Common Characteristics

List of constants

 

Name

Default

Unit

Symbol

Comments/Explanation

Absolute zero

-273.15

°C

Tabszero

 

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

ρa

At 20 °C.

Density of solid soil

2.65

kg/m3

ρs

 

Density of water

1000

kg/m3

ρwater

 

Diffusion rate of oxygen

2.6e-5

m2/s

oO2diffrate

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

Lf

The energy required to melt 1 kg of ice.

Latent heat of sublimation

2.84e6

J/kg

Ls

The energy required to vapourize 1 kg of ice.

Latent heat of vaporization

2.45e6

J/kg

Lv

The energy required to vapourize 1 kg of liquide water.

Molar Mass, Carbon

12.011

g/mol

MC

 

Molar Mass, Carbondioxide

44.0098

g/mol

MCO2

 

Molar Mass, Dry air

29.0

g/mol

MAir

 

Molar Mass, Oxygen

31.998

g/mol

MO2

 

Molar Mass, Salt

35.4527

g/mol

MCl

Cloride mass only.

Molar Mass, Water

18.016

g/mol

Mwater

 

Molar ratio, Oxygen to Air

1.10

-

oratioair

 

Molar ratio, Oxygen to Carbon

2.664058

-

oratioC

 

Mole air per cubic meter

44.6

mol/m3

amol

 

Normal atmospheric pressure at soil surface

1.013e5

Pa

patmnorm

 

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

cp

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

Ci

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

Cw

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

Cs

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

Tf

Below this temperature the soil is regarded as completely frozen.