regrid 2D data onto 2D space with LatLongZPoints

Author: juliasloan25

NEWS.md

@@ -4,6 +4,12 @@ ClimaUtilities.jl Release Notes
 main
 ------
 
+#### Allow regridding 2D data onto 2D spaces with LatLongZ coordinates. PR[#176](https://github.com/CliMA/ClimaUtilities.jl/pull/176)
+
+Some 2D spaces use `LatLongPoint` coordinates and others use `LatLongZPoint`,
+depending on how they were constructed. Both cases are now supported, so we can
+read in 2D data onto a 2D space with either coordinate type.
+
 #### Interpolation method for InterpolationsRegridder
 
 `InterpolationsRegridder` now accepts the new keyword argument
@@ -29,9 +35,9 @@ v0.1.23
 
 #### Support for Box Interpolations Regridder. PR[#151](https://github.com/CliMA/ClimaUtilities.jl/pull/151)
 
-`Regridders.IterpolationsRegridder` now supports regridding on 
-`ClimaCore.Geometry.XYZPoint` objects which allows for interpolation 
-onto boxes and single column simulations. 
+`Regridders.IterpolationsRegridder` now supports regridding on
+`ClimaCore.Geometry.XYZPoint` objects which allows for interpolation
+onto boxes and single column simulations.
 
 v0.1.22
 ------

ext/InterpolationsRegridderExt.jl

@@ -111,6 +111,23 @@ This function is allocating.
 """
 function Regridders.regrid(regridder::InterpolationsRegridder, data, dimensions)
     FT = ClimaCore.Spaces.undertype(regridder.target_space)
+
+    # For a 2D space with LatLongZ coordinates, we need to drop the z dimension to regrid 2D data.
+    if eltype(regridder.coordinates) <: ClimaCore.Geometry.LatLongZPoint &&
+       !(
+           regridder.target_space isa
+           ClimaCore.Spaces.ExtrudedFiniteDifferenceSpace
+       ) &&
+       length(dimensions) == 2
+
+        @warn "Regridding 2D data onto a 2D space with LatLongZ coordinates."
+        coords = map(regridder.coordinates) do coord
+            ClimaCore.Geometry.LatLongPoint(coord.lat, coord.long)
+        end
+    else
+        coords = regridder.coordinates
+    end
+
     dimensions_FT = map(dimensions, regridder.dim_increasing) do dim, increasing
         !increasing ? reverse(FT.(dim)) : FT.(dim)
     end
@@ -135,7 +152,7 @@ function Regridders.regrid(regridder::InterpolationsRegridder, data, dimensions)
     # Move it to GPU (if needed)
     gpuitp = Adapt.adapt(ClimaComms.array_type(regridder.target_space), itp)
 
-    return map(regridder.coordinates) do coord
+    return map(coords) do coord
         gpuitp(totuple(coord)...)
     end
 end

test/regridders.jl

@@ -205,27 +205,29 @@ end
 
         coordinates = ClimaCore.Fields.coordinate_field(horzspace)
 
+        # Since lon uses periodic BCs but is not periodic itself, error is large at 180 degrees.
+        # We check that the error is small at other indices, and that the values at -180 and 180 agree.
+        function check_lon_error(coords_lon, lon_regrid)
+            inds_normal = findall(!=(180), Array(parent(coords_lon)))
+            err_lon = abs.(
+                Array(parent(coords_lon))[inds_normal] .-
+                Array(parent(lon_regrid))[inds_normal],
+            )
+            @test maximum(err_lon) < 1e-4
+
+            inds_lon_180 = findall(==(180), Array(parent(coords_lon)))
+            inds_lon_neg180 = findall(==(-180), Array(parent(coords_lon)))
+            err_lon_180 = abs.(
+                Array(parent(lon_regrid))[inds_lon_180] .-
+                Array(parent(coords_lon))[inds_lon_neg180],
+            )
+            @test maximum(err_lon_180) < 1e-5
+        end
+
         # Compute max err
         err_lat = abs.(coordinates.lat .- regridded_lat)
         @test maximum(err_lat) < 1e-5
-
-        # Since lon uses periodic BCs, error is large at 180 degrees.
-        # We check that the error is small at other indices, and that the values at -180 and 180 agree.
-        # Note that for data that is actually periodic, the error at 180 degrees will also be small.
-        inds_normal = findall(!=(180), parent(coordinates.long))
-        err_lon = abs.(
-            parent(coordinates.long)[inds_normal] .-
-            parent(regridded_lon)[inds_normal],
-        )
-        @test maximum(err_lon) < 1e-4
-
-        inds_lon_180 = findall(==(180), parent(coordinates.long))
-        inds_lon_neg180 = findall(==(-180), parent(coordinates.long))
-        err_lon_180 = abs.(
-            parent(regridded_lon)[inds_lon_180] .-
-            parent(coordinates.long)[inds_lon_neg180],
-        )
-        @test maximum(err_lon_180) < 1e-5
+        check_lon_error(coordinates.long, regridded_lon)
 
