| Name | refet JSON |
| Version |
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| Summary | ASCE Standardized Reference Evapotranspiration Functions |
| upload_time | 2023-06-30 14:48:01 |
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| author | |
| requires_python | >=3.7 |
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===================================================
ASCE Standardized Reference Evapotranspiration (ET)
===================================================
|version| |build|
NumPy functions for computing daily and hourly reference ET following the ASCE Standardized Reference Evapotranspiration Equations (ASCE2005_).
Usage
=====
Daily Example
-------------
The following demonstrates how to compute a single daily ETr value using weather data for 2015-07-01 from the `Fallon, NV AgriMet station <https://www.usbr.gov/pn/agrimet/agrimetmap/falnda.html>`__.
The necessary unit conversions are shown on the input values.
The raw input data is available `here <https://www.usbr.gov/pn-bin/daily.pl?station=FALN&year=2015&month=7&day=1&year=2015&month=7&day=1&pcode=ETRS&pcode=MN&pcode=MX&pcode=SR&pcode=YM&pcode=UA>`__.
.. code-block:: console
import math
import refet
# The actual vapor pressure could be computed from the dew point temperature below
# or the tdew can be passed directly to the function
# Convert the dew point temperature to Celsius
# tdew = units._f2c(49.84)
# ea = 0.6108 * math.exp(17.27 * tdew / (tdew + 237.3))
# ea = refet.calcs._sat_vapor_pressure(tdew)
etr = refet.Daily(
tmin=66.65, tmax=102.80, tdew=49.84, rs=674.07, uz=4.80,
zw=3, elev=1208.5, lat=39.4575, doy=182, method='asce',
input_units={'tmin': 'F', 'tmax': 'F', 'tdew': 'F', 'rs': 'Langleys',
'uz': 'mph', 'lat': 'deg'}
).etr()
print(f'ETr: {float(etr):.2f} mm')
Hourly Example
--------------
The following demonstrates how to compute a single hourly ETr value using weather data for 18:00 UTC (11:00 AM PDT) on 2015-07-01 from the `Fallon, NV AgriMet station <https://www.usbr.gov/pn/agrimet/agrimetmap/falnda.html>`__.
The necessary unit conversions are shown on the input values.
The raw input data is available `here <https://www.usbr.gov/pn-bin/instant.pl?station=FALN&year=2015&month=7&day=1&year=2015&month=7&day=1&pcode=OB&pcode=EA&pcode=WS&pcode=SI&print_hourly=1>`__
.. code-block:: console
import refet
etr = refet.Hourly(
tmean=91.80, ea=1.20 , rs=61.16, uz=3.33, zw=3, elev=1208.5,
lat=39.4575, lon=-118.77388, doy=182, time=18, method='asce',
input_units={'tmean': 'F', 'rs': 'Langleys', 'uz': 'mph', 'lat': 'deg'}
).etr()
print(f'ETr: {float(etr):.2f} mm')
Input Parameters
================
Required Parameters (hourly & daily)
------------------------------------
======== ========== ====================================================
Variable Type Description [default units]
======== ========== ====================================================
uz ndarray Wind speed [m s-1]
zw float Wind speed height [m]
elev ndarray Elevation [m]
lat ndarray Latitude [degrees]
doy ndarray Day of year
======== ========== ====================================================
Required Ea Parameters (hourly & daily)
---------------------------------------------------
Either the "ea" or "tdew" parameter must be set
======== ========== ====================================================
Variable Type Description [default units]
======== ========== ====================================================
ea ndarray Actual vapor pressure [kPa]
tdew ndarray Dew point temperature [C]
======== ========== ====================================================
Required Daily Parameters
-------------------------
======== ========== ====================================================
Variable Type Description [default units]
======== ========== ====================================================
rs ndarray Incoming shortwave solar radiation [MJ m-2 d-1]
tmin ndarray Minimum daily temperature [C]
tmax ndarray Maximum daily temperature [C]
======== ========== ====================================================
Required Hourly Parameters
--------------------------
======== ========== ====================================================
Variable Type Description [default units]
======== ========== ====================================================
rs ndarray Incoming shortwave solar radiation [MJ m-2 h-1]
tmean ndarray Average hourly temperature [C]
lon ndarray Longitude [degrees]
time ndarray UTC hour at start of time period
======== ========== ====================================================
Optional Parameters
-------------------
=========== ========== ====================================================
Variable Type Description [default units]
=========== ========== ====================================================
method str | Calculation method
* 'asce' -- Calculations will follow ASCE-EWRI 2005 (default)
* 'refet' -- Calculations will follow RefET software
rso_type str | Override default clear sky solar radiation (Rso) calculation
| Defaults to None if not set
* 'full' -- Full clear sky solar formulation
* 'simple' -- Simplified clear sky solar formulation
* 'array' -- Read Rso values from "rso" function parameter
rso array_like | Clear sky solar radiation [MJ m-2 d-1 or MJ m-2 h-1]
* Only used if rso_type == 'array'
* Defaults to None if not set
input_units dict | Override default input unit types
| Input values will be converted to default unit types
=========== ========== ====================================================
Installation
============
The RefET python module can be installed with conda or pip:
.. code-block:: console
conda install refet
Issues
======
The functions have **not** been tested for inputs with different shapes/sizes and the broadcasting may not work correctly.
