From d41a72d9af268288780bd6bfd4f705129978989f Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Wed, 19 Mar 2025 17:31:03 +0000
Subject: [PATCH 01/13] introduce callback function to convert precipitation
 units to mm hr-1. Colourbar scale changed accordingly for
 surface_microphysical_rainfall_rate. Still requires change to colourbar

---
 src/CSET/operators/_colorbar_definition.json |  2 +-
 src/CSET/operators/read.py                   | 31 ++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/CSET/operators/_colorbar_definition.json b/src/CSET/operators/_colorbar_definition.json
index 2cb58eb59..372caa636 100644
--- a/src/CSET/operators/_colorbar_definition.json
+++ b/src/CSET/operators/_colorbar_definition.json
@@ -392,7 +392,7 @@
   },
   "surface_microphysical_rainfall_rate": {
     "cmap": "cividis",
-    "max": 0.001,
+    "max": 256.0,
     "min": 0
   },
   "surface_microphysical_rainfall_rate_difference": {
diff --git a/src/CSET/operators/read.py b/src/CSET/operators/read.py
index 896a53929..c4ab0a7a4 100644
--- a/src/CSET/operators/read.py
+++ b/src/CSET/operators/read.py
@@ -240,6 +240,7 @@ def callback(cube: iris.cube.Cube, field, filename: str):
         _fix_lfric_longnames(cube)
         _fix_um_lightning(cube)
         _lfric_time_callback(cube)
+        _convert_precipitation_units(cube)
 
     return callback
 
@@ -665,3 +666,33 @@ def _check_input_files(input_paths: list[str], filename_pattern: str) -> list[Pa
     if len(files) == 0:
         raise FileNotFoundError(f"No files found for {input_paths}")
     return files
+
+
+def _convert_precipitation_units(cube: iris.cube.Cube):
+    """To convert the unit of precipitation from kg m-2 s-1 to mm hr-1.
+
+    Some precipitation diagnostics are output with unit kg m-2 s-1 and are converted to mm hr-1.
+    """
+    try:
+        # if cube.attributes["STASH"] == "m01s04i203" or cube.long_name == "surface_microphysical_rainfall_rate":
+        if cube.long_name == "surface_microphysical_rainfall_rate":
+            if cube.units == "kg m-2 s-1":
+                logging.info(
+                    "Converting precipitation units from kg m-2 s-1 to mm hr-1"
+                )
+                # manually convert from kg m-2 s-1 to mm hr-1 assuming 1kg water = 1l water = 1dm^3 water
+                cube.data = cube.data * 3600.0
+
+                # update the units
+                cube.units = "mm hr-1"
+            else:
+                logging.warning(
+                    "Precipitation units are not in 'kg m-2 s-1', skipping conversion"
+                )
+    except iris.exceptions.CoordinateNotFoundError:
+        logging.warning(
+            "Precipitation cube does not contain the required coordinate, skipping conversion"
+        )
+    except KeyError:
+        logging.warning("STASH attribute not found in cube, cannot convert units")
+    return cube

From 16ea41545380e6c8ba56b09dd948b47ca961832b Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Thu, 20 Mar 2025 14:55:41 +0000
Subject: [PATCH 02/13] moved callback function for converting precipitation
 units from read operator into plot operator

---
 src/CSET/operators/plot.py | 36 ++++++++++++++++++++++++++++++++++++
 src/CSET/operators/read.py | 31 -------------------------------
 2 files changed, 36 insertions(+), 31 deletions(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 848eef666..0b5f1b9c4 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -975,6 +975,9 @@ def spatial_contour_plot(
     TypeError
         If the cube isn't a single cube.
     """
+    # Convert precipitation units if necessary
+    _convert_precipitation_units_callback(cube)
+
     _spatial_plot("contourf", cube, filename, sequence_coordinate, stamp_coordinate)
     return cube
 
@@ -1024,6 +1027,9 @@ def spatial_pcolormesh_plot(
     TypeError
         If the cube isn't a single cube.
     """
+    # Convert precipitation units if necessary
+    _convert_precipitation_units_callback(cube)
+
     _spatial_plot("pcolormesh", cube, filename, sequence_coordinate, stamp_coordinate)
     return cube
 
