Merge pull request #6 from Open-ET/era5

ERA5-Land

.gitignore

@@ -4,6 +4,7 @@ __pycache__/
 *$py.class
 
 # Distribution / packaging
+build/
 dist/
 .eggs/
 *.egg-info/

README.rst

@@ -177,6 +177,42 @@ For the daily function, the RTMA collection must be filtered to a single 24 hour
 
     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
 ================
 

openet/refetgee/__init__.py

@@ -1,4 +1,4 @@
 from .daily import Daily
 from .hourly import Hourly
 
-__version__ = '0.5.2'
+__version__ = '0.6.0'

openet/refetgee/daily.py

@@ -770,6 +770,83 @@ def rtma(cls, input_coll, rs=None, zw=None, elev=None, lat=None,
             rso_type=rso_type,
         )
 
+    @classmethod
+    def era5_land(cls, input_coll, zw=None, elev=None, lat=None,
+                  method='asce', rso_type=None):
+        """Initialize daily RefET from a hourly ERA5-Land image collection
+
+        Parameters
+        ----------
+        input_coll : ee.ImageCollection
+            Collection of ERA5-Land hourly images for a single day from the
+            collection ECMWF/ERA5_LAND/HOURLY.
+        zw : ee.Number, optional
+            Wind speed height [m] (the default is 10).
+        elev : ee.Image or ee.Number, optional
+            Elevation image [m].  The OpenET ERA5-Land elevation image
+            (projects/openet/assets/meteorology/era5land/elevation)
+            will be used if not set.
+        lat : ee.Image or ee.Number
+            Latitude image [degrees].  The OpenET ERA5-Land latitude image
+            (projects/openet/assets/meteorology/era5land/latitude)
+            will be used if not set.
+        method : {'asce' (default), 'refet'}, optional
+            Specifies which calculation method to use.
+            * 'asce' -- Calculations will follow ASCE-EWRI 2005.
+            * 'refet' -- Calculations will follow RefET software.
+        rso_type : {None (default), 'full' , 'simple'}, optional
+            Specifies which clear sky solar radiation (Rso) model to use.
+            * None -- Rso type will be determined from "method" parameter
+            * 'full' -- Full clear sky solar formulation
+            * 'simple' -- Simplified clear sky solar formulation
+
+        Notes
+        -----
+        Temperatures are converted from K to C.
+        Solar radiation is converted from J m-2 to MJ m-2 day-1.
+        Actual vapor pressure is computed from dew point temperature.
+
+        """
+        input_coll = ee.ImageCollection(input_coll)
+        start_date = ee.Date(ee.Image(input_coll.first()).get('system:time_start'))
+
+        if zw is None:
+            zw = ee.Number(10)
+        if elev is None:
+            elev = ee.Image('projects/openet/assets/meteorology/era5land/elevation')\
+                .rename(['elevation'])
+        if lat is None:
+            lat = ee.Image('projects/openet/assets/meteorology/era5land/latitude')\
+            # lat = ee.Image('projects/openet/assets/meteorology/era5land/elevation')\
+            #     .multiply(0).add(ee.Image.pixelLonLat().select('latitude'))\
+            #     .rename(['latitude'])
+
+        def wind_magnitude(input_img):
+            """Compute hourly wind magnitude from vectors"""
+            return ee.Image(input_img.select(['u_component_of_wind_10m'])).pow(2)\
+                .add(ee.Image(input_img.select(['v_component_of_wind_10m'])).pow(2))\
+                .sqrt().rename(['wind_10m'])
+
+        wind_img = ee.Image(ee.ImageCollection(input_coll.map(wind_magnitude)).mean())
+
+        return cls(
+            tmax=input_coll.select(['temperature_2m']).max().subtract(273.15),
+            tmin=input_coll.select(['temperature_2m']).min().subtract(273.15),
+            ea=calcs._sat_vapor_pressure(
+                input_coll.select(['dewpoint_temperature_2m']).mean().subtract(273.15)
+            ),
+            # TODO: Check that solar does not need additional conversion
+            rs=input_coll.select(['surface_solar_radiation_downwards_hourly'])
+                .sum().divide(1000000),
+            uz=wind_img,
+            zw=zw,
+            elev=elev,
+            lat=lat,
+            doy=ee.Number(start_date.getRelative('day', 'year')).add(1).double(),
+            method=method,
+            rso_type=rso_type,
+        )
+
     # @classmethod
     # def prism(cls, input_img, lat=None):
     #     """Initialize daily RefET from a PRISM image

