From b39300799c3038fcbb512af80cf9b351c655d463 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 30 Apr 2026 12:25:51 +0100
Subject: [PATCH 01/17] Adds a global model application for CURV

Fixes #2089
---
 src/CSET/operators/curvature.py | 99 +++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 src/CSET/operators/curvature.py

diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
new file mode 100644
index 000000000..24ae37de2
--- /dev/null
+++ b/src/CSET/operators/curvature.py
@@ -0,0 +1,99 @@
+# © Crown copyright, Met Office (2022-2026) and CSET contributors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""A module containing different implementations of CURV.
+
+The diagnostics here are separate implementations of CURV for both
+global models and limited-area models.
+"""
+
+import numpy as np
+
+
+def lat_lon_identifier(original_lat, original_lon, distance, bearing):
+    """Find the latitude and longitude of new points based on great circle distance."""
+    R = 6371.0
+    lat_rad = np.radians(original_lat)
+    lon_rad = np.radians(original_lon)
+    bearing_rad = np.radians(bearing)
+
+    new_lat = np.arcsin(
+        np.sin(lat_rad) * np.cos(distance / R)
+        + np.cos(lat_rad) * np.sin(distance / R) * np.cos(bearing_rad)
+    )
+    new_lon = lon_rad + np.arctan2(
+        np.sin(bearing_rad) * np.sin(distance / R) * np.cos(lat_rad),
+        np.cos(distance / R) - np.sin(lat_rad) * np.sin(new_lat),
+    )
+
+    new_lon = np.where(new_lon > 180.0, new_lon - 360.0, new_lon)
+
+    return new_lat, new_lon
+
+
+# def curvature_function(central, surrounding, tolerance, radial_points):
+#    """Calculate the intermediate data for CURV diagnostic."""
+#    shape_of_surrounding = surrounding.shape
+#    binary_difference = np.zeros(shape_of_surrounding)
+#    for rp in range(radial_points):
+#        binary_difference[:, rp] = np.where(
+#            surrounding[:, rp] < central[:] + tolerance, 1, 0
+#        )
+#        binary_difference[:, rp] = np.where(
+#            surroudnig[:, rp] > central[:] - tolerance, -1, binary_difference[:, rp]
+#        )
+#    curvature = bindary_difference.sum(axis=1)
+#    return curvature
+
+
+# def curv(
+#    radius, num_radial_points, north, south, east, west, tolerance, cube, outputfile
+# ):
+#    """Calculate the CURV diagnostic."""
+#    if (num_radial_points != 8) or (num_radial_points != 16):
+#        raise ValueError(
+#            f"Number of radial points should be 8 or 16. You have provided {num_radial_points}."
+#        )
+#    else:
+#        bearing = np.linspace(0.0, 360.0, num_radial_points + 1)
+#
+#    data_area = [north, west, south, east]
+#
+#    logging.info(
+#        f"CURV calculated base on {num_radial_points} radial points, a {radius} km radius, with {tolerance} tolerance."
+#    )
+#    logging.info(f"CURV calculated over area {data_area}.")
+#
+#    extracted_data = cube.extract(lon)
+#    extract_lats = extract_data.extract(lat)
+#
+#    points = np.size(extract_data.core_data())
+#
+#    curv = np.zeros(points)
+#
+#    new_lats = np.zeros((points, num_radial_points))
+#    new_lons = np.zeros((points, num_radial_points))
+#
+#    new_vals = np.zeros((points, num_radial_points))
+#
+#    for i in range(num_radial_points):
+#        new_lats[:, i], new_lons[:, i] = lat_lon_identifier(
+#            lats, lons, radius, bearing[i]
+#        )
+#
+#        new_vals[:, i] = cube.interpolate(new_lats[:, i], new_lons[:, i])
+#
+#    curv = curvature_function(cube, new_vals, tolerance, num_radial_points)
+#
+#    return curv

From 2e85ea50404bedfd4b13bfaaafff1fec8791ebcf Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 30 Apr 2026 12:30:16 +0100
Subject: [PATCH 02/17] Adds operators into CSET operators init and
 documentation

---
 docs/source/reference/operators.rst | 9 +++++++++
 src/CSET/operators/__init__.py      | 2 ++
 2 files changed, 11 insertions(+)

diff --git a/docs/source/reference/operators.rst b/docs/source/reference/operators.rst
index db6ab6aa1..a2da92d35 100644
--- a/docs/source/reference/operators.rst
+++ b/docs/source/reference/operators.rst
@@ -86,6 +86,15 @@ CSET.operators.convection
 .. automodule:: CSET.operators.convection
    :members:
 
+Curvature Operators
+~~~~~~~~~~~~~~~~~~~
+
+CSET.operators.curvature
+------------------------
+
+.. automodule:: CSET.operators.curvature
+   :members:
+
 Ensemble Operators
 ~~~~~~~~~~~~~~~~~~
 
diff --git a/src/CSET/operators/__init__.py b/src/CSET/operators/__init__.py
index cf583c30d..b8ab7812e 100644
--- a/src/CSET/operators/__init__.py
+++ b/src/CSET/operators/__init__.py
@@ -32,6 +32,7 @@
     collapse,
     constraints,
     convection,
+    curvature,
     ensembles,
     filters,
     humidity,
@@ -56,6 +57,7 @@
     "collapse",
     "constraints",
     "convection",
+    "curvature",
     "ensembles",
     "execute_recipe",
     "filters",

From f86b5d9f2089b68a6ccee2d46412733d464ea683 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 30 Apr 2026 16:02:22 +0100
Subject: [PATCH 03/17] Near full version of a slow CURV operator

---
 src/CSET/operators/curvature.py | 113 ++++++++++++++++----------------
 1 file changed, 55 insertions(+), 58 deletions(-)

diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
index 24ae37de2..4fd7511a1 100644
--- a/src/CSET/operators/curvature.py
+++ b/src/CSET/operators/curvature.py
@@ -18,12 +18,15 @@
 global models and limited-area models.