@@ -1479,3 +1485,33 @@ def plot_histogram_series(
     _make_plot_html_page(complete_plot_index)
 
     return cubes
+
+
+def _convert_precipitation_units_callback(cube: iris.cube.Cube):
+    """To convert the unit of precipitation from kg m-2 s-1 to mm hr-1.
+
+    Some precipitation diagnostics are output with unit kg m-2 s-1 and are converted to mm hr-1.
+    """
+    try:
+        # if cube.attributes["STASH"] == "m01s04i203" or cube.long_name == "surface_microphysical_rainfall_rate":
+        if cube.long_name == "surface_microphysical_rainfall_rate":
+            if cube.units == "kg m-2 s-1":
+                logging.info(
+                    "Converting precipitation units from kg m-2 s-1 to mm hr-1"
+                )
+                # manually convert from kg m-2 s-1 to mm hr-1 assuming 1kg water = 1l water = 1dm^3 water
+                cube.data = cube.data * 3600.0
+
+                # update the units
+                cube.units = "mm hr-1"
+            else:
+                logging.warning(
+                    "Precipitation units are not in 'kg m-2 s-1', skipping conversion"
+                )
+    except iris.exceptions.CoordinateNotFoundError:
+        logging.warning(
+            "Precipitation cube does not contain the required coordinate, skipping conversion"
+        )
+    except KeyError:
+        logging.warning("STASH attribute not found in cube, cannot convert units")
+    return cube
diff --git a/src/CSET/operators/read.py b/src/CSET/operators/read.py
index c4ab0a7a4..896a53929 100644
--- a/src/CSET/operators/read.py
+++ b/src/CSET/operators/read.py
@@ -240,7 +240,6 @@ def callback(cube: iris.cube.Cube, field, filename: str):
         _fix_lfric_longnames(cube)
         _fix_um_lightning(cube)
         _lfric_time_callback(cube)
-        _convert_precipitation_units(cube)
 
     return callback
 
@@ -666,33 +665,3 @@ def _check_input_files(input_paths: list[str], filename_pattern: str) -> list[Pa
     if len(files) == 0:
         raise FileNotFoundError(f"No files found for {input_paths}")
     return files
-
-
-def _convert_precipitation_units(cube: iris.cube.Cube):
-    """To convert the unit of precipitation from kg m-2 s-1 to mm hr-1.
-
-    Some precipitation diagnostics are output with unit kg m-2 s-1 and are converted to mm hr-1.
-    """
-    try:
-        # if cube.attributes["STASH"] == "m01s04i203" or cube.long_name == "surface_microphysical_rainfall_rate":
-        if cube.long_name == "surface_microphysical_rainfall_rate":
-            if cube.units == "kg m-2 s-1":
-                logging.info(
-                    "Converting precipitation units from kg m-2 s-1 to mm hr-1"
-                )
-                # manually convert from kg m-2 s-1 to mm hr-1 assuming 1kg water = 1l water = 1dm^3 water
-                cube.data = cube.data * 3600.0
-
-                # update the units
-                cube.units = "mm hr-1"
-            else:
-                logging.warning(
-                    "Precipitation units are not in 'kg m-2 s-1', skipping conversion"
-                )
-    except iris.exceptions.CoordinateNotFoundError:
-        logging.warning(
-            "Precipitation cube does not contain the required coordinate, skipping conversion"
-        )
-    except KeyError:
-        logging.warning("STASH attribute not found in cube, cannot convert units")
-    return cube

From 82b44c99a40d77acd09d070eee5ccc3b107826ed Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Thu, 20 Mar 2025 17:30:57 +0000
Subject: [PATCH 03/13] remove vmin and vmax from call if norm is already
 supplied. Not sure this is correct.

---
 src/CSET/operators/_colorbar_definition.json | 14 ++++++++++++--
 src/CSET/operators/plot.py                   | 13 +++++++------
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/CSET/operators/_colorbar_definition.json b/src/CSET/operators/_colorbar_definition.json
index 372caa636..c06f7ac39 100644
--- a/src/CSET/operators/_colorbar_definition.json
+++ b/src/CSET/operators/_colorbar_definition.json
@@ -392,8 +392,18 @@
   },
   "surface_microphysical_rainfall_rate": {
     "cmap": "cividis",
-    "max": 256.0,
-    "min": 0
+    "levels": [
+      0.125,
+      0.25,
+      0.5,
+      1,
+      2,
+      4,
+      8,
+      16,
+      32,
+      64
+    ]
   },
   "surface_microphysical_rainfall_rate_difference": {
     "cmap": "bwr",
diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 0b5f1b9c4..b25709c76 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -245,6 +245,7 @@ def _colorbar_map_levels(cube: iris.cube.Cube):
                 # smooth range.
                 norm = mpl.colors.BoundaryNorm(levels, ncolors=cmap.N)
                 logging.debug("Using levels for %s colorbar.", varname)
+                logging.info("Using levels: %s", levels)
             except KeyError:
                 # Get the range for this variable.
                 vmin, vmax = var_colorbar["min"], var_colorbar["max"]
@@ -299,13 +300,13 @@ def _plot_and_save_spatial_plot(
         # Filled contour plot of the field.
         plot = iplt.contourf(cube, cmap=cmap, levels=levels, norm=norm)
     elif method == "pcolormesh":
-        try:
-            vmin = min(levels)
-            vmax = max(levels)
-        except TypeError:
-            vmin, vmax = None, None
+        # try:
+        #    vmin = min(levels)
+        #    vmax = max(levels)
+        # except TypeError:
+        # vmin, vmax = None, None
         # pcolormesh plot of the field.
-        plot = iplt.pcolormesh(cube, cmap=cmap, norm=norm, vmin=vmin, vmax=vmax)
+        plot = iplt.pcolormesh(cube, cmap=cmap, norm=norm)
     else:
         raise ValueError(f"Unknown plotting method: {method}")
 

