add mask

aifs/data/lsm.grib

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:6660ca07729fd8f2ac3fb8bfeee66e7513a355ca90d287f39b5987832c44a891
+size 1627680

aifs/initial_conditions.py

@@ -228,7 +228,7 @@ def _build_fields(ekd, ekr, date: datetime.datetime, source: str = SOURCE):
             if var in fields:
                 fields[var][:, ocean_mask] = np.nan
     except Exception:
-        pass  # lsm.grib not found; skip masking
+        pass
 
     # Convert geopotential height → geopotential  (Z = gh × g)
     G = 9.80665