From d0649d936c6edbdcaecbbc19daedd06c0ffb5469 Mon Sep 17 00:00:00 2001
From: Dennis Yatunin <dyatun@gmail.com>
Date: Wed, 19 Feb 2025 11:23:17 -0800
Subject: [PATCH] Fix bug in DSS of level Fields (#2193)

---
 NEWS.md                 | 3 +++
 src/Grids/extruded.jl   | 5 +++--
 src/Grids/level.jl      | 8 ++++----
 test/Spaces/unit_dss.jl | 5 ++++-
 4 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 271d41d792..d2cfc92f51 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -4,6 +4,9 @@ ClimaCore.jl Release Notes
 main
 -------
 
+ - Fixed bug in DSS for level fields. PR [2194](https://github.com/CliMA/ClimaCore.jl/pull/2194).
+   Closed [2193](https://github.com/CliMA/ClimaCore.jl/issues/2193).
+
 v0.14.25
 -------
 
diff --git a/src/Grids/extruded.jl b/src/Grids/extruded.jl
index 6c583cad47..7c8baa50c8 100644
--- a/src/Grids/extruded.jl
+++ b/src/Grids/extruded.jl
@@ -131,8 +131,9 @@ vertical_topology(grid::ExtrudedFiniteDifferenceGrid) =
 
 # Since ∂z/∂ξ₃ and r are continuous across element boundaries, we can reuse
 # the horizontal weights instead of calling compute_dss_weights on the
-# extruded local geometry.
-dss_weights(grid::AbstractExtrudedFiniteDifferenceGrid, ::Staggering) =
+# extruded local geometry. If we ever need to use extruded weights, this method
+# will need to distinguish between weights on centers and weights on faces.
+dss_weights(grid::AbstractExtrudedFiniteDifferenceGrid, _) =
     dss_weights(grid.horizontal_grid, nothing)
 
 local_geometry_data(grid::AbstractExtrudedFiniteDifferenceGrid, ::CellCenter) =
diff --git a/src/Grids/level.jl b/src/Grids/level.jl
index bb18b0d0ea..6f84e4a6b2 100644
--- a/src/Grids/level.jl
+++ b/src/Grids/level.jl
@@ -16,10 +16,10 @@ level(
 
 topology(levelgrid::LevelGrid) = topology(levelgrid.full_grid)
 
-dss_weights(levelgrid::LevelGrid{<:Any, Int}, ::Nothing) =
-    level(dss_weights(levelgrid.full_grid, CellCenter()), levelgrid.level)
-dss_weights(levelgrid::LevelGrid{<:Any, PlusHalf{Int}}, ::Nothing) =
-    level(dss_weights(levelgrid.full_grid, CellFace()), levelgrid.level + half)
+# The DSS weights for extruded spaces are currently the same as the weights for
+# horizontal spaces. If we ever need to use extruded weights, this method will
+# need to extract the weights at a particular level.
+dss_weights(levelgrid::LevelGrid, _) = dss_weights(levelgrid.full_grid, nothing)
 
 local_geometry_type(::Type{LevelGrid{G, L}}) where {G, L} =
     local_geometry_type(G)
diff --git a/test/Spaces/unit_dss.jl b/test/Spaces/unit_dss.jl
index bdf6f8e4e4..c079433776 100644
--- a/test/Spaces/unit_dss.jl
+++ b/test/Spaces/unit_dss.jl
@@ -138,7 +138,10 @@ end
             space_kwargs = (; context, topography, deep, autodiff_metric)
             center_space =
                 TU.CenterExtrudedFiniteDifferenceSpace(FT; space_kwargs...)
-            for space in (center_space, Spaces.face_space(center_space))
+            face_space = Spaces.face_space(center_space)
+            level_space1 = Spaces.level(center_space, 2)
+            level_space2 = Spaces.level(face_space, 1 + Spaces.half)
+            for space in (center_space, face_space, level_space1, level_space2)
                 test_dss_conservation(space)
             end
         end