Metadata-Version: 2.1
Name: openet-refet-gee
Version: 0.6.3
Summary: Google Earth Engine based ASCE Standardized Reference Evapotranspiration Functions
Author-email: Charles Morton <charles.morton@dri.edu>
License:                                  Apache License
                                   Version 2.0, January 2004
                                http://www.apache.org/licenses/
        
           TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
        
           1. Definitions.
        
              "License" shall mean the terms and conditions for use, reproduction,
              and distribution as defined by Sections 1 through 9 of this document.
        
              "Licensor" shall mean the copyright owner or entity authorized by
              the copyright owner that is granting the License.
        
              "Legal Entity" shall mean the union of the acting entity and all
              other entities that control, are controlled by, or are under common
              control with that entity. For the purposes of this definition,
              "control" means (i) the power, direct or indirect, to cause the
              direction or management of such entity, whether by contract or
              otherwise, or (ii) ownership of fifty percent (50%) or more of the
              outstanding shares, or (iii) beneficial ownership of such entity.
        
              "You" (or "Your") shall mean an individual or Legal Entity
              exercising permissions granted by this License.
        
              "Source" form shall mean the preferred form for making modifications,
              including but not limited to software source code, documentation
              source, and configuration files.
        
              "Object" form shall mean any form resulting from mechanical
              transformation or translation of a Source form, including but
              not limited to compiled object code, generated documentation,
              and conversions to other media types.
        
              "Work" shall mean the work of authorship, whether in Source or
              Object form, made available under the License, as indicated by a
              copyright notice that is included in or attached to the work
              (an example is provided in the Appendix below).
        
              "Derivative Works" shall mean any work, whether in Source or Object
              form, that is based on (or derived from) the Work and for which the
              editorial revisions, annotations, elaborations, or other modifications
              represent, as a whole, an original work of authorship. For the purposes
              of this License, Derivative Works shall not include works that remain
              separable from, or merely link (or bind by name) to the interfaces of,
              the Work and Derivative Works thereof.
        
              "Contribution" shall mean any work of authorship, including
              the original version of the Work and any modifications or additions
              to that Work or Derivative Works thereof, that is intentionally
              submitted to Licensor for inclusion in the Work by the copyright owner
              or by an individual or Legal Entity authorized to submit on behalf of
              the copyright owner. For the purposes of this definition, "submitted"
              means any form of electronic, verbal, or written communication sent
              to the Licensor or its representatives, including but not limited to
              communication on electronic mailing lists, source code control systems,
              and issue tracking systems that are managed by, or on behalf of, the
              Licensor for the purpose of discussing and improving the Work, but
              excluding communication that is conspicuously marked or otherwise
              designated in writing by the copyright owner as "Not a Contribution."
        
              "Contributor" shall mean Licensor and any individual or Legal Entity
              on behalf of whom a Contribution has been received by Licensor and
              subsequently incorporated within the Work.
        
           2. Grant of Copyright License. Subject to the terms and conditions of
              this License, each Contributor hereby grants to You a perpetual,
              worldwide, non-exclusive, no-charge, royalty-free, irrevocable
              copyright license to reproduce, prepare Derivative Works of,
              publicly display, publicly perform, sublicense, and distribute the
              Work and such Derivative Works in Source or Object form.
        
           3. Grant of Patent License. Subject to the terms and conditions of
              this License, each Contributor hereby grants to You a perpetual,
              worldwide, non-exclusive, no-charge, royalty-free, irrevocable
              (except as stated in this section) patent license to make, have made,
              use, offer to sell, sell, import, and otherwise transfer the Work,
              where such license applies only to those patent claims licensable
              by such Contributor that are necessarily infringed by their
              Contribution(s) alone or by combination of their Contribution(s)
              with the Work to which such Contribution(s) was submitted. If You
              institute patent litigation against any entity (including a
              cross-claim or counterclaim in a lawsuit) alleging that the Work
              or a Contribution incorporated within the Work constitutes direct
              or contributory patent infringement, then any patent licenses
              granted to You under this License for that Work shall terminate
              as of the date such litigation is filed.
        