 """
 
+import logging
+
+import iris
 import numpy as np
 
 
-def lat_lon_identifier(original_lat, original_lon, distance, bearing):
+def _lat_lon_identifier(original_lat, original_lon, distance, bearing):
     """Find the latitude and longitude of new points based on great circle distance."""
-    R = 6371.0
+    R = 6371.0  # km.
     lat_rad = np.radians(original_lat)
     lon_rad = np.radians(original_lon)
     bearing_rad = np.radians(bearing)
@@ -37,63 +40,57 @@ def lat_lon_identifier(original_lat, original_lon, distance, bearing):
         np.cos(distance / R) - np.sin(lat_rad) * np.sin(new_lat),
     )
 
-    new_lon = np.where(new_lon > 180.0, new_lon - 360.0, new_lon)
+    new_lat = np.degrees(new_lat)
+    new_lon = np.degrees(new_lon)
+    new_lon = np.where(new_lon > 360.0, new_lon - 360.0, new_lon)
 
     return new_lat, new_lon
 
 
-# def curvature_function(central, surrounding, tolerance, radial_points):
-#    """Calculate the intermediate data for CURV diagnostic."""
-#    shape_of_surrounding = surrounding.shape
-#    binary_difference = np.zeros(shape_of_surrounding)
-#    for rp in range(radial_points):
-#        binary_difference[:, rp] = np.where(
-#            surrounding[:, rp] < central[:] + tolerance, 1, 0
-#        )
-#        binary_difference[:, rp] = np.where(
-#            surroudnig[:, rp] > central[:] - tolerance, -1, binary_difference[:, rp]
-#        )
-#    curvature = bindary_difference.sum(axis=1)
-#    return curvature
-
-
-# def curv(
-#    radius, num_radial_points, north, south, east, west, tolerance, cube, outputfile
-# ):
-#    """Calculate the CURV diagnostic."""
-#    if (num_radial_points != 8) or (num_radial_points != 16):
-#        raise ValueError(
-#            f"Number of radial points should be 8 or 16. You have provided {num_radial_points}."
-#        )
-#    else:
-#        bearing = np.linspace(0.0, 360.0, num_radial_points + 1)
-#
-#    data_area = [north, west, south, east]
-#
-#    logging.info(
-#        f"CURV calculated base on {num_radial_points} radial points, a {radius} km radius, with {tolerance} tolerance."
-#    )
-#    logging.info(f"CURV calculated over area {data_area}.")
-#
-#    extracted_data = cube.extract(lon)
-#    extract_lats = extract_data.extract(lat)
-#
-#    points = np.size(extract_data.core_data())
-#
-#    curv = np.zeros(points)
-#
-#    new_lats = np.zeros((points, num_radial_points))
-#    new_lons = np.zeros((points, num_radial_points))
-#
-#    new_vals = np.zeros((points, num_radial_points))
-#
-#    for i in range(num_radial_points):
-#        new_lats[:, i], new_lons[:, i] = lat_lon_identifier(
-#            lats, lons, radius, bearing[i]
-#        )
-#
-#        new_vals[:, i] = cube.interpolate(new_lats[:, i], new_lons[:, i])
-#
-#    curv = curvature_function(cube, new_vals, tolerance, num_radial_points)
-#
-#    return curv
+def curv(central, radius, num_radial_points=16, tol=0):
+    """Calculate the CURV diagnostic."""
+    if (num_radial_points == 8) or (num_radial_points == 16):
+        bearing = np.linspace(0.0, 360.0, num_radial_points + 1)[:-1]
+    else:
+        raise ValueError(
+            f"Number of radial points should be 8 or 16. You have provided {num_radial_points}."
+        )
+
+    logging.info(
+        f"CURV calculated base on {num_radial_points} radial points, a {radius} km radius and {tol} tolerance."
+    )
+
+    surroundings = iris.cube.CubeList([])
+    for b in bearing:
+        surround = central.copy()
+        # Need to try and avoid this loop for whole domain if possible, also need to raise time and realization bits as well.
+        for lat_number, lat in enumerate(central.slices_over("latitude")):
+            for lon_number, lon in enumerate(lat.slices_over("longitude")):
+                new_lat, new_lon = _lat_lon_identifier(
+                    lon.coord("latitude").points,
+                    lon.coord("longitude").points,
+                    radius,
+                    b,
+                )
+                # Need to get interpolation better.
