pyet.temperature.hamon

pyet.temperature.hamon(tmean, lat, k=1, c=13.97, cc=218.527, n=None, tmax=None, tmin=None, method=0, clip_zero=True)

Potential evapotranspiration calculated according to Hamon (1963).

Parameters:

• tmean (pandas.Series or xarray.DataArray) – average day temperature [°C].

• lat (float or xarray.DataArray) – the site latitude [rad].

• k (float, optional) – calibration coefficient if method = 0 [-].

• c (float, optional) – c is a constant for calculation in mm per day if method = 1.

• cc (float, optional) – calibration coefficient if method = 2 [-].

• n (float or pandas.Series or xarray.DataArray, optional) – actual duration of sunshine [hour].

• tmax (float or pandas.Series or xarray.DataArray) – maximum day temperature [°C].

• tmin (float or pandas.Series or xarray.DataArray) – minimum day temperature [°C].

• method (float, optional) – 0 => Hamon after Oudin et al. (2005) 1 => Hamon after equation 7 in Ansorge and Beran (2019) 2 => Hamon after equation 12 in Ansorge and Beran (2019). 3 => Hamon after equation 12 in Rosenberry et al. (2004).

• clip_zero (bool, optional) – if True, replace all negative values with 0.

Returns:

• float or pandas.Series or xarray.DataArray containing the calculated potential

• evapotranspiration [mm d-1].

Examples

>>> pet_hamon = hamon(tmean, lat)

Notes

Method = 0; Based on cite:t:oudin_which_2005.

\[PET = k(\frac{DL}{12})^2 exp(\frac{T_{mean}}{16})\]

Method = 1; Based on equation 7 in cite:t:ansorge_performance_2019.

\[PET = c(\frac{DL}{12})^2 pt\]

where

\[pt = 4.95 \frac{exp(0.062T_{mean})}{16}\]

Method = 2; Based on equation 12 in cite:t:ansorge_performance_2019.

\[PET = cc\frac{DL}{12} \frac{1}{T_{mean} + 273.3} exp(\frac{17.27T_{mean}}{T_{mean} + 273.3})\]

Method = 3; Based on cite:t:rosenberry_comparison_2004.

\[PET = 14 * (n / 12) ** 2 * (216.7 * e_s * 10 / (T_{mean} + 273.3)) / 100\]