Improve variable alias managament (#595)

Add support for several variables that have different names in CMP5 and CMIP6

doc/recipe/overview.rst

@@ -317,6 +317,19 @@ define the ``start_year`` and ``end_year`` items in the variable section,
 because the diagnostic script assumes that all the data has the same time
 range.
 
+Variable short names usually do not change between datasets supported by
+ESMValCore, as they are usually changed to match CMIP. Nevertheless, there are
+small changes in variable names in CMIP6 with respect to CMIP5 (i.e. sea ice
+concentration changed from ``sic`` to ``siconc``). ESMValCore is aware of some
+of them and can do the automatic translation when needed. It will even do the
+translation in the preprocessed file so the diagnostic does not have to deal
+with this complexity, setting the short name in all files to match the one used
+by the recipe. For example, if ``sic`` is requested, ESMValTool will
+find ``sic`` or ``siconc`` depending on the project, but all preprocessed files
+while use ``sic`` as their short_name. If the recipe requested ``siconc``, the
+preprocessed files will be identical except that they will use the short_name
+``siconc`` instead.
+
 Diagnostic and variable specific datasets
 -----------------------------------------
 The ``additional_datasets`` option can be used to add datasets beyond those

esmvalcore/_data_finder.py

@@ -219,10 +219,12 @@ def _get_filenames_glob(variable, drs):
 
 
 def _find_input_files(variable, rootpath, drs):
+    short_name = variable['short_name']
+    variable['short_name'] = variable['original_short_name']
     input_dirs = _find_input_dirs(variable, rootpath, drs)
     filenames_glob = _get_filenames_glob(variable, drs)
     files = find_files(input_dirs, filenames_glob)
-
+    variable['short_name'] = short_name
     return (files, input_dirs, filenames_glob)
 
 

esmvalcore/_recipe.py

@@ -109,7 +109,7 @@ def _add_cmor_info(variable, override=False):
         raise RecipeError(
             f"Unable to load CMOR table (project) '{project}' for variable "
             f"'{short_name}' with mip '{mip}'")
-
+    variable['original_short_name'] = table_entry.short_name
     for key in cmor_keys:
         if key not in variable or override:
             value = getattr(table_entry, key, None)
@@ -348,6 +348,8 @@ def _get_default_settings(variable, config_user, derive=False):
 
     # Configure saving cubes to file
     settings['save'] = {'compress': config_user['compress_netcdf']}
+    if variable['short_name'] != variable['original_short_name']:
+        settings['save']['alias'] = variable['short_name']
 
     return settings