           4. Redistribution. You may reproduce and distribute copies of the
              Work or Derivative Works thereof in any medium, with or without
              modifications, and in Source or Object form, provided that You
              meet the following conditions:
        
              (a) You must give any other recipients of the Work or
                  Derivative Works a copy of this License; and
        
              (b) You must cause any modified files to carry prominent notices
                  stating that You changed the files; and
        
              (c) You must retain, in the Source form of any Derivative Works
                  that You distribute, all copyright, patent, trademark, and
                  attribution notices from the Source form of the Work,
                  excluding those notices that do not pertain to any part of
                  the Derivative Works; and
        
              (d) If the Work includes a "NOTICE" text file as part of its
                  distribution, then any Derivative Works that You distribute must
                  include a readable copy of the attribution notices contained
                  within such NOTICE file, excluding those notices that do not
                  pertain to any part of the Derivative Works, in at least one
                  of the following places: within a NOTICE text file distributed
                  as part of the Derivative Works; within the Source form or
                  documentation, if provided along with the Derivative Works; or,
                  within a display generated by the Derivative Works, if and
                  wherever such third-party notices normally appear. The contents
                  of the NOTICE file are for informational purposes only and
                  do not modify the License. You may add Your own attribution
                  notices within Derivative Works that You distribute, alongside
                  or as an addendum to the NOTICE text from the Work, provided
                  that such additional attribution notices cannot be construed
                  as modifying the License.
        
              You may add Your own copyright statement to Your modifications and
              may provide additional or different license terms and conditions
              for use, reproduction, or distribution of Your modifications, or
              for any such Derivative Works as a whole, provided Your use,
              reproduction, and distribution of the Work otherwise complies with
              the conditions stated in this License.
        
           5. Submission of Contributions. Unless You explicitly state otherwise,
              any Contribution intentionally submitted for inclusion in the Work
              by You to the Licensor shall be under the terms and conditions of
              this License, without any additional terms or conditions.
              Notwithstanding the above, nothing herein shall supersede or modify
              the terms of any separate license agreement you may have executed
              with Licensor regarding such Contributions.
        
           6. Trademarks. This License does not grant permission to use the trade
              names, trademarks, service marks, or product names of the Licensor,
              except as required for reasonable and customary use in describing the
              origin of the Work and reproducing the content of the NOTICE file.
        
           7. Disclaimer of Warranty. Unless required by applicable law or
              agreed to in writing, Licensor provides the Work (and each
              Contributor provides its Contributions) on an "AS IS" BASIS,
              WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
              implied, including, without limitation, any warranties or conditions
              of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
              PARTICULAR PURPOSE. You are solely responsible for determining the
              appropriateness of using or redistributing the Work and assume any
              risks associated with Your exercise of permissions under this License.
        
           8. Limitation of Liability. In no event and under no legal theory,
              whether in tort (including negligence), contract, or otherwise,
              unless required by applicable law (such as deliberate and grossly
              negligent acts) or agreed to in writing, shall any Contributor be
              liable to You for damages, including any direct, indirect, special,
              incidental, or consequential damages of any character arising as a
              result of this License or out of the use or inability to use the
              Work (including but not limited to damages for loss of goodwill,
              work stoppage, computer failure or malfunction, or any and all
              other commercial damages or losses), even if such Contributor
              has been advised of the possibility of such damages.
        
           9. Accepting Warranty or Additional Liability. While redistributing
              the Work or Derivative Works thereof, You may choose to offer,
              and charge a fee for, acceptance of support, warranty, indemnity,
              or other liability obligations and/or rights consistent with this
              License. However, in accepting such obligations, You may act only
              on Your own behalf and on Your sole responsibility, not on behalf
              of any other Contributor, and only if You agree to indemnify,
              defend, and hold each Contributor harmless for any liability
              incurred by, or claims asserted against, such Contributor by reason
              of your accepting any such warranty or additional liability.
        