openet/refetgee/hourly.py

@@ -400,3 +400,76 @@ def rtma(cls, input_img, rs=None, zw=None, elev=None, lat=None, lon=None,
             time=ee.Number(start_date.get('hour')),
             method=method,
         )
+
+    @classmethod
+    def era5_land(cls, input_img, zw=None, elev=None, lat=None, lon=None,
+                  method='asce'):
+        """Initialize hourly RefET from an ERA5-Land image
+
+        Parameters
+        ----------
+        input_img : ee.Image
+            ERA5-Land hourly image from the collection ECMWF/ERA5_LAND/HOURLY.
+        zw : ee.Number, optional
+            Wind speed height [m] (the default is 10).
+        elev : ee.Image or ee.Number, optional
+            Elevation image [m].  The OpenET ERA5-Land elevation image
+            (projects/openet/assets/meteorology/era5land/elevation)
+            will be used if not set.
+        lat : ee.Image or ee.Number
+            Latitude image [degrees].  The OpenET ERA5-Land latitude image
+            (projects/openet/assets/meteorology/era5land/latitude)
+            will be used if not set.
+        lon : ee.Image or ee.Number
+            Longitude image [degrees].  The OpenET ERA5-Land longitude image
+            (projects/openet/assets/meteorology/era5land/longitude)
+            will be used if not set.
+        method : {'asce' (default), 'refet'}, optional
+            Specifies which calculation method to use.
+            * 'asce' -- Calculations will follow ASCE-EWRI 2005.
+            * 'refet' -- Calculations will follow RefET software.
+
+        Notes
+        -----
+        Temperatures are converted from K to C.
+        Solar radiation is converted from J m-2 to MJ m-2 day-1.
+        Actual vapor pressure is computed from dew point temperature.
+
+        """
+        start_date = ee.Date(input_img.get('system:time_start'))
+
+        if zw is None:
+            zw = ee.Number(10)
+        if elev is None:
+            elev = ee.Image('projects/openet/assets/meteorology/era5land/elevation')\
+                .rename(['elevation'])
+        if lat is None:
+            lat = ee.Image('projects/openet/assets/meteorology/era5land/latitude')
+            # lat = ee.Image('projects/openet/assets/meteorology/era5land/elevation')\
+            #     .multiply(0).add(ee.Image.pixelLonLat().select('latitude'))\
+            #     .rename(['latitude'])
+        if lon is None:
+            lon = ee.Image('projects/openet/assets/meteorology/era5land/longitude')
+            # lon = ee.Image('projects/openet/assets/meteorology/era5land/elevation')\
+            #     .multiply(0).add(ee.Image.pixelLonLat().select('longitude'))\
+            #     .rename(['longitude'])
+
+        return cls(
+            tmean=input_img.select(['temperature_2m']).subtract(273.15),
+            ea=calcs._sat_vapor_pressure(
+                input_img.select(['dewpoint_temperature_2m']).subtract(273.15)
+            ),
+            rs=input_img.select(['surface_solar_radiation_downwards_hourly'])
+                .divide(1000000),
+            uz=input_img.select(['u_component_of_wind_10m']).pow(2)
+                .add(input_img.select(['v_component_of_wind_10m']).pow(2))
+                .sqrt().rename(['wind_10m']),
+            zw=zw,
+            elev=elev,
+            lat=lat,
+            lon=lon,
+            doy=ee.Number(start_date.getRelative('day', 'year')).add(1).double(),
+            # time=ee.Number(start_date.getRelative('hour', 'day')),
+            time=ee.Number(start_date.get('hour')),
+            method=method,
+        )