Updated environment_mapping mechanism so that wind components can be …

…calculated from speed and either wind_from_direction or wind_to_direction. Added new test.

opendrift/models/basemodel.py

@@ -2502,7 +2502,7 @@ def run(self, time_step=None, steps=None, time_step_output=None,
                 self.add_metadata(keyword, self.fallback_values[var])
             else:
                 readers = self.priority_list[var]
-                if readers[0].startswith('constant_reader'):
+                if readers[0].startswith('constant_reader') and var in self.readers[readers[0]]._parameter_value_map:
                     self.add_metadata(keyword, self.readers[readers[
                                 0]]._parameter_value_map[var][0])
                 else:

opendrift/readers/basereader/variables.py

@@ -392,12 +392,16 @@ class Variables(ReaderDomain):
 
     environment_mappers = []
     environment_mappings = {
-        'wind_from_speed_and_direction': {
+        'wind_from_speed_and_direction_from': {
             'input': ['wind_speed', 'wind_from_direction'],
             'output': ['x_wind', 'y_wind'],
             'method':
-            lambda reader, var: reader.wind_from_speed_and_direction(var)
-        },
+            lambda reader, var: reader.wind_from_speed_and_direction(var)},
+        'wind_from_speed_and_direction_to': {
+            'input': ['wind_speed', 'wind_to_direction'],
+            'output': ['x_wind', 'y_wind'],
+            'method':
+            lambda reader, var: reader.wind_from_speed_and_direction(var)},
         'testvar': {
             'input': ['sea_ice_thickness'],
             'output': ['istjukkleik']
@@ -428,10 +432,12 @@ def set_buffer_size(self, max_speed, max_vertical_speed=None):
                          (self.buffer, self.name, max_speed))
 
     def wind_from_speed_and_direction(self, env):
-        north_wind = -env['wind_speed'] * np.cos(
-            np.radians(env['wind_from_direction']))
-        east_wind = -env['wind_speed'] * np.sin(
-            np.radians(env['wind_from_direction']))
+        if 'wind_from_direction' in env:
+            wfd = env['wind_from_direction']
+        else:
+            wfd = -env['wind_to_direction']
+        north_wind = -env['wind_speed']*np.cos(np.radians(wfd))
+        east_wind = -env['wind_speed']*np.sin(np.radians(wfd))
         env['x_wind'] = east_wind
         env['y_wind'] = north_wind
         # Rotating might be necessary generally

tests/readers/test_variables.py

@@ -1,7 +1,10 @@
 import numpy as np
 import pytest
 from . import *
+from datetime import datetime, timedelta
 from opendrift.readers import reader_netCDF_CF_generic
+from opendrift.readers import reader_constant
+from opendrift.models.oceandrift import OceanDrift
 
 
 def test_covers_positions(test_data):
@@ -19,4 +22,25 @@ def test_covers_positions(test_data):
     np.testing.assert_almost_equal(x_wind[0], 2.615, 2)
     np.testing.assert_almost_equal(x_wind[-1], -0.222, 2)
 
+def test_environment_mapping(test_data):
 
+    # Wind from NE
+    r = reader_constant.Reader({'wind_speed':5, 'wind_from_direction': 45,
+                                'land_binary_mask': 0})
+    o = OceanDrift(loglevel=50)
+    o.set_config('general:use_auto_landmask', False)
+    o.add_reader(r)
+    o.seed_elements(lon=4, lat=60, time=datetime.now())
+    o.run(steps=15)
+    np.testing.assert_almost_equal(o.elements.lon, 3.932, 3)
+    np.testing.assert_almost_equal(o.elements.lat, 59.966, 3)
+    # Wind from SW
+    r = reader_constant.Reader({'wind_speed':5, 'wind_from_direction': 225,
+                                'land_binary_mask': 0})
+    o = OceanDrift(loglevel=50)
+    o.set_config('general:use_auto_landmask', False)
+    o.add_reader(r)
+    o.seed_elements(lon=4, lat=60, time=datetime.now())
+    o.run(steps=15)
+    np.testing.assert_almost_equal(o.elements.lon, 4.068, 3)
+    np.testing.assert_almost_equal(o.elements.lat, 60.034, 3)