pyet.radiation.hargreaves#
- pyet.radiation.hargreaves(tmean, tmax, tmin, lat, k=0.0135, method=0, clip_zero=True)[source]#
Potential evapotranspiration calculated according to Hargreaves and Samani (1982).
- Parameters:
tmean (pandas.Series or xarray.DataArray) – average day temperature [°C].
tmax (pandas.Series or xarray.DataArray) – maximum day temperature [°C].
tmin (pandas.Series or xarray.DataArray) – minimum day temperature [°C].
lat (float/xarray.DataArray) – the site latitude [rad].
k (float, optional) – calirbation coefficient [-].
method (float, optional) – 0 => after Jensen and Allen (2016) 1 => after McMahon et al. (2013).
clip_zero (bool, optional) – if True, replace all negative values with 0.
- Returns:
pandas.Series or xarray.DataArray containing the calculated potential
evapotranspiration [mm d-1].
Examples
>>> pet_har = hargreaves(tmean, tmax, tmin, lat)
Notes
Method = 0; Based on equation (8-16) in Jensen and Allen (2016).
\[PET = k \frac{R_a (T_{mean}+17.8)\sqrt{(T_{max}-T_{min})}} {\lambda}\]Method = 1; Based on McMahon et al. (2013).
\[PET = chs k \frac{R_a (T_{mean}+17.8)\sqrt{(T_{max}-T_{min})}} {\lambda}\], where
\[chs=0.00185*(T_{max}-T_{min})^2-0.0433*(T_{max}-T_{min})+0.4023\]