
|
|
axes ratio of the elliptical yield curve |
|
|
\(Pa\) |
sea ice strength parameter |
|
|
|
sea ice strength parameter |
|
|
\(m/s\) |
basal drag parameter |
|
|
|
basal drag parameter |
|
|
\(Pa/m\) |
Basal stress per unit keel excess thickness |
|
|
|
basal drag parameter |
|
|
|
sea ice tensile strength factor |
|
|
\(m/s^2\) |
Coastal drag acceleration coefficient |
|
|
\(m/s\) |
side drag critical velocity |
|
|
\(J/K/molecule\) |
Boltzmann’s constant |
|
|
\(molecules/kmole\) |
Avogadro number |
|
|
\(J/K/kmole\) |
avogad * bolzc - Ideal gas constant |
|
|
\(kg/kmole\) |
molecular weight of dry air |
|
|
\(kg/kmole\) |
molecular weight water vapor |
|
|
\(J/K/kg\) |
RGAS / MWDAIR - dry air gas constant |
|
|
\(J/K/kg\) |
RGAS / MWWV - water vapor constant |
|
|
|
(RWV / RDAIR) - 1.0 - Dry-air water-vapor molecular mass ratio |
|
|
\(J/K/kg\) |
specific heat of dry air |
|
|
\(J/K/kg\) |
specific heat of water vapor |
|
|
|
Humidity correction to dry-air specific heat (cpwv / cpdair - 1) |
|
|
|
von Karman constant |
|
|
\(J/kg\) |
latent heat of evaporation |
|
|
\(Pa\) |
reference pressure to compute potential temperature |
|
|
|
R/Cp |
|
|
\(m\) |
ice surface roughness |
|
|
|
bulk transfer coefficient for sensible heat |
|
|
|
bulk transfer coefficient for latent heat |
|
|
|
surface emissivity |
|
|
|
ocean surface emissivity |
|
|
|
snow surface emissivity |
|
|
|
ice surface emissivity |
|
|
\(K\) |
freezing temp of fresh water |
|
|
\({}^\circ\,C/m\) |
adiabatic lapse rate |
|
|
|
ocean albedo |
|
|
|
ice albedo |
|
|
\(m\) |
Mean spherical Earth radius used by geopotential-height conversion |
|
|
\(K\) |
Ice saturation vapor-pressure inverse-temperature coefficient |
|
|
|
Ice saturation vapor-pressure base-10 logarithmic offset |
|
|
|
Water-vapor to dry-air molecular mass ratio in saturation laws |
|
|
\(Pa\) |
Fixed pressure for the ice-surface humidity parameterization |
|
|
\(m^{-1}\) |
Exponential shortwave attenuation coefficient within ice |
|
|
|
Ice concentration scale of the McPhee bottom-melt taper |
|
|
|
McPhee bottom-melt taper numerator, divided by McPheeTaperArea |
|
|
|
Lateral concentration-loss factor multiplying reciprocal ice thickness |
|
|
\(kg\,m^{-3}\) |
CESM exponential saturation specific-humidity scale |
|
|
\(K\) |
CESM saturation humidity inverse-temperature coefficient |
|
|
|
August saturation vapor-pressure logarithmic offset |
|
|
\(K\) |
August saturation vapor-pressure inverse-temperature coefficient |
|
|
\(Pa\,mmHg^{-1}\) |
Conversion from millimetres of mercury to pascals |
|
|
\(m\,s^{-1}\) |
Reciprocal-wind coefficient in the neutral ocean drag law |
|
|
|
Constant coefficient in the neutral ocean drag law |
|
|
\(s\,m^{-1}\) |
Linear-wind coefficient in the neutral ocean drag law |
|
|
|
Historically rounded CESM unstable momentum angle offset |
|
|
\(hPa\) |
Humidity pressure scale in the ocean longwave parameterization |
|
|
|
Clear-sky offset in the ocean longwave parameterization |
|
|
\(hPa^{-0.5}\) |
Humidity coefficient in the ocean longwave parameterization |
|
|
|
Salinity reduction factor for ocean surface saturation humidity |
|
|
|
CESM unstable neutral heat-transfer square-root coefficient |
|
|
|
CESM stable neutral heat-transfer square-root coefficient |
|
|
|
CESM neutral moisture-transfer square-root coefficient |
|
|
|
Unstable Monin-Obukhov similarity coefficient |
|
|
|
Magnitude of the negative stable similarity coefficient |
|
|
|
LANL saturation specific-humidity scale |
|
|
\(kg\,J^{-1}\) |
LANL saturation exponent offset multiplying latent heat |
|
|
\(K\,kg\,J^{-1}\) |
LANL inverse-temperature exponent coefficient multiplying latent heat |
|
|
\(hPa\) |
LANL humidity reference pressure in its original hPa convention |
|
|
\({}^\circ\mathrm{N}\) |
Latitude knots for the ocean longwave cloud correction |
|
|
|
Cloud correction coefficients corresponding to latitude knots |