pydaymet.pet
Contents
pydaymet.pet
#
Core class for the Daymet functions.
Module Contents#
- pydaymet.pet.potential_et(clm, coords=None, crs=4326, method='hargreaves_samani', params=None)#
Compute Potential EvapoTranspiration for both gridded and a single location.
- Parameters
clm (
pandas.DataFrame
orxarray.Dataset
) – The dataset must include at least the following variables: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.
DataFrame
Dataset
tmin (degrees C)
tmin
tmax (degrees C)
tmax
srad (W/m2)
srad
dayl (s)
dayl
rh (-)
rh
u2m (m/s)
u2
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.
coords (
tuple
offloats
, optional) – Coordinates of the daymet data location as a tuple, (x, y). This is required whenclm
is aDataFrame
.crs (
str
,int
, orpyproj.CRS
, optional) – The spatial reference of the input coordinate, defaults toepsg:4326
. This is only used whenclm
is aDataFrame
.method (
str
, optional) – Method for computing PET. Supported methods arepenman_monteith
,priestley_taylor
,hargreaves_samani
, and None (don’t compute PET). Thepenman_monteith
method is based on Allen et al.1 assuming that soil heat flux density is zero. Thepriestley_taylor
method is based on Priestley and TAYLOR2 assuming that soil heat flux density is zero. Thehargreaves_samani
method is based on Hargreaves and Samani3. Defaults tohargreaves_samani
.params (
dict
, optional) – Model-specific parameters as a dictionary, defaults toNone
.
- Returns
pandas.DataFrame
orxarray.Dataset
– The input DataFrame/Dataset with an additional variable namedpet (mm/day)
for DataFrame andpet
for Dataset.
References
- 1
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.
- 2
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.
- 3
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.