Core class for the Daymet functions.
- pydaymet.pet.potential_et(clm, coords=None, crs=DEF_CRS, method='hargreaves_samani', params=None)¶
Compute Potential EvapoTranspiration for both gridded and a single location.
Minimum temperature in degree celsius
Maximum temperature in degree celsius
Solar radiation in in W/m2
Daylight duration in seconds
Optionally, relative humidity and wind speed at 2-m level will be used if available.
Table below shows the variable names that the function looks for in the input data.
tmin (degrees C)
tmax (degrees C)
If relative humidity and wind speed at 2-m level are not available, actual vapour pressure is assumed to be saturation vapour pressure at daily minimum temperature and 2-m wind speed is considered to be 2 m/s.
floats, optional) – Coordinates of the daymet data location as a tuple, (x, y). This is required when
str, optional) – The spatial reference of the input coordinate, defaults to
epsg:4326. This is only used when
str, optional) – Method for computing PET. Supported methods are
hargreaves_samani, and None (don’t compute PET). The
penman_monteithmethod is based on Allen et al.1 assuming that soil heat flux density is zero. The
priestley_taylormethod is based on Priestley and TAYLOR2 assuming that soil heat flux density is zero. The
hargreaves_samanimethod is based on Hargreaves and Samani3. Defaults to
dict, optional) – Model-specific parameters as a dictionary, defaults to
Richard G Allen, Luis S Pereira, Dirk Raes, Martin Smith, and others. Crop evapotranspiration-guidelines for computing crop water requirements-fao irrigation and drainage paper 56. Fao, Rome, 300(9):D05109, 1998.
Charles Henry Brian Priestley and Robert Joseph TAYLOR. On the assessment of surface heat flux and evaporation using large-scale parameters. Monthly weather review, 100(2):81–92, 1972.
George H. Hargreaves and Zohrab A. Samani. Estimating potential evapotranspiration. Journal of the Irrigation and Drainage Division, 108(3):225–230, sep 1982. URL: https://doi.org/10.1061%2Fjrcea4.0001390, doi:10.1061/jrcea4.0001390.