           END OF TERMS AND CONDITIONS
        
           APPENDIX: How to apply the Apache License to your work.
        
              To apply the Apache License to your work, attach the following
              boilerplate notice, with the fields enclosed by brackets "[]"
              replaced with your own identifying information. (Don't include
              the brackets!)  The text should be enclosed in the appropriate
              comment syntax for the file format. We also recommend that a
              file or class name and description of purpose be included on the
              same "printed page" as the copyright notice for easier
              identification within third-party archives.
        
           Copyright [yyyy] [name of copyright owner]
        
           Licensed under the Apache License, Version 2.0 (the "License");
           you may not use this file except in compliance with the License.
           You may obtain a copy of the License at
        
               http://www.apache.org/licenses/LICENSE-2.0
        
           Unless required by applicable law or agreed to in writing, software
           distributed under the License is distributed on an "AS IS" BASIS,
           WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
           See the License for the specific language governing permissions and
           limitations under the License.
        
Project-URL: Homepage, https://github.com/Open-ET/openet-refet-gee
Keywords: RefET,OpenET,Earth Engine,evapotranspiration
Classifier: Programming Language :: Python :: 3
Classifier: License :: OSI Approved :: Apache Software License
Classifier: Operating System :: OS Independent
Requires-Python: >=3.8
Description-Content-Type: text/x-rst
License-File: LICENSE.txt
Requires-Dist: earthengine-api>=0.1.364
Provides-Extra: test
Requires-Dist: pytest; extra == "test"
Requires-Dist: pandas; extra == "test"
Requires-Dist: pytz; extra == "test"

================================================================================
OpenET - Google Earth Engine ASCE Standardized Reference Evapotranspiration (ET)
================================================================================

|version| |build|

This repository provides `Google Earth Engine <https://earthengine.google.com/>`__ Python API based implementation of the ASCE Standardized Reference Evapotranspiration Equations (ASCE2005_) for computing daily and hourly reference ET.

Usage
=====

Daily
-----

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 ee
    import openet.refetgee

    # Unit conversions
    tmin_c = (66.65 - 32) * (5.0 / 9)                          # F -> C
    tmax_c = (102.80 - 32) * (5.0 / 9)                         # F -> C
    tdew_c = (57.26 - 32) * (5.0 / 9)                          # F -> C
    ea = 0.6108 * math.exp(17.27 * tdew_c / (tdew_c + 237.3))  # kPa
    rs = (674.07 * 0.041868)                                   # Langleys -> MJ m-2 d-1
    uz = 4.80 * 0.44704                                        # mpg -> m s-1
    lat = 39.4575                                              # degrees

    etr = openet.refetgee.Daily(
        tmin=tmin_c, tmax=tmax_c, ea=ea, rs=rs, uz=uz, zw=3, elev=1208.5,
        lat=lat, doy=182).etr.getInfo()

    print('ETr: {:.2f} mm'.format(float(etr)))

Hourly
------

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 math
    import ee
    import openet.refetgee

    # Unit conversions
    tmean_c = (91.80 - 32) * (5.0 / 9)           # F -> C
    ea = 1.20                                    # kPa
    rs = (61.16 * 0.041868)                      # Langleys -> MJ m-2 h-1
    uz = 3.33 * 0.44704                          # mph -> m s-1
    lat = 39.4575                                # degrees
    lon = -118.77388                             # degrees

    etr = openet.refetgee.Hourly(
        tmean=tmean_c, ea=ea, rs=rs, uz=uz, zw=3, elev=1208.5,
        lat=lat, lon=lon, doy=182, time=18).etr.getInfo()

    print('ETr: {:.2f} mm'.format(float(etr)))

GRIDMET
-------

A helper function for computing daily ETo and ETr for `GRIDMET <http://www.climatologylab.org/gridmet.html>`__ images is available.