From 88033c245229d032fed973e85b1e1d743d2dfd95 Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Tue, 25 Mar 2025 11:43:09 +0000
Subject: [PATCH 04/13] moving ppn unit conversion into _plot_spatial

---
 src/CSET/operators/plot.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index b25709c76..7e5570fc6 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -889,6 +889,9 @@ def _spatial_plot(
     # Ensure we've got a single cube.
     cube = _check_single_cube(cube)
 
+    # Convert precipitation units if necessary
+    _convert_precipitation_units_callback(cube)
+
     # Make postage stamp plots if stamp_coordinate exists and has more than a
     # single point.
     plotting_func = _plot_and_save_spatial_plot
@@ -976,9 +979,6 @@ def spatial_contour_plot(
     TypeError
         If the cube isn't a single cube.
     """
-    # Convert precipitation units if necessary
-    _convert_precipitation_units_callback(cube)
-
     _spatial_plot("contourf", cube, filename, sequence_coordinate, stamp_coordinate)
     return cube
 

From 491ea35778bd80c29576987f9beb7a422205b1c1 Mon Sep 17 00:00:00 2001
From: Sylvia Bohnenstengel
 <62748926+Sylviabohnenstengel@users.noreply.github.com>
Date: Tue, 25 Mar 2025 11:54:45 +0000
Subject: [PATCH 05/13] Update src/CSET/operators/plot.py

Co-authored-by: James Frost <james.frost@metoffice.gov.uk>
---
 src/CSET/operators/plot.py | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 7e5570fc6..6ab60dcfb 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -1509,10 +1509,4 @@ def _convert_precipitation_units_callback(cube: iris.cube.Cube):
                 logging.warning(
                     "Precipitation units are not in 'kg m-2 s-1', skipping conversion"
                 )
-    except iris.exceptions.CoordinateNotFoundError:
-        logging.warning(
-            "Precipitation cube does not contain the required coordinate, skipping conversion"
-        )
-    except KeyError:
-        logging.warning("STASH attribute not found in cube, cannot convert units")
     return cube

From b5c15fa67a8b7533e0a5687f26804f3ae99e8d71 Mon Sep 17 00:00:00 2001
From: Sylvia Bohnenstengel
 <62748926+Sylviabohnenstengel@users.noreply.github.com>
Date: Tue, 25 Mar 2025 11:55:22 +0000
Subject: [PATCH 06/13] Update src/CSET/operators/plot.py

Co-authored-by: James Frost <james.frost@metoffice.gov.uk>
---
 src/CSET/operators/plot.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 6ab60dcfb..b9cfe15e6 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -1493,7 +1493,6 @@ def _convert_precipitation_units_callback(cube: iris.cube.Cube):
 
     Some precipitation diagnostics are output with unit kg m-2 s-1 and are converted to mm hr-1.
     """
-    try:
         # if cube.attributes["STASH"] == "m01s04i203" or cube.long_name == "surface_microphysical_rainfall_rate":
         if cube.long_name == "surface_microphysical_rainfall_rate":
             if cube.units == "kg m-2 s-1":

From b882497b4eb4c9f0bcadcbb712d094c685f95598 Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Tue, 25 Mar 2025 12:10:39 +0000
Subject: [PATCH 07/13] fix indentation issue

---
 src/CSET/operators/plot.py | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index b9cfe15e6..989e5c4a6 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -1493,19 +1493,17 @@ def _convert_precipitation_units_callback(cube: iris.cube.Cube):
 
