landlab.components.pet.potential_evapotranspiration_field

class PotentialEvapotranspiration[source]

Bases: Component

Potential Evapotranspiration Component calculates spatially distributed potential evapotranspiration based on input radiation factor (spatial distribution of incoming radiation) using chosen method such as constant or Priestley Taylor. Ref: Xiaochi et. al. 2013 for ‘Cosine’ method and ASCE-EWRI Task Committee Report Jan 2005 for ‘PriestleyTaylor’ method. Note: Calling ‘PriestleyTaylor’ method would generate/overwrite shortwave & longwave radiation fields.

Code author: Sai Nudurupati and Erkan Istanbulluoglu

Examples

>>> from landlab import RasterModelGrid
>>> from landlab.components.pet import PotentialEvapotranspiration

>>> grid = RasterModelGrid((5, 4), xy_spacing=(0.2, 0.2))
>>> grid["cell"]["radiation__ratio_to_flat_surface"] = np.array(
...     [0.38488566, 0.38488566, 0.33309785, 0.33309785, 0.37381705, 0.37381705]
... )
>>> PET = PotentialEvapotranspiration(grid)
>>> PET.name
'PotentialEvapotranspiration'
>>> PET.input_var_names
('radiation__ratio_to_flat_surface',)
>>> sorted(PET.output_var_names)
['radiation__incoming_shortwave_flux',
 'radiation__net_flux',
 'radiation__net_longwave_flux',
 'radiation__net_shortwave_flux',
 'surface__potential_evapotranspiration_rate']
>>> sorted(PET.units)
[('radiation__incoming_shortwave_flux', 'W/m^2'),
 ('radiation__net_flux', 'W/m^2'),
 ('radiation__net_longwave_flux', 'W/m^2'),
 ('radiation__net_shortwave_flux', 'W/m^2'),
 ('radiation__ratio_to_flat_surface', 'None'),
 ('surface__potential_evapotranspiration_rate', 'mm')]
>>> PET.grid.number_of_cell_rows
3
>>> PET.grid.number_of_cell_columns
2
>>> PET.grid is grid
True
>>> pet_rate = grid.at_cell["surface__potential_evapotranspiration_rate"]
>>> np.allclose(pet_rate, 0.0)
True
>>> PET.current_time = 0.5
>>> PET.update()
>>> np.allclose(pet_rate, 0.0)
False

References

Required Software Citation(s) Specific to this Component

None Listed

Additional References

ASCE-EWRI: The ASCE standardized reference evapotranspiration equation, in: Standardization of Reference Evapotranspiration Task Committee Final Report, edited by: Allen, R. G., Walter, I. A., Elliot, R. L., Howell, T. A., Itenfisu, D., Jensen, M. E., and Snyder, R. L., Technical Committee report to the Environmental and Water Resources Institute of the American Society of Civil Engineers from the Task Committee on Standardization of Reference Evapotranspiration, Reston, VA, USA, 2005.

Zhou, X., Istanbulluoglu, E., and Vivoni, E. R.: Modeling the ecohydrological role of aspect-controlled radiation on tree-grass-shrub coexistence in a semiarid climate, Water Resour. Res., 49, 2872– 2895, doi:10.1002/wrcr.20259, 2013.

Parameters:

  • grid (RasterModelGrid) – A grid.

  • method (required for 'MeasuredRadiationPT') – Priestley Taylor method will spit out radiation outputs too.

  • priestley_taylor_constant (float, optional) – Alpha used in Priestley Taylor method.

  • albedo (float, optional) – Albedo.

  • latent_heat_of_vaporization (float, optional) – Latent heat of vaporization for water Pwhv (Wd/(m*mm^2)).

  • psychometric_const (float, optional) – Psychometric constant (kPa (deg C)^-1).

  • stefan_boltzmann_const (float, optional) – Stefan Boltzmann’s constant (W/(m^2K^-4)).

  • solar_const (float, optional) – Solar constant (W/m^2).

  • latitude (float, optional) – Latitude (radians).

  • elevation_of_measurement (float, optional) – Elevation at which measurement was taken (m).

  • adjustment_coeff (float, optional) – adjustment coeff to predict Rs from air temperature (deg C)^-0.5.

