Conditions to match ref.time & hist.time, and also ref.time.size & sim.time.size

CHANGELOG.rst

@@ -20,6 +20,7 @@ Bug fixes
 Internal changes
 ^^^^^^^^^^^^^^^^
 * Changed french translations with word "pluvieux" to "avec précipitations". (:issue:`1960`, :pull:`1994`).
+* Using different time for `ref` and `hist` is now explicitly forbidden in many bias adjustment methods (e.g. `EmpiricalQuantileMapping`). (:issue:`1903`, :pull:`1995`)
 * `streamflow` entry replaced with `q` in ``variables.yml``.  (:issue:`1912`, :pull:`1996`)
 * In order to address 403 (forbidden) request errors when retrieving data from GitHub via ReadTheDocs, the ``nimbus`` class has been modified to use an overloaded `fetch` method that appends a User-Agent header to the request. (:pull:`2001`).
 * Addressed a very rare race condition that can happen if `pytest` is tearing down the test environment when running across multiple workers. (:pull:`1863`).

xclim/sdba/adjustment.py

@@ -77,6 +77,7 @@ class BaseAdjustment(ParametrizableWithDataset):
     """
 
     _allow_diff_calendars = True
+    _allow_diff_training_times = True
     _attribute = "_xclim_adjustment"
 
     def __init__(self, *args, _trained=False, **kwargs):
@@ -208,6 +209,12 @@ def __convert_units_to(_input_da, _internal_dim, _internal_target):
             convert_units_to(inda, target, context="infer") for inda in inputs
         ), target
 
+    @classmethod
+    def _check_matching_time(cls, ref, hist):
+        """Raise an error ref and hist times don't match."""
+        if all(ref.time == hist.time) is False:
+            raise ValueError("`ref` and `hist` should have the same time arrays.")
+
     @classmethod
     def _train(cls, ref, hist, **kwargs):
         raise NotImplementedError()
@@ -259,6 +266,9 @@ def train(cls, ref: DataArray, hist: DataArray, **kwargs) -> TrainAdjust:
         else:
             train_units = ""
 
+        if cls._allow_diff_training_times is False:
+            cls._check_matching_time(ref, hist)
+
         ds, params = cls._train(ref, hist, **kwargs)
         obj = cls(
             _trained=True,
@@ -340,6 +350,8 @@ class Adjust(BaseAdjustment):
     and returning the scen dataset/array.
     """
 
+    _replace_sim_time = True
+
     @classmethod
     def adjust(
         cls,
@@ -370,6 +382,13 @@ def adjust(
             sim = hist.copy()
             sim.attrs["_is_hist"] = True
 
+        # This below implies that ref.time and sim.time have the same size
+        # Since `ref,hist, sim` are in the same `map_groups` call, they must have
+        # the same time
+        if cls.__replace_sim_time:
+            sim_time = sim.time
+            sim["time"] = ref["time"]
+
         kwargs = parse_group(cls._adjust, kwargs)
         skip_checks = kwargs.pop("skip_input_checks", False)
 
@@ -385,6 +404,8 @@ def adjust(
             out = out.rename("scen").to_dataset()
 
         scen = out.scen
+        if cls.__replace_sim_time:
+            scen["time"] = sim_time
 
         params = ", ".join([f"{k}={repr(v)}" for k, v in kwargs.items()])
         infostr = f"{cls.__name__}.adjust(ref, hist, sim, {params})"
@@ -442,7 +463,7 @@ class EmpiricalQuantileMapping(TrainAdjust):
     :cite:cts:`sdba-deque_frequency_2007`
     """
 
-    _allow_diff_calendars = False
+    _allow_diff_training_times = False
 
     @classmethod
     def _train(
@@ -542,7 +563,7 @@ class DetrendedQuantileMapping(TrainAdjust):
 
     """
 
-    _allow_diff_calendars = False
+    _allow_diff_training_times = False
 
     @classmethod
     def _train(
@@ -869,7 +890,7 @@ class LOCI(TrainAdjust):
     :cite:cts:`sdba-schmidli_downscaling_2006`
     """
 
-    _allow_diff_calendars = False
+    _allow_diff_training_times = False
 
     @classmethod
     def _train(
@@ -921,7 +942,7 @@ class Scaling(TrainAdjust):
         The interpolation method to use then interpolating the adjustment factors. Defaults to "nearest".
     """
 
-    _allow_diff_calendars = False
+    _allow_diff_training_times = False
 
     @classmethod
     def _train(
@@ -1738,6 +1759,8 @@ class MBCn(TrainAdjust):
     Only  "time" and "time.dayofyear" (with a suitable window) are implemented as possible values for `group`.
     """
 
+    _allow_diff_training_times = False
+
     @classmethod
     def _train(
         cls,