         # 3D space
         extrapolation_bc = (
@@ -273,28 +275,47 @@ end
 
         # Compute max err
         err_lat = abs.(coordinates.lat .- regridded_lat)
-        err_lon = abs.(coordinates.long .- regridded_lon)
         err_z = abs.(coordinates.z .- regridded_z)
 
         @test maximum(err_lat) < 1e-5
         @test maximum(err_z) < 1e-5
+        check_lon_error(coordinates.long, regridded_lon)
 
-        # Since lon uses periodic BCs but is not periodic itself, error is large at 180 degrees.
-        # We check that the error is small at other indices, and that the values at -180 and 180 agree.
-        inds_normal = findall(!=(180), parent(coordinates.long))
-        err_lon = abs.(
-            parent(coordinates.long)[inds_normal] .-
-            parent(regridded_lon)[inds_normal],
+        # 2D space with LatLongZ coordinates
+        surface_space = ClimaCore.Spaces.level(hv_center_space, 1) # SpectralElementSpace2D with LatLongZPoint coordinates
+        coordinates = ClimaCore.Fields.coordinate_field(surface_space)
+        @assert !(
+            surface_space isa ClimaCore.Spaces.ExtrudedFiniteDifferenceSpace
         )
-        @test maximum(err_lon) < 1e-4
+        @assert eltype(coordinates) <: ClimaCore.Geometry.LatLongZPoint
 
-        inds_lon_180 = findall(==(180), parent(coordinates.long))
-        inds_lon_neg180 = findall(==(-180), parent(coordinates.long))
-        err_lon_180 = abs.(
-            parent(regridded_lon)[inds_lon_180] .-
-            parent(coordinates.long)[inds_lon_neg180],
-        )
-        @test maximum(err_lon_180) < 1e-5
+        # 3D data
+        reg_2d = Regridders.InterpolationsRegridder(surface_space)
+
+        regridded_lat_3d = Regridders.regrid(reg_2d, data_lat3D, dimensions3D)
+        regridded_lon_3d = Regridders.regrid(reg_2d, data_lon3D, dimensions3D)
+
+        # Compute max err
+        err_lat = abs.(coordinates.lat .- regridded_lat_3d)
+        @test maximum(err_lat) < 1e-5
+        check_lon_error(coordinates.long, regridded_lon_3d)
+
+        # 2D data
+        @test_logs (
+            :warn,
+            "Regridding 2D data onto a 2D space with LatLongZ coordinates.",
+        ) Regridders.regrid(reg_2d, data_lat2D, dimensions2D)
+        @test_logs (
+            :warn,
+            "Regridding 2D data onto a 2D space with LatLongZ coordinates.",
+        ) Regridders.regrid(reg_2d, data_lon2D, dimensions2D)
+
+        regridded_lat_2d = Regridders.regrid(reg_2d, data_lat2D, dimensions2D)
+        regridded_lon_2d = Regridders.regrid(reg_2d, data_lon2D, dimensions2D)
+
+        err_lat = abs.(coordinates.lat .- regridded_lat_2d)
+        @test maximum(err_lat) < 1e-5
+        check_lon_error(coordinates.long, regridded_lon_2d)
     end
 end