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Glossary unit conversions

Michael Dietze edited this page Dec 7, 2020 · 1 revision

Glossary

Thermodynamic terms

  • Enthalpy. Total internal energy of thermodynamic system, plus the product of pressure and volume. Changes in enthalpy are equivalent to heat flux in closed systems at constant pressure.
  • Potential temperature. Temperature that any parcel would attain if it were adiabatically compressed or expanded to 105 Pa.
  • Triple point. Temperature and pressure conditions in which a substance can coexist as solid, liquid, and gas (vapour) and satisfy thermodynamic equilibrium. In the case of water, this occurs at 273.16 K and 6.12 Pa.

Constants

Variable Value
Molar mass of carbon 0.01201 kg mol-1
Molar mass of water 0.01801505 kg mol-1
Molar mass of dry air 0.02897 kg mol-1
Ein 2.17×10−5 J mol-1
Gravity acceleration 9.80665 m s-2
Density of liquid water 1000 kg m-3
Density of fresh snow 100 kg m-3
Triple point of water 273.16 K
Thermal conductivity of liquid water 0.57\ W m-1 K-1
Specific heat of ice 2093 J kg-1 K-1
Specific heat of water 4186 J kg-1 K-1
Specific heat of dry air (constant pressure) 1005 J kg-1 K-1
Specific heat of water vapour (constant pressure) 1859 J kg-1 K-1
Latent heat of melting 33400 J kg-1
Latent heat of vaporization (triple point) 2.5×106 J kg-1
Latent heat of sublimation (triple point) 2.834×106 J kg-1
Typical oxygen mixing ratio 0.209 mol O2 mol-1
Ideal gas constant 8.31451 J mol-1 K-1
Boltzmann constant 1.38065×10-23 m2 kg s-2 K-1
Avogrado's number 6.0221409×1023
Stefan-Boltzmann constant 5.6696e×10-8 W m-2 K-4
von Kármán constant 0.40

Useful Constants and Conversions

Temperature:

  • 0°C = 273.15 K

Pressure:

  • 1 Pa ≡ 1 N m-2
  • 1 Pa = 10−5 bar
  • 1 Pa = 9.8692×10−6 atm
  • 1 Pa = 7.5006×10−3 mmHG
  • 1 Pa = 145.04×10−6 psi

Moisture:

  • 1 mm = 1 L m-2
  • 1 mm = 1 kg m2

Latent heat:

  • 2272 J g-1 -> 1 mm day-1 = 2272000 W kg-1 / 86400 s day-1 = 26.2963 W m-2
  • 1 kg m-2 s-1 = 2272000 W m-2

Carbon Flux:

  • 1 μmol m-2 s-1 = 0.010368 tC ha-1 day-1
  • 1 μmol m-2 s-1 = 3.786912 tC ha-1 yr-1
  • 1 μmol m-2 s-1 = 1.2×10-8 kg m-2 s-1

Time:

  • 1 day = 86400 s
  • 1 day = 1440 min
  • 1 hour = 3600 s
  • 1 year = 365.2425 day
  • 1 year = 31556952 s

Biomass:

  • 1 kg m-2 = 10 tC ha-1