+                surround.data[lat_number, lon_number] = central.data[
+                    np.abs(central.coord("latitude").points - new_lat[0]).argmin(),
+                    np.abs(central.coord("longitude").points - new_lon[0]).argmin(),
+                ]
+        surround.add_aux_coord(
+            iris.coords.DimCoord(b, long_name="bearing", units="degrees")
+        )
+        surroundings.append(surround)
+    surroundings.merge()
+    print(surroundings)
+
+    # curv = surroundings.copy()
+    # curv -= central
+
+    # curv.data[curv.data > tol]=-1.0
+    # curv.data[curv.data < tol]=1.0
+
+    # curv.collapsed('bearing',iris.analysis.SUM)
+    # curv.rename("CURV")
+    # curv.units="1"
+    # return curv

From 822af6e514cf998f72a071b3a360f145dde21baf Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 30 Apr 2026 16:05:39 +0100
Subject: [PATCH 04/17] Update to a comment for code if current testing works

---
 src/CSET/operators/curvature.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
index 4fd7511a1..2a7483f72 100644
--- a/src/CSET/operators/curvature.py
+++ b/src/CSET/operators/curvature.py
@@ -84,7 +84,7 @@ def curv(central, radius, num_radial_points=16, tol=0):
     surroundings.merge()
     print(surroundings)
 
-    # curv = surroundings.copy()
+    # curv = surroundings[0].copy()
     # curv -= central
 
     # curv.data[curv.data > tol]=-1.0

From c47033fe071d4a88cf408c8542876cba232f55bf Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 30 Apr 2026 16:09:17 +0100
Subject: [PATCH 05/17] Update to basic CURV operator

---
 src/CSET/operators/curvature.py | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
index 2a7483f72..2dca2fb06 100644
--- a/src/CSET/operators/curvature.py
+++ b/src/CSET/operators/curvature.py
@@ -84,13 +84,13 @@ def curv(central, radius, num_radial_points=16, tol=0):
     surroundings.merge()
     print(surroundings)
 
-    # curv = surroundings[0].copy()
-    # curv -= central
+    curv = surroundings[0].copy()
+    curv -= central
 
-    # curv.data[curv.data > tol]=-1.0
-    # curv.data[curv.data < tol]=1.0
+    curv.data[curv.data > tol] = -1.0
+    curv.data[curv.data < tol] = 1.0
 
-    # curv.collapsed('bearing',iris.analysis.SUM)
-    # curv.rename("CURV")
-    # curv.units="1"
-    # return curv
+    curv.collapsed("bearing", iris.analysis.SUM)
+    curv.rename(f"CURV_calculated_from_{num_radial_points}_radial_points")
+    curv.units = "1"
+    return curv

From 4c8c0952a327ffa153e249a198defb63760d5b9a Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 30 Apr 2026 16:19:52 +0100
Subject: [PATCH 06/17] Update CURV operator to show it is for global CURV

---
 src/CSET/operators/curvature.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
index 2dca2fb06..893060bad 100644
--- a/src/CSET/operators/curvature.py
+++ b/src/CSET/operators/curvature.py
@@ -47,8 +47,8 @@ def _lat_lon_identifier(original_lat, original_lon, distance, bearing):
     return new_lat, new_lon
 
 
-def curv(central, radius, num_radial_points=16, tol=0):
-    """Calculate the CURV diagnostic."""
+def global_curv(central, radius, num_radial_points=16, tol=0):
+    """Calculate the CURV diagnostic for a global model."""
     if (num_radial_points == 8) or (num_radial_points == 16):
         bearing = np.linspace(0.0, 360.0, num_radial_points + 1)[:-1]
     else:

From 3cd964b99b0ebb6fdf5d2d4df38a655eed859b69 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Wed, 13 May 2026 12:13:16 +0100
Subject: [PATCH 07/17] Adds basic recipe and plumbing into workflow

This is mainly for testing purposes to see if it works.
---
 .../meta/diagnostics/rose-meta.conf           | 12 +++++++++
 src/CSET/loaders/spatial_field.py             | 15 +++++++++++
 .../daily_weather/curv_spatial_plot.yaml      | 26 +++++++++++++++++++
 3 files changed, 53 insertions(+)
 create mode 100644 src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml

diff --git a/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf b/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
index e3fbaace3..84834adc6 100644
--- a/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
+++ b/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
@@ -1327,6 +1327,18 @@ type=python_boolean
 compulsory=true
 sort-key=dw-fog6
 
+[template variables = GLOBAL_CURV]
+ns=Diagnostics/Derived/Daily
+title=Global CURV: spatial plot
+description=PROCESS-BASED DIAGNOSTIC.
+            Determines the curvature of the MSLP field for the global model.
+            Requires air_pressure_at_mean_sea_level.
+            TEMPORARY LOCATION FOR TESTING PURPOSES.
+help=This diagnostic can be particularly useful for grouping of the data if
+     used within a recipe. This provides the plotted data.
+type=python_boolean
+compulsory=true
+sort-key=dw-curv
 ###################################
 # Aviation
 [Diagnostics/Aviation]
diff --git a/src/CSET/loaders/spatial_field.py b/src/CSET/loaders/spatial_field.py
index ba35ca1e2..8e24d2c2a 100644
--- a/src/CSET/loaders/spatial_field.py
+++ b/src/CSET/loaders/spatial_field.py
@@ -572,6 +572,21 @@ def load(conf: Config):
                 aggregation=False,
             )
 
+    if conf.GLOBAL_CURV:
+        for model in models:
+            yield RawRecipe(
+                recipe="curv_spatial_plot.yaml",
+                variables={
+                    "MODEL_NAME": model["name"],
+                    "SUBAREA_TYPE": conf.SUBAREA_TYPE if conf.SELECT_SUBAREA else None,
+                    "SUBAREA_EXTENT": conf.SUBAREA_EXTENT
+                    if conf.SELECT_SUBAREA
+                    else None,
+                },
+                model_ids=model["id"],
+                aggregation=False,
+            )
+
     # Screen-level temperature probabilities
     for model, condition, threshold in itertools.product(
         models,
diff --git a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
new file mode 100644
index 000000000..57b28a0da
--- /dev/null
+++ b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
@@ -0,0 +1,26 @@
+category: Daily Weather
+title: $MODEL_NAME CURV spatial plot
+description: |
+  Generates the curvature (CURV) from MSLP and creates a spatila plot.