The user must handle the following:
+ File I/O
+ QA/QC of the input data
+ Filling missing or bad data
Cloudiness Fraction (hourly)
----------------------------
The cloudiness fraction (fcd) is computed as the ratio of the measured solar radiation (Rs) to the theoretical clear sky solar radiation (Rso). This ratio cannot be computed directly at night since Rso is 0. ASCE2005_ suggests computing a representative nighttime fcd based on the fcd at sunset and/or sunrise.
In the RefET module fcd is hard coded to 1 for all time steps with very low sun angles since the hourly reference ET is computed independently for each time step.
Calculation Method - ASCE vs. RefET
===================================
The main difference between the two "methods" is that the "asce" method attempts to follow the equations in ASCE2005_, whereas the "refet" method attempts to follow the calculations of the `RefET Software <https://www.uidaho.edu/cals/kimberly-research-and-extension-center/research/water-resources/ref-et-software>`__ as closely as possible. The difference in output between these methods is generally negligible (if not identical for realistic numbers of significant digits). Note that the default is set to "asce" to best match the calculations a user would expect to have happen. The "refet" method was added in order to help validate this code to the RefET Software.
Validation
==========
Please see the `validation document <VALIDATION.md>`__ for additional details on the source of the test values and the comparison of the functions to the Ref-ET software.
Dependencies
============
* `numpy <http://www.numpy.org>`__
Modules needed to run the test suite:
* `pandas <http://pandas.pydata.org>`__
* `pytest <https://docs.pytest.org/en/latest/>`__
* `pytz <http://pythonhosted.org/pytz/>`__
References
==========
.. _references:
.. [ASCE2005]
| ASCE-EWRI (2005). The ASCE standardized reference evapotranspiration equation.
| `https://ascelibrary.org/doi/book/10.1061/9780784408056 <https://ascelibrary.org/doi/book/10.1061/9780784408056>`__
.. |build| image:: https://github.com/WSWUP/refet/workflows/build/badge.svg
:alt: Build status
:target: https://github.com/WSWUP/refet
.. |version| image:: https://badge.fury.io/py/refet.svg
:alt: Latest version on PyPI
:target: https://badge.fury.io/py/refet
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"description": "===================================================\nASCE Standardized Reference Evapotranspiration (ET)\n===================================================\n\n|version| |build|\n\nNumPy functions for computing daily and hourly reference ET following the ASCE Standardized Reference Evapotranspiration Equations (ASCE2005_).\n\nUsage\n=====\n\nDaily Example\n-------------\n\nThe following demonstrates how to compute a single daily ETr value using weather data for 2015-07-01 from the `Fallon, NV AgriMet station <https://www.usbr.gov/pn/agrimet/agrimetmap/falnda.html>`__.\nThe necessary unit conversions are shown on the input values.\nThe raw input data is available `here <https://www.usbr.gov/pn-bin/daily.pl?station=FALN&year=2015&month=7&day=1&year=2015&month=7&day=1&pcode=ETRS&pcode=MN&pcode=MX&pcode=SR&pcode=YM&pcode=UA>`__.\n\n.. code-block:: console\n\n import math\n import refet\n\n # The actual vapor pressure could be computed from the dew point temperature below\n # or the tdew can be passed directly to the function\n # Convert the dew point temperature to Celsius\n # tdew = units._f2c(49.84)\n # ea = 0.6108 * math.exp(17.27 * tdew / (tdew + 237.3))\n # ea = refet.calcs._sat_vapor_pressure(tdew)\n\n etr = refet.Daily(\n tmin=66.65, tmax=102.80, tdew=49.84, rs=674.07, uz=4.80,\n zw=3, elev=1208.5, lat=39.4575, doy=182, method='asce',\n input_units={'tmin': 'F', 'tmax': 'F', 'tdew': 'F', 'rs': 'Langleys',\n 'uz': 'mph', 'lat': 'deg'}\n ).etr()\n\n print(f'ETr: {float(etr):.2f} mm')\n\nHourly Example\n--------------\n\nThe following demonstrates how to compute a single hourly ETr value using weather data for 18:00 UTC (11:00 AM PDT) on 2015-07-01 from the `Fallon, NV AgriMet station <https://www.usbr.gov/pn/agrimet/agrimetmap/falnda.html>`__.\nThe necessary unit conversions are shown on the input values.