  • lt (float, optional) – lag between peak TmaxF and solar forcing (days).

  • nd (float, optional) – Number of days in year (days).

  • MeanTmaxF (float, optional) – Mean annual rate of TmaxF (mm/d).

  • delta_d (float, optional) – Calibrated difference between max & min daily TmaxF (mm/d).

  • current_time (float, required only for 'Cosine' method) – Current time (Years)

  • const_potential_evapotranspiration (float, optional for) – ‘Constant’ method Constant PET value to be spatially distributed.

  • Tmin (float, required for 'Priestley Taylor' method) – Minimum temperature of the day (deg C)

  • Tmax (float, required for 'Priestley Taylor' method) – Maximum temperature of the day (deg C)

  • Tavg (float, required for 'Priestley Taylor' and 'MeasuredRadiationPT') – methods Average temperature of the day (deg C)

  • float (obs_radiation) – Observed radiation (W/m^2)

  • method – Observed radiation (W/m^2)

property Tavg

Average temperature of the day (deg C)

Tavg: float, required for ‘Priestley Taylor’ and ‘MeasuredRadiationPT’ methods.

property Tmax

Maximum temperature of the day (deg C)

Tmax: float, required for ‘Priestley Taylor’ method.

property Tmin

Minimum temperature of the day (deg C)

Tmin: float, required for ‘Priestley Taylor’ method.

__init__(grid, method='Cosine', priestley_taylor_const=1.26, albedo=0.6, latent_heat_of_vaporization=28.34, psychometric_const=0.066, stefan_boltzmann_const=5.67e-08, solar_const=1366.67, latitude=34.0, elevation_of_measurement=300, adjustment_coeff=0.18, lt=0.0, nd=365.0, MeanTmaxF=12.0, delta_d=5.0, current_time=None, const_potential_evapotranspiration=12.0, Tmin=0.0, Tmax=1.0, Tavg=0.5, obs_radiation=350.0)[source]
Parameters:

  • grid (RasterModelGrid) – A grid.

  • method (required for 'MeasuredRadiationPT') – Priestley Taylor method will spit out radiation outputs too.

  • priestley_taylor_constant (float, optional) – Alpha used in Priestley Taylor method.

  • albedo (float, optional) – Albedo.

  • latent_heat_of_vaporization (float, optional) – Latent heat of vaporization for water Pwhv (Wd/(m*mm^2)).

  • psychometric_const (float, optional) – Psychometric constant (kPa (deg C)^-1).

  • stefan_boltzmann_const (float, optional) – Stefan Boltzmann’s constant (W/(m^2K^-4)).

  • solar_const (float, optional) – Solar constant (W/m^2).

  • latitude (float, optional) – Latitude (radians).

  • elevation_of_measurement (float, optional) – Elevation at which measurement was taken (m).

  • adjustment_coeff (float, optional) – adjustment coeff to predict Rs from air temperature (deg C)^-0.5.

  • lt (float, optional) – lag between peak TmaxF and solar forcing (days).

  • nd (float, optional) – Number of days in year (days).

  • MeanTmaxF (float, optional) – Mean annual rate of TmaxF (mm/d).

  • delta_d (float, optional) – Calibrated difference between max & min daily TmaxF (mm/d).

  • current_time (float, required only for 'Cosine' method) – Current time (Years)

  • const_potential_evapotranspiration (float, optional for) – ‘Constant’ method Constant PET value to be spatially distributed.

  • Tmin (float, required for 'Priestley Taylor' method) – Minimum temperature of the day (deg C)

  • Tmax (float, required for 'Priestley Taylor' method) – Maximum temperature of the day (deg C)

  • Tavg (float, required for 'Priestley Taylor' and 'MeasuredRadiationPT') – methods Average temperature of the day (deg C)

  • float (obs_radiation) – Observed radiation (W/m^2)

  • method – Observed radiation (W/m^2)

static __new__(cls, *args, **kwds)
cite_as = ''
property const_potential_evapotranspiration

Constant PET value to be spatially distributed.

Used by ‘Constant’ method.

property coords

Return the coordinates of nodes on grid attached to the component.

property current_time

Current time.