.. code-block:: console

    import ee
    import openet.refetgee

    source_img = ee.Image(ee.ImageCollection('IDAHO_EPSCOR/GRIDMET').first())
    etr = openet.refetgee.Daily.gridmet(source_img).etr\
        .reduceRegion(reducer=ee.Reducer.first(),
                      geometry=ee.Geometry.Point(-118.77388, 39.4575),
                      scale=1000)\
        .getInfo()

    print('ETr: {:.2f} mm'.format(float(etr['etr'])))

NLDAS
-----

Helper functions for computing daily/hourly ETo/ETr for `NLDAS <https://ldas.gsfc.nasa.gov/nldas/NLDAS2forcing.php>`__ images are available.

For the daily function, the NLDAS collection must be filtered to a single 24 hour period.

.. code-block:: console

    import ee
    import openet.refetgee

    source_coll = ee.ImageCollection('NASA/NLDAS/FORA0125_H002')\
        .filterDate('2015-07-01', '2015-07-02')
    etr = openet.refetgee.Daily.nldas(source_coll).etr\
        .reduceRegion(reducer=ee.Reducer.first(),
                      geometry=ee.Geometry.Point(-118.77388, 39.4575),
                      scale=1000)\
        .getInfo()

    print('ETr: {:.2f} mm'.format(float(etr['etr'])))

.. code-block:: console

    import ee
    import openet.refetgee

    source_img = ee.Image('NASA/NLDAS/FORA0125_H002/A20150701_2000')
    etr = openet.refetgee.Hourly.nldas(source_img).etr\
        .reduceRegion(reducer=ee.Reducer.first(),
                      geometry=ee.Geometry.Point(-118.77388, 39.4575),
                      scale=1000)\
        .getInfo()

    print('ETr: {:.2f} mm'.format(float(etr['etr'])))

CFSv2
-----

A helper function for computing daily ETo and ETr for `CFSv2 <http://>`__ images is available.

For the daily function, the CFSv2 collection must be filtered to a single 24 hour period.

.. code-block:: console

    import ee
    import openet.refetgee

    source_coll = ee.ImageCollection('NOAA/CFSV2/FOR6H')\
        .filterDate('2015-07-01', '2015-07-02')
    etr = openet.refetgee.Daily.cfsv2(source_coll).etr\
        .reduceRegion(reducer=ee.Reducer.first(),
                      geometry=ee.Geometry.Point(-118.77388, 39.4575),
                      scale=1000)\
        .getInfo()

    print('ETr: {:.2f} mm'.format(float(etr['etr'])))

RTMA
-----

Helper functions for computing daily/hourly ETo/ETr for `RTMA <https://>`__ images are available.

For the daily function, the RTMA collection must be filtered to a single 24 hour period.

.. code-block:: console

    import ee
    import openet.refetgee

    source_coll = ee.ImageCollection('NOAA/NWS/RTMA')\
        .filterDate('2015-07-01', '2015-07-02')
    etr = openet.refetgee.Daily.rtma(source_coll).etr\
        .reduceRegion(reducer=ee.Reducer.first(),
                      geometry=ee.Geometry.Point(-118.77388, 39.4575),
                      scale=1000)\
        .getInfo()

    print('ETr: {:.2f} mm'.format(float(etr['etr'])))

.. code-block:: console

    import ee
    import openet.refetgee

    source_img = ee.Image('NOAA/NWS/RTMA/2015070120')
    etr = openet.refetgee.Hourly.nldas(source_img).etr\
        .reduceRegion(reducer=ee.Reducer.first(),
                      geometry=ee.Geometry.Point(-118.77388, 39.4575),
                      scale=1000)\
        .getInfo()

    print('ETr: {:.2f} mm'.format(float(etr['etr'])))

ERA5-Land
---------

Helper functions for computing daily/hourly ETo/ETr for `ERA5-Land <https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-land>`__ images are available.

