I need to compute vapour pressure deficit (VPD) from ECMWF ERA-5 data set.
Can anyone help me to select appropriate ERA-5 parameters and corresponding equations ?
You can get the list of available parameters here: https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels?tab=form
My first guess would be:
VPD = SVP – AVP
with AVP = actual vapor pressure
SVP = saturation vapor pressure
using formulation of Bougeault (1982):
SVP = 610.78 x e^(17.2694 x (Td-273.16) / (Td-35.86))
AVP = 610.78 x e^(17.2694 x (T -273.16) / (T -35.86))
With T = air temperature ("2m temperature" ERA5 parameter)
Td = dewpoint temperature ("2m dewpoint temperature " ERA5 parameter)
if correct, VPD is thus derived from T and Td
Thanks for helping
VPD = es(T) - es(Td)
where es is saturation vapor pressure calculated with the equation you wrote, or Magnus equation, or any other similar.
Just be careful with the equation you use, you have to know what is the unit for VPD in that case, and if there are different values of parameters for the temperatures above and below zero that you have to use in calculations
Hi Martin Claverie ,
Did you attempt this? I am interested in doing something similar using ERA5, and have the same derivation. I would likely want to take mean daily temperature and dewpoint temperature to get a mean daily VPD. Were you successful?
Thanks,
Mark
Hi Mark Pickering & Martin Claverie , I also need to calculate VPD from ERA5 data. I was wondering if you managed this? I'm unclear on what the units of VPD are from Martin's original formula, and whether I do need a different formula for temperatures above and below zero.
Hi all,
The function DewtoVPD() (R package plantecophys) also allows a quick calculation of VPD, using dewpoint temperature at 2m (2d) and temperature at 2m (2t) from ERA5-Land. RHtoVPD, for VPD from relative humidity and temperature, etc (see ?RHtoVPD for other options).
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