Name

Default

Unit

Symbol

Comments/Explanation

Absolute zero

-273.15

°C

T_abszero

Biomass to carbon

0.45

mol C/g dw

η

Conversion of biomass (g dw) to carbon (mol C)

Density of air

1.220

kg/m³

ρ_a

At 20 °C.

Density of solid soil

2.65

kg/m³

ρ_s

Density of water

1000

kg/m³

ρ_water

Diffusion rate of oxygen

2.6e-5

m²/s

o_O2diffrate

At 20 ˚C.

Gas constant

8.31

J/K/ mol

R

Gravitational constant

9.81

m/s²

g

Karmans constant

0.41

-

k

Used in the calculation of aerodynamic resistance.

Latent heat of freezing

3.34e5

J/kg

L_f

The energy required to melt 1 kg of ice.

Latent heat of sublimation

2.84e6

J/kg

L_s

The energy required to vapourize 1 kg of ice.

Latent heat of vaporization

2.45e6

J/kg

L_v

The energy required to vapourize 1 kg of liquide water.

Molar Mass, Carbon

12.011

g/mol

M_C

Molar Mass, Carbondioxide

44.0098

g/mol

M_CO2

Molar Mass, Dry air

29.0

g/mol

M_Air

Molar Mass, Oxygen

31.998

g/mol

M_O2

Molar Mass, Salt

35.4527

g/mol

M_Cl

Cloride mass only.

Molar Mass, Water

18.016

g/mol

M_water

Molar ratio, Oxygen to Air

1.10

-

o_ratioair

Molar ratio, Oxygen to Carbon

2.664058

-

o_ratioC

Mole air per cubic meter

44.6

mol/m³

a_mol

Normal atmospheric pressure at soil surface

1.013e5

Pa

p_atmnorm

Partial pressure of oxygen in the atmosphere

20.5e3

Pa

O

Psycrometric constant

66

Pa/°C

γ

Used in the calculation of potential transpiration.

Specific heat of air

1.004

J/g/°C

c_p

At 15 °C. The amount of enegy required to raise the temperature of 1 g of air 1 °C.

Specific heat of ice

2.1

J/g/°C

C_i

The amount of enegy required to raise the temperature of 1 g of ice 1 °C.

Specific heat of water

4.18

J/g/°C

C_w

The amount of enegy required to raise the temperature of 1 g of water 1 °C.

Specific volumetric heat capacity of solid soil

2e6

J/m³/°C

C_s

The amount of enegy required to raise the temperature of 1 m³ of the soil 1 °C.

Stefan-Boltzmann’s constant

5.67e-8

W/m²/K⁴

σ

Temperature of a completely frozen soil

-6

°C

T_f

Below this temperature the soil is regarded as completely frozen.