negate *and* reindex depth in ds before fieldset creation

Author: j-atkins

src/virtualship/instruments/base.py

@@ -120,7 +120,7 @@ def simulate(
 
     def execute(self, measurements: list, out_path: str | Path) -> None:
         """Run instrument simulation."""
-        TMP = False  # TODO: just for dev; remove before merging
+        TMP = True  # TODO: just for dev; remove before merging
         instrument_name = self.__class__.__name__.split("Instrument")[0]
 
         if not self.verbose_progress:
@@ -220,6 +220,10 @@ def _generate_fieldset(self) -> parcels.FieldSet:
             # TODO: I think this is potentially slowing down simulations slightly... compared to v0.3 anyway for *drifters*
             ds.load()  # TODO: tmp step during v4 alpha stage... probably to be updated on the Parcels end
 
+            # negate depth and reindex (to suit Parcels XGrid strictly increasing depth convention)
+            ds["depth"] = -ds["depth"]
+            ds = ds.reindex(depth=ds["depth"][::-1])  #
+
             fields = {key: ds[field_var_name]}
             ds_fset = parcels.convert.copernicusmarine_to_sgrid(fields=fields)
             fs = parcels.FieldSet.from_sgrid_conventions(ds_fset)