diff --git a/CHANGELOG.md b/CHANGELOG.md
index fe66d2136..f00c0114d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Add `AGENTS.md` file to the repo to give agents more information about the codebase and the contribution culture.[\#416](https://github.com/mllam/neural-lam/pull/416) @sadamov
 
+- Support global domains with no boundary mask: `boundary_mask` can now return `None`, and the model and visualisation code handles this gracefully [\#444](https://github.com/mllam/neural-lam/pull/444) @RajdeepKushwaha5
+
 - Enable `pin_memory` in DataLoaders when GPU is available for faster async CPU-to-GPU data transfers [\#236](https://github.com/mllam/neural-lam/pull/236) @abhaygoudannavar
 
 ### Changed
diff --git a/neural_lam/datastore/base.py b/neural_lam/datastore/base.py
index f6dddb007..854c05b15 100644
--- a/neural_lam/datastore/base.py
+++ b/neural_lam/datastore/base.py
@@ -274,17 +274,20 @@ def get_dataarray(
 
     @cached_property
     @abc.abstractmethod
-    def boundary_mask(self) -> xr.DataArray:
+    def boundary_mask(self) -> Optional[xr.DataArray]:
         """
         Return the boundary mask for the dataset, with spatial dimensions
         stacked. Where the value is 1, the grid point is a boundary point, and
         where the value is 0, the grid point is not a boundary point.
 
+        For global datastores that have no lateral boundaries, this should
+        return None.
+
         Returns
         -------
-        xr.DataArray
+        xr.DataArray or None
             The boundary mask for the dataset, with dimensions
-            `('grid_index',)`.
+            `('grid_index',)`, or None for global domains.
 
         """
         pass
diff --git a/neural_lam/models/ar_model.py b/neural_lam/models/ar_model.py
index a411a3afc..bd3131321 100644
--- a/neural_lam/models/ar_model.py
+++ b/neural_lam/models/ar_model.py
@@ -124,11 +124,17 @@ def __init__(
         # Instantiate loss function
         self.loss = metrics.get_metric(args.loss)
 
-        boundary_mask = torch.tensor(
-            da_boundary_mask.values, dtype=torch.float32
-        ).unsqueeze(
-            1
-        )  # add feature dim
+        if da_boundary_mask is not None:
+            boundary_mask = torch.tensor(
+                da_boundary_mask.values, dtype=torch.float32
+            ).unsqueeze(
+                1
+            )  # add feature dim
+        else:
+            # Global domain: no boundary points, all grid points are interior
+            boundary_mask = torch.zeros(
+                self.num_grid_nodes, 1, dtype=torch.float32
+            )
 
         self.register_buffer("boundary_mask", boundary_mask, persistent=False)
         # Pre-compute interior mask for use in loss function
diff --git a/neural_lam/vis.py b/neural_lam/vis.py
index 06f2f6d35..01c544c42 100644
--- a/neural_lam/vis.py
+++ b/neural_lam/vis.py
@@ -108,7 +108,7 @@ def plot_on_axis(
         shading="auto",
     )
 
-    if boundary_alpha is not None:
+    if boundary_alpha is not None and datastore.boundary_mask is not None:
         # Overlay boundary mask
         mask_da = datastore.boundary_mask
         mask_values = mask_da.values
@@ -128,7 +128,7 @@ def plot_on_axis(
             shading="auto",
         )
 
-    if crop_to_interior:
+    if crop_to_interior and datastore.boundary_mask is not None:
         # Calculate extent of interior
         mask_da = datastore.boundary_mask
         mask_values = mask_da.values
diff --git a/tests/conftest.py b/tests/conftest.py
index 47237ed55..c3f6a1445 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -16,7 +16,7 @@
 )
 
 # Local
-from .dummy_datastore import DummyDatastore
+from .dummy_datastore import DummyDatastore, GlobalDummyDatastore
 
 # Disable weights and biases to avoid unnecessary logging
 # and to avoid having to deal with authentication
@@ -103,9 +103,11 @@ def download_meps_example_reduced_dataset():
     ),
     npyfilesmeps=None,
     dummydata=None,
+    dummydata_global=None,
 )
 
 DATASTORES[DummyDatastore.SHORT_NAME] = DummyDatastore
+DATASTORES[GlobalDummyDatastore.SHORT_NAME] = GlobalDummyDatastore
 
 
 def init_datastore_example(datastore_kind):
diff --git a/tests/dummy_datastore.py b/tests/dummy_datastore.py
index 3a844d6d9..16446afa5 100644
--- a/tests/dummy_datastore.py
+++ b/tests/dummy_datastore.py
@@ -758,3 +758,26 @@ def num_grid_points(self) -> int:
     @property
     def state_feature_weights_values(self) -> list[float]:
         return [1.0]
+
+
+class GlobalDummyDatastore(DummyDatastore):
+    """
+    Variant of DummyDatastore that simulates a global domain with no
+    lateral boundaries. A global setup should not have a boundary mask
+    at all, so ``boundary_mask`` returns None.
+    """
+
+    SHORT_NAME = "dummydata_global"
+
+    @cached_property
+    def boundary_mask(self) -> None:
+        """Return None for global domains (no boundary mask).
+
+        A global domain has no lateral boundaries, so no boundary mask
+        is needed. The model will use predictions everywhere.
+
+        Returns
+        -------
+        None
+        """
+        return None
diff --git a/tests/test_datastores.py b/tests/test_datastores.py
index 4ce3875ea..7a9c063b1 100644
--- a/tests/test_datastores.py
+++ b/tests/test_datastores.py
@@ -225,16 +225,22 @@ def test_get_dataarray(datastore_name):
 @pytest.mark.parametrize("datastore_name", DATASTORES.keys())
 def test_boundary_mask(datastore_name):
     """Check that the `datastore.boundary_mask` property is implemented and
-    that the returned object is an xarray DataArray with the correct shape."""
+    that the returned object is an xarray DataArray with the correct shape,
+    or None for global domains."""
     datastore = init_datastore_example(datastore_name)
     da_mask = datastore.boundary_mask
 
+    if da_mask is None:
+        # Global-style datastore: no boundary mask at all
+        return
+
     assert isinstance(da_mask, xr.DataArray)
     assert set(da_mask.dims) == {"grid_index"}
     assert da_mask.dtype == "int"
     assert set(da_mask.values) == {0, 1}
-    assert da_mask.sum() > 0
-    assert da_mask.sum() < da_mask.size
+    # If a mask is present it must have both boundary and interior points
+    mask_sum = int(da_mask.sum())
+    assert 0 < mask_sum < da_mask.size
 
     if isinstance(datastore, BaseRegularGridDatastore):
         grid_shape = datastore.grid_shape_state
diff --git a/tests/test_training.py b/tests/test_training.py
index 972740695..cc54b82cb 100644
--- a/tests/test_training.py
+++ b/tests/test_training.py
@@ -189,3 +189,16 @@ def all_gather(self, tensor, sync_grads=False):
         "all_gather_cat produced incorrectly ordered/combined values "
         "on multi-device simulation"
     )
+
+
+def test_training_global():
+    """Test global-style datastore boundary behavior (no boundary mask).
+    Training with this datastore is already exercised via the parametrized
+    test_training, so this test only verifies the global boundary mask
+    property to avoid duplicate expensive training runs."""
+    datastore = init_datastore_example("dummydata_global")
+
+    # Verify the global property: boundary mask should be None
+    assert (
+        datastore.boundary_mask is None
+    ), "GlobalDummyDatastore boundary_mask should be None for global domains"