For the daily function, the ERA5-Land collection must be filtered to a single 24 hour period.

.. code-block:: console

    import ee
    import openet.refetgee

    source_coll = ee.ImageCollection('ECMWF/ERA5_LAND/HOURLY')\
        .filterDate('2015-07-01', '2015-07-02')
    etr = openet.refetgee.Daily.era5_land(source_coll).etr\
        .reduceRegion(reducer=ee.Reducer.first(),
                      geometry=ee.Geometry.Point(-118.77388, 39.4575),
                      scale=1000)\
        .getInfo()

    print('ETr: {:.2f} mm'.format(float(etr['etr'])))

.. code-block:: console

    import ee
    import openet.refetgee

    source_img = ee.Image('ECMWF/ERA5_LAND/HOURLY/20150701T20')
    etr = openet.refetgee.Hourly.era5_land(source_img).etr\
        .reduceRegion(reducer=ee.Reducer.first(),
                      geometry=ee.Geometry.Point(-118.77388, 39.4575),
                      scale=1000)\
        .getInfo()

    print('ETr: {:.2f} mm'.format(float(etr['etr'])))

Input Parameters
================

Required Parameters (hourly & daily)
------------------------------------

========  ===================  =================================================
Variable  Type                 Description [units]
========  ===================  =================================================
ea        ee.Image             Actual vapor pressure [kPa]
rs        ee.Image             Incoming shortwave solar radiation [MJ m-2 day-1]
uz        ee.Image             Wind speed [m s-1]
zw        ee.Number            Wind speed height [m]
elev      ee.Image, ee.Number  Elevation [m]
lat       ee.Image, ee.Number  Latitude [degrees]
doy       ee.Image, ee.Number  Day of year
========  ===================  =================================================

Required Daily Parameters
-------------------------

========  ===================  =================================================
Variable  Type                 Description [units]
========  ===================  =================================================
tmin      ee.Image             Minimum daily temperature [C]
tmax      ee.Image             Maximum daily temperature [C]
========  ===================  =================================================

Required Hourly Parameters
--------------------------

========  ===================  =================================================
Variable  Type                 Description [units]
========  ===================  =================================================
tmean     ee.Image             Average hourly temperature [C]
lon       ee.Image, ee.Number  Longitude [degrees]
time      ee.Number            UTC hour at start of time period
========  ===================  =================================================

Optional Parameters
-------------------

========  ===================  ====================================================
Variable  Type                 Description [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 (default)
                               * 'simple' -- Simplified clear sky solar formulation (Eq. 19)
                               * 'array' -- Read Rso values from "rso" function parameter

rso       ee.Image, ee.Number  | Clear sky solar radiation [MJ m-2 day-1]

                               * Only needed if rso_type is 'array'
                               * Defaults to None if not set

========  ===================  ====================================================

Issues
======

Currently the user must handle all of the file I/O and unit conversions.

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.  ASCE-EWRI 2005 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.

Installation
============

The OpenET RefET GEE python module can be installed via pip:

.. code-block:: console

    pip install openet-refet-gee

OpenET Namespace Package
========================

Each OpenET model is stored in the "openet" folder (namespace).  The model can then be imported as a "dot" submodule of the main openet module.

.. code-block:: console

    import openet.refetgee as refetgee

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
============

 * `earthengine-api <https://github.com/google/earthengine-api>`__

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
==========

.. [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/Open-ET/openet-refet-gee/workflows/build/badge.svg
   :alt: Build status
   :target: https://github.com/Open-ET/openet-refet-gee
.. |version| image:: https://badge.fury.io/py/openet-refet-gee.svg
   :alt: Latest version on PyPI
   :target: https://badge.fury.io/py/openet-refet-gee