+steps:
+  - operator: read.read_cubes
+    file_paths: $INPUT_PATHS
+    model_names: $MODEL_NAME
+    constraint:
+        operator: constraints.combine_constraints
+        varname_constraint:
+            operator: constraints.generate_var_constraint
+            varname: air_pressure_at_mean_sea_level
+        cell_methods_constraint:
+            operator: constraints.generate_cell_methods_constraint
+            cell_methods: []
+    subarea_type: $SUBAREA_TYPE
+    subarea_extent: $SUBAREA_EXTENT
+
+  - operator: curvature.curv
+    radius: 1000
+
+  - operator: plot.spatial_pcolormesh_plot
+
+  - operator: write.write_cube_to_nc
+    overwrite: True

From bcfce1f87f5640bb4e913e8a768960f7479e5291 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Wed, 13 May 2026 12:18:41 +0100
Subject: [PATCH 08/17] Adds CURV to example conf

---
 src/CSET/cset_workflow/rose-suite.conf.example | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/CSET/cset_workflow/rose-suite.conf.example b/src/CSET/cset_workflow/rose-suite.conf.example
index f8a730649..1997057e5 100644
--- a/src/CSET/cset_workflow/rose-suite.conf.example
+++ b/src/CSET/cset_workflow/rose-suite.conf.example
@@ -42,6 +42,7 @@ EXTRACT_PLEVEL_TRANSECT=False
 FOG_PRESENCE_DOMAIN_MEAN_TIMESERIES=False
 FOG_PRESENCE_SPATIAL_DIFFERENCE=False
 FOG_PRESENCE_SPATIAL_PLOT=False
+GLOBAL_CURV=False
 GROUND_FROST_PRESENCE_DOMAIN_MEAN_TIMESERIES=False
 GROUND_FROST_PRESENCE_SPATIAL_DIFFERENCE=False
 GROUND_FROST_PRESENCE_SPATIAL_PLOT=False

From 46b8843197d977b1a4a25aab677257418a33fad8 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Wed, 13 May 2026 12:20:15 +0100
Subject: [PATCH 09/17] Update rose-meta.conf

---
 src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf b/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
index 84834adc6..27b470a9a 100644
--- a/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
+++ b/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
@@ -1327,7 +1327,7 @@ type=python_boolean
 compulsory=true
 sort-key=dw-fog6
 
-[template variables = GLOBAL_CURV]
+[template variables=GLOBAL_CURV]
 ns=Diagnostics/Derived/Daily
 title=Global CURV: spatial plot
 description=PROCESS-BASED DIAGNOSTIC.

From abeb3aceecd79304bbba5b0e222995d191af1b0e Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Wed, 13 May 2026 15:44:25 +0100
Subject: [PATCH 10/17] Updates recipe to use the faster operator, and creates
 a tentative fast operator

This commit contains the first working version of global_curv in
global_curv_version2, global_curv is slow and has not yet produced
output.
---
 src/CSET/operators/curvature.py               | 122 +++++++++++++-----
 .../daily_weather/curv_spatial_plot.yaml      |   3 +-
 2 files changed, 92 insertions(+), 33 deletions(-)

diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
index 893060bad..ce009ca7e 100644
--- a/src/CSET/operators/curvature.py
+++ b/src/CSET/operators/curvature.py
@@ -23,6 +23,8 @@
 import iris
 import numpy as np
 
+from CSET._common import iter_maybe
+
 
 def _lat_lon_identifier(original_lat, original_lon, distance, bearing):
     """Find the latitude and longitude of new points based on great circle distance."""
@@ -59,38 +61,94 @@ def global_curv(central, radius, num_radial_points=16, tol=0):
     logging.info(
         f"CURV calculated base on {num_radial_points} radial points, a {radius} km radius and {tol} tolerance."
     )
+    curv_cubes = iris.cube.CubeList([])
+    for cube in iter_maybe(central):
+        surroundings = iris.cube.CubeList([])
+        for b in bearing:
+            surround = cube.copy()
+            # Need to try and avoid this loop for whole domain if possible, also need to raise time and realization bits as well.
+            for lat_number, lat in enumerate(cube.slices_over("latitude")):
+                for lon_number, lon in enumerate(lat.slices_over("longitude")):
+                    new_lat, new_lon = _lat_lon_identifier(
+                        lon.coord("latitude").points,
+                        lon.coord("longitude").points,
+                        radius,
+                        b,
+                    )
+                    # Need to get interpolation better.
+                    surround.data[:, lat_number, lon_number] = cube.data[
+                        :,
+                        np.abs(cube.coord("latitude").points - new_lat[0]).argmin(),
+                        np.abs(cube.coord("longitude").points - new_lon[0]).argmin(),
+                    ]
+            surround.add_aux_coord(
+                iris.coords.DimCoord(b, long_name="bearing", units="degrees")
+            )
+            surroundings.append(surround)
+        surroundings.merge()
+        print(surroundings)
+
+        curv = surroundings[0].copy()
+        curv -= cube
+
+        curv.data[curv.data > tol] = -1.0
+        curv.data[curv.data < tol] = 1.0
+
+        curv.collapsed("bearing", iris.analysis.SUM)
+        curv.rename(f"CURV_calculated_from_{num_radial_points}_radial_points")
+        curv.units = "1"
+        curv_cubes.append(curv)
+    if len(curv_cubes) == 1:
+        return curv_cubes[0]
+    else:
+        return curv_cubes
 
-    surroundings = iris.cube.CubeList([])
-    for b in bearing:
-        surround = central.copy()
-        # Need to try and avoid this loop for whole domain if possible, also need to raise time and realization bits as well.