\nThe raw input data is available `here <https://www.usbr.gov/pn-bin/instant.pl?station=FALN&year=2015&month=7&day=1&year=2015&month=7&day=1&pcode=OB&pcode=EA&pcode=WS&pcode=SI&print_hourly=1>`__\n\n.. code-block:: console\n\n import refet\n\n etr = refet.Hourly(\n tmean=91.80, ea=1.20 , rs=61.16, uz=3.33, zw=3, elev=1208.5,\n lat=39.4575, lon=-118.77388, doy=182, time=18, method='asce',\n input_units={'tmean': 'F', 'rs': 'Langleys', 'uz': 'mph', 'lat': 'deg'}\n ).etr()\n\n print(f'ETr: {float(etr):.2f} mm')\n\n\nInput Parameters\n================\n\nRequired Parameters (hourly & daily)\n------------------------------------\n\n======== ========== ====================================================\nVariable Type Description [default units]\n======== ========== ====================================================\nuz ndarray Wind speed [m s-1]\nzw float Wind speed height [m]\nelev ndarray Elevation [m]\nlat ndarray Latitude [degrees]\ndoy ndarray Day of year\n======== ========== ====================================================\n\nRequired Ea Parameters (hourly & daily)\n---------------------------------------------------\n\nEither the \"ea\" or \"tdew\" parameter must be set\n\n======== ========== ====================================================\nVariable Type Description [default units]\n======== ========== ====================================================\nea ndarray Actual vapor pressure [kPa]\ntdew ndarray Dew point temperature [C]\n======== ========== ====================================================\n\nRequired Daily Parameters\n-------------------------\n\n======== ========== ====================================================\nVariable Type Description [default units]\n======== ========== ====================================================\nrs ndarray Incoming shortwave solar radiation [MJ m-2 d-1]\ntmin ndarray Minimum daily temperature [C]\ntmax ndarray Maximum daily temperature [C]\n======== ========== ====================================================\n\nRequired Hourly Parameters\n--------------------------\n\n======== ========== ====================================================\nVariable Type Description [default units]\n======== ========== ====================================================\nrs ndarray Incoming shortwave solar radiation [MJ m-2 h-1]\ntmean ndarray Average hourly temperature [C]\nlon ndarray Longitude [degrees]\ntime ndarray UTC hour at start of time period\n======== ========== ====================================================\n\nOptional Parameters\n-------------------\n\n=========== ========== ====================================================\nVariable Type Description [default units]\n=========== ========== ====================================================\nmethod str | Calculation method\n\n * 'asce' -- Calculations will follow ASCE-EWRI 2005 (default)\n * 'refet' -- Calculations will follow RefET software\n\nrso_type str | Override default clear sky solar radiation (Rso) calculation\n | Defaults to None if not set\n\n * 'full' -- Full clear sky solar formulation\n * 'simple' -- Simplified clear sky solar formulation\n * 'array' -- Read Rso values from \"rso\" function parameter\n\nrso array_like | Clear sky solar radiation [MJ m-2 d-1 or MJ m-2 h-1]\n\n * Only used if rso_type == 'array'\n * Defaults to None if not set\n\ninput_units dict | Override default input unit types\n | Input values will be converted to default unit types\n\n=========== ========== ====================================================\n\nInstallation\n============\n\nThe RefET python module can be installed with conda or pip:\n\n.. code-block:: console\n\n conda install refet\n\nIssues\n======\n\nThe functions have **not** been tested for inputs with different shapes/sizes and the broadcasting may not work correctly.\n\nThe user must handle the following:\n + File I/O\n + QA/QC of the input data\n + Filling missing or bad data\n\nCloudiness Fraction (hourly)\n----------------------------\n\nThe cloudiness fraction (fcd) is computed as the ratio of the measured solar radiation (Rs) to the theoretical clear sky solar radiation (Rso). This ratio cannot be computed directly at night since Rso is 0. ASCE2005_ suggests computing a representative nighttime fcd based on the fcd at sunset and/or sunrise.\n\nIn the RefET module fcd is hard coded to 1 for all time steps with very low sun angles since the hourly reference ET is computed independently for each time step.\n\nCalculation Method - ASCE vs. RefET\n===================================\n\nThe main difference between the two \"methods\" is that the \"asce\" method attempts to follow the equations in ASCE2005_, whereas the \"refet\" method attempts to follow the calculations of the `RefET Software <https://www.uidaho.edu/cals/kimberly-research-and-extension-center/research/water-resources/ref-et-software>`__ as closely as possible. The difference in output between these methods is generally negligible (if not identical for realistic numbers of significant digits). 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The ASCE standardized reference evapotranspiration equation.\n | `https://ascelibrary.org/doi/book/10.1061/9780784408056 <https://ascelibrary.org/doi/book/10.1061/9780784408056>`__\n\n.. |build| image:: https://github.com/WSWUP/refet/workflows/build/badge.svg\n :alt: Build status\n :target: https://github.com/WSWUP/refet\n.. |version| image:: https://badge.fury.io/py/refet.svg\n :alt: Latest version on PyPI\n :target: https://badge.fury.io/py/refet\n",
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