Some components may keep track of the current time. In this case, the current_time attribute is incremented. Otherwise it is set to None.

Return type:

current_time

definitions = (('radiation__incoming_shortwave_flux', 'incident shortwave radiation'), ('radiation__net_flux', 'net radiation'), ('radiation__net_longwave_flux', 'net incident longwave radiation'), ('radiation__net_shortwave_flux', 'net incident shortwave radiation'), ('radiation__ratio_to_flat_surface', 'ratio of incident shortwave radiation on sloped surface to flat surface'), ('surface__potential_evapotranspiration_rate', 'potential sum of evaporation and potential transpiration'))
classmethod from_path(grid, path)

Create a component from an input file.

Parameters:

  • grid (ModelGrid) – A landlab grid.

  • path (str or file_like) – Path to a parameter file, contents of a parameter file, or a file-like object.

Returns:

A newly-created component.

Return type:

Component

property grid

Return the grid attached to the component.

initialize_optional_output_fields()

Create fields for a component based on its optional field outputs, if declared in _optional_var_names.

This method will create new fields (without overwrite) for any fields output by the component as optional. New fields are initialized to zero. New fields are created as arrays of floats, unless the component also contains the specifying property _var_type.

initialize_output_fields(values_per_element=None)

Create fields for a component based on its input and output var names.

This method will create new fields (without overwrite) for any fields output by, but not supplied to, the component. New fields are initialized to zero. Ignores optional fields. New fields are created as arrays of floats, unless the component specifies the variable type.

Parameters:

values_per_element (int (optional)) – On occasion, it is necessary to create a field that is of size (n_grid_elements, values_per_element) instead of the default size (n_grid_elements,). Use this keyword argument to acomplish this task.

input_var_names = ('radiation__ratio_to_flat_surface',)
name = 'PotentialEvapotranspiration'
property obs_radiation

Observed radiation (W/m^2)

obs_radiation float, required for ‘MeasuredRadiationPT’ method.

optional_var_names = ()
output_var_names = ('radiation__incoming_shortwave_flux', 'radiation__net_flux', 'radiation__net_longwave_flux', 'radiation__net_shortwave_flux', 'surface__potential_evapotranspiration_rate')
property shape

Return the grid shape attached to the component, if defined.

unit_agnostic = False
units = (('radiation__incoming_shortwave_flux', 'W/m^2'), ('radiation__net_flux', 'W/m^2'), ('radiation__net_longwave_flux', 'W/m^2'), ('radiation__net_shortwave_flux', 'W/m^2'), ('radiation__ratio_to_flat_surface', 'None'), ('surface__potential_evapotranspiration_rate', 'mm'))
update()[source]

Update fields with current conditions.

If the ‘Constant’ method is used, this method looks to the value of the const_potential_evapotranspiration property.

If the ‘PriestleyTaylor’ method is used, this method looks to the values of the Tmin, Tmax, and Tavg properties.

If the ‘MeasuredRadiationPT’ method is use this method looks to the values of the Tavg and obs_radiation property.

classmethod var_definition(name)

Get a description of a particular field.

Parameters:

name (str) – A field name.

Returns:

A description of each field.

Return type:

tuple of (name, *description*)

classmethod var_help(name)

Print a help message for a particular field.

Parameters:

name (str) – A field name.

classmethod var_loc(name)

Location where a particular variable is defined.

Parameters:

name (str) – A field name.

Returns:

The location (‘node’, ‘link’, etc.) where a variable is defined.

Return type:

str

var_mapping = (('radiation__incoming_shortwave_flux', 'cell'), ('radiation__net_flux', 'cell'), ('radiation__net_longwave_flux', 'cell'), ('radiation__net_shortwave_flux', 'cell'), ('radiation__ratio_to_flat_surface', 'cell'), ('surface__potential_evapotranspiration_rate', 'cell'))
classmethod var_type(name)

Returns the dtype of a field (float, int, bool, str…).

Parameters:

name (str) – A field name.

Returns:

The dtype of the field.

Return type:

dtype

classmethod var_units(name)

Get the units of a particular field.

Parameters:

name (str) – A field name.

Returns:

Units for the given field.

Return type:

str