-        for lat_number, lat in enumerate(central.slices_over("latitude")):
-            for lon_number, lon in enumerate(lat.slices_over("longitude")):
-                new_lat, new_lon = _lat_lon_identifier(
-                    lon.coord("latitude").points,
-                    lon.coord("longitude").points,
-                    radius,
-                    b,
-                )
-                # Need to get interpolation better.
-                surround.data[lat_number, lon_number] = central.data[
-                    np.abs(central.coord("latitude").points - new_lat[0]).argmin(),
-                    np.abs(central.coord("longitude").points - new_lon[0]).argmin(),
-                ]
-        surround.add_aux_coord(
-            iris.coords.DimCoord(b, long_name="bearing", units="degrees")
-        )
-        surroundings.append(surround)
-    surroundings.merge()
-    print(surroundings)
-
-    curv = surroundings[0].copy()
-    curv -= central
 
-    curv.data[curv.data > tol] = -1.0
-    curv.data[curv.data < tol] = 1.0
+def global_curv_versiontwo(central, radius, num_radial_points=16, tol=0.0):
+    """Calculate the CURV diagnostic for a global model VERSION 2 for faster calculation speed."""
+    if (num_radial_points == 8) or (num_radial_points == 16):
+        bearing = np.linspace(0.0, 360.0, num_radial_points + 1)[:-1]
+    else:
+        raise ValueError(
+            f"Number of radial points should be 8 or 16. You have provided {num_radial_points}."
+        )
 
-    curv.collapsed("bearing", iris.analysis.SUM)
-    curv.rename(f"CURV_calculated_from_{num_radial_points}_radial_points")
-    curv.units = "1"
-    return curv
+    logging.info(
+        f"CURV calculated base on {num_radial_points} radial points, a {radius} km radius and {tol} tolerance."
+    )
+    curv_cubes = iris.cube.CubeList([])
+    for cube in iter_maybe(central):
+        curv = cube.copy()
+        surroundings = []
+        lats, lons = np.meshgrid(
+            cube.coord("latitude").points, cube.coord("longitude").points
+        )
+        for b in bearing:
+            target_data = cube.copy()
+            new_lat, new_lon = _lat_lon_identifier(
+                lats,
+                lons,
+                radius,
+                b,
+            )
+            new_lat_points = new_lat[0, :]
+            new_lon_points = new_lon[:, 0]
+            surround = target_data.interpolate(
+                [("latitude", new_lat_points), ("longitude", new_lon_points)],
+                iris.analysis.Nearest(),
+            )
+            surroundings.append(surround.data)
+        surroundings = np.array(surroundings)
+        curv_data = surroundings - cube.data
+        curv_data_binary = np.zeros(curv_data.shape)
+        curv_data_binary[curv_data > tol] = -1.0
+        curv_data_binary[curv_data < tol] = 1.0
+        curv_data_collapsed = np.sum(curv_data_binary, 0)
+        curv.data = curv_data_collapsed
+        curv.rename(f"CURV_calculated_from_{num_radial_points}_radial_points")
+        curv.units = "1"
+        curv_cubes.append(curv)
+    if len(curv_cubes) == 1:
+        return curv_cubes[0]
+    else:
+        return curv_cubes
diff --git a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
index 57b28a0da..db97a3f16 100644
--- a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
+++ b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
@@ -17,8 +17,9 @@ steps:
     subarea_type: $SUBAREA_TYPE
     subarea_extent: $SUBAREA_EXTENT
 
-  - operator: curvature.curv
+  - operator: curvature.global_curv_versiontwo
     radius: 1000
+    num_radial_points: 8
 
   - operator: plot.spatial_pcolormesh_plot
 

From db3fd66b1924a3640ebbc5392c3c39d7bee2e438 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 14 May 2026 13:27:26 +0100
Subject: [PATCH 11/17] Switches to linear interpolation and adds options to
 change radius and number of points in gui

---
 .../meta/diagnostics/rose-meta.conf            | 18 +++++++++++++++++-
 src/CSET/loaders/spatial_field.py              |  6 +++++-
 src/CSET/operators/curvature.py                |  2 +-
 .../daily_weather/curv_spatial_plot.yaml       | 10 ++++++----
 4 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf b/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
index 27b470a9a..1c53be724 100644
--- a/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
+++ b/src/CSET/cset_workflow/meta/diagnostics/rose-meta.conf
@@ -1338,7 +1338,23 @@ help=This diagnostic can be particularly useful for grouping of the data if
      used within a recipe. This provides the plotted data.
 type=python_boolean
 compulsory=true
-sort-key=dw-curv
+sort-key=dw-curv3
+
+[template variables=CURV_POINTS]
+ns=Diagnostics/Derived/Daily
+title=Number of points to use in CURV
+description=The number of points to use in CURV calculation. This should be 8 or 16.
+type=python_list
+compulsory=true
+sort-key=dw-curv1
+
+[template variables=CURV_RADIUS]
+ns=Diagnostics/Derived/Daily
+title=Radii to use in CURV
+description=The radii in km to use in CURV calculation.
