Roms chunk fix (#41)

* Add multiplier setting for vdatum to control transformation direction

* Start trying to fix roms rotation chunks

* More unified chunks

* cleanup

xreds/extensions/roms.py

@@ -40,6 +40,8 @@ def transform_dataset(self, ds: xr.Dataset, config: dict) -> xr.Dataset:
             )
             return ds
 
+        default_da = default_da.unify_chunks()
+
         # Start with u
         u_name = "u_sur" if "u_sur" in ds else "u"
         u = ds[u_name]
@@ -125,7 +127,17 @@ def transform_dataset(self, ds: xr.Dataset, config: dict) -> xr.Dataset:
         v_rotated.name = f"{v_name}_rotated"
         v_rotated.attrs["long_name"] = "v velocity rotated from ROMS grid"
 
-        ds[f"{u_name}_rotated"] = u_rotated
-        ds[f"{v_name}_rotated"] = v_rotated
+        ds[f"{u_name}_rotated"] = u_rotated.chunk(
+            dict(
+                xi_rho=default_da.chunksizes['xi_rho'],
+                eta_rho=default_da.chunksizes['eta_rho']
+            )
+        ).unify_chunks()
+        ds[f"{v_name}_rotated"] = v_rotated.chunk(
+            dict(
+                xi_rho=default_da.chunksizes['xi_rho'],
+                eta_rho=default_da.chunksizes['eta_rho']
+            )
+        ).unify_chunks()
 
         return ds