Unit conversions

Bigleaf.LE_to_ETFunction
LE_to_ET(LE,Tair)
ET_to_LE(ET,Tair)

Convert evaporative water flux from mass (ET=evapotranspiration) to energy (LE=latent heat flux) units, or vice versa.

Arguments

• LE Latent heat flux (W m-2)
• ET Evapotranspiration (kg m-2 s-1)
• Tair Air temperature (deg C)

Details

The conversions are given by:

• $ET = LE/\lambda$
• $LE = \lambda ET$

where $\lambda$ is the latent heat of vaporization (J kg-1) as calculated by latent_heat_vaporization.

Examples

# LE of 200 Wm-2 and air temperature of 25degC
ET = LE_to_ET(200,25)
≈(ET, 8.19e-5, atol =1e-7)
Bigleaf.ms_to_molFunction
ms_to_mol(G_ms,Tair,pressure; constants=bigleaf_constants())
mol_to_ms(G_mol,Tair,pressure; constants=bigleaf_constants())

Converts conductances from mass (m s-1) to molar units (mol m-2 s-1), or vice versa

Details

The conversions are given by

• $G_{mol} = G_{ms} \, pressure / (Rgas Tair)$
• $G_{ms} = G_{mol} \, (Rgas Tair) / pressure$

where Tair is in Kelvin and pressure in Pa (converted from kPa internally).

References

Jones, HG 1992_ Plants and microclimate: a quantitative approach to environmental plant physiology_ 2nd Edition, Cambridge University Press, Cambridge 428

Examples

G_ms,Tair,pressure = 0.005,25,100
rmol = ms_to_mol(G_ms,Tair,pressure)
≈(rmol, 0.2017, atol =1e-4)
Bigleaf.VPD_to_eFunction
VPD_to_rH(VPD,Tair; ...)
H_to_VPD(rH,Tair; ...)
e_to_rH(e,Tair; ...)
VPD_to_e(VPD,Tair; ...)
e_to_VPD(e,Tair; ...)
e_to_q(e,pressure; ...)
q_to_e(q,pressure; ...)
q_to_VPD(q,Tair,pressure; ...)
VPD_to_q(VPD,Tair,pressure; ...)

Conversion between vapor pressure (e), vapor pressure deficit (VPD), specific humidity (q), and relative humidity (rH).

Arguments

• Tair: Air temperature (deg C)
• pressure: Atmospheric pressure (kPa)
• e: Vapor pressure (kPa)
• q: Specific humidity (kg kg-1)
• VPD: Vapor pressure deficit (kPa)
• rH: Relative humidity (-)

All functions accept the optional arguemtns:

Rreferences

Foken, T, 2008: Micrometeorology_ Springer, Berlin, Germany.

Bigleaf.Rg_to_PPFDFunction
Rg_to_PPFD(Rg,J_to_mol=4.6,frac_PAR=0.5)
PPFD_to_Rg(PPFD,J_to_mol=4.6,frac_PAR=0.5)

Conversions between Global Radiation (W m-2) and Photosynthetic Photon Flux Density (umol m-2 s-1)

Arguments

• Rg: Global radiation = incoming short-wave radiation at the surface (W m-2)
• PPFD: Photosynthetic photon flux density (umol m-2 s-1)
• Jtomol: Conversion factor from J m-2 s-1 (= W m-2) to umol (quanta) m-2 s-1
• frac_PAR: Fraction of incoming solar irradiance that is photosynthetical- active radiation (PAR); defaults to 0.5

Details

The conversion is given by:

$PPFD = Rg * frac_PAR * J_to_mol$

by default, the combined conversion factor (frac_PAR * J_to_mol) is 2.3

Examples

# convert a measured incoming short-wave radiation of 500 Wm-2 to
# PPFD in umol m-2 s-1 and backwards
Rg_to_PPFD(500)
PPFD_to_Rg(1150)
Bigleaf.kg_to_molFunction
kg_to_mol(mass, molarMass=bigleaf_constants()[:H2Omol])

Conversion between Mass (kg) and Molar Units (mol).

Bigleaf.umolCO2_to_gCFunction
umolCO2_to_gC(CO2_flux; constants=bigleaf_constants())
gC_to_umolCO2(C_flux; constants=bigleaf_constants())

Convert CO2 quantities from (umol CO2 m-2 s-1) to (g C m-2 d-1) and vice versa.

Arguments

• CO2_flux CO2 flux (umol CO2 m-2 s-1)
• C_flux Carbon (C) flux (gC m-2 d-1)
• constants: dictionary from bigleaf_constants with entries: Cmol, umol2mol, mol2umol, kg2g, g2kg, says2seconds

Examples

umolCO2_to_gC(20)  # gC m-2 d-1