+type=python_list
+compulsory=true
+sort-key=dw-curv2
 ###################################
 # Aviation
 [Diagnostics/Aviation]
diff --git a/src/CSET/loaders/spatial_field.py b/src/CSET/loaders/spatial_field.py
index 8e24d2c2a..aa91b79ab 100644
--- a/src/CSET/loaders/spatial_field.py
+++ b/src/CSET/loaders/spatial_field.py
@@ -573,11 +573,15 @@ def load(conf: Config):
             )
 
     if conf.GLOBAL_CURV:
-        for model in models:
+        for model, points, radius in itertools.product(
+            models, conf.CURV_POINTS, conf.CURV_RADIUS
+        ):
             yield RawRecipe(
                 recipe="curv_spatial_plot.yaml",
                 variables={
                     "MODEL_NAME": model["name"],
+                    "CURV_POINTS": points,
+                    "CURV_RADIUS": radius,
                     "SUBAREA_TYPE": conf.SUBAREA_TYPE if conf.SELECT_SUBAREA else None,
                     "SUBAREA_EXTENT": conf.SUBAREA_EXTENT
                     if conf.SELECT_SUBAREA
diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
index ce009ca7e..3b30c3f44 100644
--- a/src/CSET/operators/curvature.py
+++ b/src/CSET/operators/curvature.py
@@ -135,7 +135,7 @@ def global_curv_versiontwo(central, radius, num_radial_points=16, tol=0.0):
             new_lon_points = new_lon[:, 0]
             surround = target_data.interpolate(
                 [("latitude", new_lat_points), ("longitude", new_lon_points)],
-                iris.analysis.Nearest(),
+                iris.analysis.Linear(),
             )
             surroundings.append(surround.data)
         surroundings = np.array(surroundings)
diff --git a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
index db97a3f16..87e55b2d3 100644
--- a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
+++ b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
@@ -1,7 +1,9 @@
 category: Daily Weather
-title: $MODEL_NAME CURV spatial plot
+title: $MODEL_NAME CURV spatial plot from $CURV_POINTS points and radius of $CURV_RADIUS km
 description: |
-  Generates the curvature (CURV) from MSLP and creates a spatila plot.
+  Generates the curvature (CURV) from MSLP and creates a spatial plot.
+  It uses $CURV_POINTS points and a radius of $CURV_RADIUS km.
+  +$CURV_POINTS is a full anticyclone and -$CURV_POINTS is a full cyclone.
 steps:
   - operator: read.read_cubes
     file_paths: $INPUT_PATHS
@@ -18,8 +20,8 @@ steps:
     subarea_extent: $SUBAREA_EXTENT
 
   - operator: curvature.global_curv_versiontwo
-    radius: 1000
-    num_radial_points: 8
+    radius: $CURV_RADIUS
+    num_radial_points: $CURV_POINTS
 
   - operator: plot.spatial_pcolormesh_plot
 

From 08a5049fef2d62be5601f2b67e7ed2a87d697913 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 14 May 2026 13:29:53 +0100
Subject: [PATCH 12/17] Removes slow version of code, renames fast version,
 updates recipe

---
 src/CSET/operators/curvature.py               | 57 +------------------
 .../daily_weather/curv_spatial_plot.yaml      |  2 +-
 2 files changed, 2 insertions(+), 57 deletions(-)

diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
index 3b30c3f44..c29b75c27 100644
--- a/src/CSET/operators/curvature.py
+++ b/src/CSET/operators/curvature.py
@@ -49,62 +49,7 @@ def _lat_lon_identifier(original_lat, original_lon, distance, bearing):
     return new_lat, new_lon
 
 
-def global_curv(central, radius, num_radial_points=16, tol=0):
-    """Calculate the CURV diagnostic for a global model."""
-    if (num_radial_points == 8) or (num_radial_points == 16):
-        bearing = np.linspace(0.0, 360.0, num_radial_points + 1)[:-1]
-    else:
-        raise ValueError(
-            f"Number of radial points should be 8 or 16. You have provided {num_radial_points}."
-        )
-
-    logging.info(
-        f"CURV calculated base on {num_radial_points} radial points, a {radius} km radius and {tol} tolerance."
-    )
-    curv_cubes = iris.cube.CubeList([])
-    for cube in iter_maybe(central):
-        surroundings = iris.cube.CubeList([])
-        for b in bearing:
-            surround = cube.copy()
-            # Need to try and avoid this loop for whole domain if possible, also need to raise time and realization bits as well.
-            for lat_number, lat in enumerate(cube.slices_over("latitude")):
-                for lon_number, lon in enumerate(lat.slices_over("longitude")):
-                    new_lat, new_lon = _lat_lon_identifier(
-                        lon.coord("latitude").points,
-                        lon.coord("longitude").points,
-                        radius,
-                        b,
-                    )
-                    # Need to get interpolation better.
