Make sure sh cannot be set without nh

oggm/cfg.py

@@ -28,7 +28,7 @@
 except ImportError:
     pass
 
-from oggm.exceptions import InvalidParamsError
+from oggm.exceptions import InvalidParamsError, InvalidWorkflowError
 
 # Local logger
 log = logging.getLogger(__name__)
@@ -114,6 +114,7 @@ class ParamsLoggingDict(ResettingOrderedDict):
 
     def __setitem__(self, key, value):
         # Overrides the original dic to log the change
+        self._check_input(key, value)
         if self.do_log:
             self._log_param_change(key, value)
         ResettingOrderedDict.__setitem__(self, key, value)
@@ -159,6 +160,15 @@ def _log_param_change(self, key, value):
                                                                       prev,
                                                                       value))
 
+    def _check_input(self, key, value):
+
+        if key == 'hydro_month_sh' and value == 1:
+            nh = self.get('hydro_month_nh')
+            if nh is not None and nh != 1:
+                msg = ("When setting PARAMS['hydro_month_sh'] to 1, please set "
+                       "PARAMS['hydro_month_nh'] to 1 first.")
+                raise InvalidWorkflowError(msg)
+
 
 # Globals
 IS_INITIALIZED = False

oggm/core/climate.py

@@ -1416,6 +1416,13 @@ def mu_star_calibration_from_geodetic_mb(gdir,
         max_mu_star = cfg.PARAMS['max_mu_star']
 
     sm = cfg.PARAMS['hydro_month_' + gdir.hemisphere]
+    if sm == 1:
+        # Check that the other hemisphere is set to 1 as well to avoid surprises
+        oh = 'sh' if gdir.hemisphere == 'nh' else 'nh'
+        if cfg.PARAMS['hydro_month_' + oh] != 1:
+            raise InvalidParamsError('Please set both hydro_month_nh and '
+                                     'hydro_month_sh to 1 for geodetic '
+                                     'calibration.')
     if sm != 1 and not ignore_hydro_months:
         raise InvalidParamsError('mu_star_calibration_from_geodetic_mb makes '
                                  'more sense when applied on calendar years '

oggm/tests/test_utils.py

@@ -26,6 +26,7 @@
                               characs_apply_func)
 from oggm.utils import shape_factor_adhikari
 from oggm.exceptions import (InvalidParamsError, InvalidDEMError,
+                             InvalidWorkflowError,
                              DownloadVerificationFailedException)
 
 
@@ -393,6 +394,12 @@ def test_defaults(self):
         else:
             self.assertFalse(cfg.PATHS['working_dir'])
 
+    def test_params_warn(self):
+        with pytest.raises(InvalidWorkflowError):
+            cfg.PARAMS['hydro_month_sh'] = 1
+        cfg.PARAMS['hydro_month_nh'] = 1
+        cfg.PARAMS['hydro_month_sh'] = 1
+
     def test_pathsetter(self):
         cfg.PATHS['working_dir'] = os.path.join('~', 'my_OGGM_wd')
         expected = os.path.join(self.homedir, 'my_OGGM_wd')