A collection of functions to convert between relative humidity (RH) (%),
vapour pressure deficit (VPD) (kPa),
dew point temperature, and leaf- or air temperature-based VPD or RH. To convert from
relative humidity to VPD,
use the RHtoVPD function, use VPDtoRH for the other way around. The water
vapor saturation pressure is
calculated with esat. Use DewtoVPD to
convert from dewpoint temperature to VPD. The functions VPDleafToAir and VPDairToLeaf
convert VPD from a leaf temperature to an air-temperature basis and vice versa. The
functions RHleafToAir a RHairToLeaf do the same for relative humidity.
RHtoVPD(RH, TdegC, Pa = 101) VPDtoRH(VPD, TdegC, Pa = 101) esat(TdegC, Pa = 101) VPDtoDew(VPD, TdegC, Pa = 101) DewtoVPD(Tdew, TdegC, Pa = 101) VPDleafToAir(VPD, Tleaf, Tair, Pa = 101) VPDairToLeaf(VPD, Tair, Tleaf, Pa = 101) RHleafToAir(RH, Tleaf, Tair, Pa = 101) RHairToLeaf(RH, Tair, Tleaf, Pa = 101)
| RH | Relative humidity (%) |
|---|---|
| TdegC | Temperature (degrees C) (either leaf or air) |
| Pa | Atmospheric pressure (kPa) |
| VPD | Vapour pressure deficit (kPa) |
| Tdew | Dewpoint temperature (degrees C) |
| Tleaf | Leaf temperature (degrees C) |
| Tair | Air temperature (degrees C) |
The function describing saturated vapor pressure with temperature is taken from Jones (1992). All other calculations follow directly from the standard definitions, for which Jones (1992) may also be consulted.
Jones, H.G. 1992. Plants and microclimate: a quantitative approach to environmental plant physiology. 2nd Edition., 2nd Edn. Cambridge University Press, Cambridge. 428 p.