geocat.comp.crop.saturation_vapor_pressure(temperature, tfill=nan)

Compute saturation vapor pressure as described in the Food and Agriculture Organization (FAO) Irrigation and Drainage Paper 56 entitled:

Crop evapotranspiration - Guidelines for computing crop water requirement. Specifically, see equation 11 of Chapter 3.

This is Tetens’ Formula: an empirical expression for saturation vapor pressure with respect to liquid water that includes the variation of latent heat with temperature.

Note that if temperature = tdew, then this function computes actual vapor pressure.


svp – the computed actual saturation vapor pressure in kPa. Same shape as temperature.

Return type

numpy.ndarray, xarray.DataArray


>>> import numpy as np
>>> from geocat.comp import saturation_vapor_pressure
>>> temp = np.array([50, 60, 70])
>>> saturation_vapor_pressure(temp)
array([1.22796262, 1.76730647, 2.50402976])

See also

Related GeoCAT Functions: actual_saturation_vapor_pressure, saturation_vapor_pressure_slope

Related NCL Functions: satvpr_temp_fao56