-                    surround.data[:, lat_number, lon_number] = cube.data[
-                        :,
-                        np.abs(cube.coord("latitude").points - new_lat[0]).argmin(),
-                        np.abs(cube.coord("longitude").points - new_lon[0]).argmin(),
-                    ]
-            surround.add_aux_coord(
-                iris.coords.DimCoord(b, long_name="bearing", units="degrees")
-            )
-            surroundings.append(surround)
-        surroundings.merge()
-        print(surroundings)
-
-        curv = surroundings[0].copy()
-        curv -= cube
-
-        curv.data[curv.data > tol] = -1.0
-        curv.data[curv.data < tol] = 1.0
-
-        curv.collapsed("bearing", iris.analysis.SUM)
-        curv.rename(f"CURV_calculated_from_{num_radial_points}_radial_points")
-        curv.units = "1"
-        curv_cubes.append(curv)
-    if len(curv_cubes) == 1:
-        return curv_cubes[0]
-    else:
-        return curv_cubes
-
-
-def global_curv_versiontwo(central, radius, num_radial_points=16, tol=0.0):
+def global_curv(central, radius, num_radial_points=16, tol=0.0):
     """Calculate the CURV diagnostic for a global model VERSION 2 for faster calculation speed."""
     if (num_radial_points == 8) or (num_radial_points == 16):
         bearing = np.linspace(0.0, 360.0, num_radial_points + 1)[:-1]
diff --git a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
index 87e55b2d3..14e09add8 100644
--- a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
+++ b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
@@ -19,7 +19,7 @@ steps:
     subarea_type: $SUBAREA_TYPE
     subarea_extent: $SUBAREA_EXTENT
 
-  - operator: curvature.global_curv_versiontwo
+  - operator: curvature.global_curv
     radius: $CURV_RADIUS
     num_radial_points: $CURV_POINTS
 

From 74c13daf1f9e57afc6ab0796deb0ac67e1ba8412 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 14 May 2026 17:01:52 +0100
Subject: [PATCH 13/17] Adds new colorbar for curv

---
 src/CSET/operators/plot.py | 63 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index c6a44e09b..e026a0aed 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -285,6 +285,9 @@ def _colorbar_map_levels(cube: iris.cube.Cube, axis: Literal["x", "y"] | None =
     if any("aviation_colour_state" in name for name in varnames):
         cmap, levels, norm = _custom_colormap_aviation_colour_state(cube)
         return cmap, levels, norm
+    if any("CURV_" in name for name in varnames):
+        cmap, levels, norm = _custom_colormap_curv(cube)
+        return cmap, levels, norm
 
     # If no valid colormap has been defined, use defaults and return.
     if not cmap:
@@ -2293,6 +2296,66 @@ def _custom_colormap_aviation_colour_state(cube: iris.cube.Cube):
     return cmap, levels, norm
 
 
+def _custom_colormap_curv(cube: iris.cube.Cube):
+    """Return custom colourmap for curv.
+
+    If "CURV_" appears anywhere in the name of a cube
+    this function will be called.
+
+    Parameters
+    ----------
+    cube: Cube
+        Cube of variable for which the colorbar information is desired.
+
+    Returns
+    -------
+    cmap: Matplotlib colormap.
+    levels: List
+        List of levels to use for plotting. For continuous plots the min and max
+        should be taken as the range.
+    norm: BoundaryNorm.
+    """
+    if "8" in cube.long_name():
+        levels = [-17, -15, -13, -11, -9, -7, -5, -3, -1, 1, 3, 5, 7, 9, 11, 13, 15, 17]
+        colors = [
+            "#ff0000",
+            "#a52a2a",
+            "#dc143c",
+            "#ff4500",
+            "#f97306",
+            "#ffa500",
+            "#fac205",
+            "#ffd700",
+            "#ffffff",
+            "#7fffd4",
+            "#00ffff",
+            "#069af3",
+            "#0323df",
+            "#0000ff",
+            "#00008b",
+            "#030764",
+            "#01153e",
+        ]
+    else:
+        levels = [-9, -7, -5, -3, -1, 1, 3, 5, 7, 9]
+        colors = [
+            "#ff0000",
+            "#dc143c",
+            "#f97306",
+            "#fac205",
+            "#ffffff",
+            "#00ffff",
+            "#0323df",
+            "#00008b",
+            "#01153e",
+        ]
+        # Create a custom colormap
+        cmap = mcolors.ListedColormap(colors)
+        # Normalise the levels
+        norm = mcolors.BoundaryNorm(levels, cmap.N)
+    return cmap, levels, norm
+
+
 def _custom_colourmap_visibility_in_air(cube: iris.cube.Cube, cmap, levels, norm):
     """Return a custom colourmap for the current recipe."""
     varnames = filter(None, [cube.long_name, cube.standard_name, cube.var_name])

From d3482a32946e2b95a3b6827b1d80b4bc195ff1cf Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 14 May 2026 17:07:26 +0100
Subject: [PATCH 14/17] Updates colorbar

---
 src/CSET/operators/plot.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index e026a0aed..d7dd5aa91 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -2315,7 +2315,7 @@ def _custom_colormap_curv(cube: iris.cube.Cube):
         should be taken as the range.
     norm: BoundaryNorm.
     """
-    if "8" in cube.long_name():
+    if "8" in cube.long_name:
         levels = [-17, -15, -13, -11, -9, -7, -5, -3, -1, 1, 3, 5, 7, 9, 11, 13, 15, 17]
         colors = [
             "#ff0000",

From 0cc4925a38fdbbfae02f25b4893c18471c8521c0 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Thu, 14 May 2026 17:14:06 +0100
Subject: [PATCH 15/17] Updates colorbar

---
 src/CSET/operators/plot.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index d7dd5aa91..3b7ec7402 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -2315,7 +2315,7 @@ def _custom_colormap_curv(cube: iris.cube.Cube):
         should be taken as the range.
     norm: BoundaryNorm.
     """
-    if "8" in cube.long_name:
+    if "16" in cube.long_name:
         levels = [-17, -15, -13, -11, -9, -7, -5, -3, -1, 1, 3, 5, 7, 9, 11, 13, 15, 17]
         colors = [
             "#ff0000",
@@ -2349,10 +2349,10 @@ def _custom_colormap_curv(cube: iris.cube.Cube):
             "#00008b",
             "#01153e",
         ]
-        # Create a custom colormap
-        cmap = mcolors.ListedColormap(colors)
-        # Normalise the levels
-        norm = mcolors.BoundaryNorm(levels, cmap.N)
+    # Create a custom colormap
+    cmap = mcolors.ListedColormap(colors)
+    # Normalise the levels
+    norm = mcolors.BoundaryNorm(levels, cmap.N)
     return cmap, levels, norm
 
 

From 22aa95e5dda40359ed3763bc3c53762150fbf265 Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Fri, 15 May 2026 15:39:56 +0100
Subject: [PATCH 16/17] Update colorbar and default tolerance

---
 src/CSET/operators/curvature.py |  6 ++---
 src/CSET/operators/plot.py      | 46 ++++++++++++++++-----------------
 2 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/src/CSET/operators/curvature.py b/src/CSET/operators/curvature.py
index c29b75c27..834fd6014 100644
--- a/src/CSET/operators/curvature.py
+++ b/src/CSET/operators/curvature.py
@@ -44,12 +44,12 @@ def _lat_lon_identifier(original_lat, original_lon, distance, bearing):
 
     new_lat = np.degrees(new_lat)
     new_lon = np.degrees(new_lon)
-    new_lon = np.where(new_lon > 360.0, new_lon - 360.0, new_lon)
+    new_lon = np.where(new_lon > 180.0, new_lon - 360.0, new_lon)
 
     return new_lat, new_lon
 
 
-def global_curv(central, radius, num_radial_points=16, tol=0.0):
+def global_curv(central, radius, num_radial_points=16, tol=400.0):
     """Calculate the CURV diagnostic for a global model VERSION 2 for faster calculation speed."""
     if (num_radial_points == 8) or (num_radial_points == 16):
         bearing = np.linspace(0.0, 360.0, num_radial_points + 1)[:-1]
@@ -87,7 +87,7 @@ def global_curv(central, radius, num_radial_points=16, tol=0.0):
         curv_data = surroundings - cube.data
         curv_data_binary = np.zeros(curv_data.shape)
         curv_data_binary[curv_data > tol] = -1.0
-        curv_data_binary[curv_data < tol] = 1.0
+        curv_data_binary[curv_data < -tol] = 1.0
         curv_data_collapsed = np.sum(curv_data_binary, 0)
         curv.data = curv_data_collapsed
         curv.rename(f"CURV_calculated_from_{num_radial_points}_radial_points")
diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 3b7ec7402..dd55f62b8 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -2318,36 +2318,36 @@ def _custom_colormap_curv(cube: iris.cube.Cube):
     if "16" in cube.long_name:
         levels = [-17, -15, -13, -11, -9, -7, -5, -3, -1, 1, 3, 5, 7, 9, 11, 13, 15, 17]
         colors = [
+            "#01153e",
+            "#030764",
+            "#00008b",
+            "#0000ff",
+            "#0323df",
+            "#069af3",
+            "#00ffff",
+            "#7fffd4",
+            "#ffffff",
+            "#ffd700",
+            "#fac205",
+            "#ffa500",
+            "#f97306",
+            "#ff4500",
             "#ff0000",
-            "#a52a2a",
             "#dc143c",
-            "#ff4500",
-            "#f97306",
-            "#ffa500",
-            "#fac205",
-            "#ffd700",
-            "#ffffff",
-            "#7fffd4",
-            "#00ffff",
-            "#069af3",
-            "#0323df",
-            "#0000ff",
-            "#00008b",
-            "#030764",
-            "#01153e",
+            "#a52a2a",
         ]
     else:
         levels = [-9, -7, -5, -3, -1, 1, 3, 5, 7, 9]
         colors = [
-            "#ff0000",
-            "#dc143c",
-            "#f97306",
-            "#fac205",
-            "#ffffff",
-            "#00ffff",
-            "#0323df",
-            "#00008b",
             "#01153e",
+            "#00008b",
+            "#0323df",
+            "#00ffff",
+            "#ffffff",
+            "#fac205",
+            "#f97306",
+            "#ff0000",
+            "#a52a2a",
         ]
     # Create a custom colormap
     cmap = mcolors.ListedColormap(colors)

From a4f633d794a7df690c40753e2543c1b3e4fbf9cb Mon Sep 17 00:00:00 2001
From: daflack <david.flack1@metoffice.gov.uk>
Date: Fri, 15 May 2026 16:30:37 +0100
Subject: [PATCH 17/17] Adds regridding to recipe

---
 .../daily_weather/curv_spatial_plot.yaml                    | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
index 14e09add8..846fc575d 100644
--- a/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
+++ b/src/CSET/recipes/derived_diagnostics/daily_weather/curv_spatial_plot.yaml
@@ -19,9 +19,15 @@ steps:
     subarea_type: $SUBAREA_TYPE
     subarea_extent: $SUBAREA_EXTENT
 
+  - operator: regrid.regrid_onto_xyspacing
+    xspacing: 1.0
+    yspacing: 1.0
+    method: Linear
+
   - operator: curvature.global_curv
     radius: $CURV_RADIUS
     num_radial_points: $CURV_POINTS
+    tol: 400.0
 
   - operator: plot.spatial_pcolormesh_plot