     Some precipitation diagnostics are output with unit kg m-2 s-1 and are converted to mm hr-1.
     """
-        # if cube.attributes["STASH"] == "m01s04i203" or cube.long_name == "surface_microphysical_rainfall_rate":
-        if cube.long_name == "surface_microphysical_rainfall_rate":
-            if cube.units == "kg m-2 s-1":
-                logging.info(
-                    "Converting precipitation units from kg m-2 s-1 to mm hr-1"
-                )
-                # manually convert from kg m-2 s-1 to mm hr-1 assuming 1kg water = 1l water = 1dm^3 water
-                cube.data = cube.data * 3600.0
-
-                # update the units
-                cube.units = "mm hr-1"
-            else:
-                logging.warning(
-                    "Precipitation units are not in 'kg m-2 s-1', skipping conversion"
-                )
+    # if cube.attributes["STASH"] == "m01s04i203" or cube.long_name == "surface_microphysical_rainfall_rate":
+    if cube.long_name == "surface_microphysical_rainfall_rate":
+        if cube.units == "kg m-2 s-1":
+            logging.info("Converting precipitation units from kg m-2 s-1 to mm hr-1")
+            # manually convert from kg m-2 s-1 to mm hr-1 assuming 1kg water = 1l water = 1dm^3 water
+            cube.data = cube.data * 3600.0
+
+            # update the units
+            cube.units = "mm hr-1"
+        else:
+            logging.warning(
+                "Precipitation units are not in 'kg m-2 s-1', skipping conversion"
+            )
     return cube

From 3f8132dd76d9b0986df086310e1e13dcf49b7157 Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Tue, 25 Mar 2025 12:31:53 +0000
Subject: [PATCH 08/13] move function into private section

---
 src/CSET/operators/plot.py | 42 +++++++++++++++++++-------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 989e5c4a6..e63aee68a 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -933,6 +933,27 @@ def _spatial_plot(
     _make_plot_html_page(complete_plot_index)
 
 
+def _convert_precipitation_units_callback(cube: iris.cube.Cube):
+    """To convert the unit of precipitation from kg m-2 s-1 to mm hr-1.
+
+    Some precipitation diagnostics are output with unit kg m-2 s-1 and are converted to mm hr-1.
+    """
+    # if cube.attributes["STASH"] == "m01s04i203" or cube.long_name == "surface_microphysical_rainfall_rate":
+    if cube.long_name == "surface_microphysical_rainfall_rate":
+        if cube.units == "kg m-2 s-1":
+            logging.info("Converting precipitation units from kg m-2 s-1 to mm hr-1")
+            # manually convert from kg m-2 s-1 to mm hr-1 assuming 1kg water = 1l water = 1dm^3 water
+            cube.data = cube.data * 3600.0
+
+            # update the units
+            cube.units = "mm hr-1"
+        else:
+            logging.warning(
+                "Precipitation units are not in 'kg m-2 s-1', skipping conversion"
+            )
+    return cube
+
+
 ####################
 # Public functions #
 ####################
@@ -1486,24 +1507,3 @@ def plot_histogram_series(
     _make_plot_html_page(complete_plot_index)
 
     return cubes
-
-
-def _convert_precipitation_units_callback(cube: iris.cube.Cube):
-    """To convert the unit of precipitation from kg m-2 s-1 to mm hr-1.
-
-    Some precipitation diagnostics are output with unit kg m-2 s-1 and are converted to mm hr-1.
-    """
-    # if cube.attributes["STASH"] == "m01s04i203" or cube.long_name == "surface_microphysical_rainfall_rate":
-    if cube.long_name == "surface_microphysical_rainfall_rate":
-        if cube.units == "kg m-2 s-1":
-            logging.info("Converting precipitation units from kg m-2 s-1 to mm hr-1")
-            # manually convert from kg m-2 s-1 to mm hr-1 assuming 1kg water = 1l water = 1dm^3 water
-            cube.data = cube.data * 3600.0
-
-            # update the units
-            cube.units = "mm hr-1"
-        else:
-            logging.warning(
-                "Precipitation units are not in 'kg m-2 s-1', skipping conversion"
-            )
-    return cube

From 003ce0988fd429a47058d6295a49e24ac3bef559 Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Wed, 26 Mar 2025 16:51:43 +0000
Subject: [PATCH 09/13] new internal function for colorbar for microphysical
 precipitation

---
 src/CSET/operators/plot.py | 48 +++++++++++++++++++++++++++++++++++---
 1 file changed, 45 insertions(+), 3 deletions(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index e63aee68a..4b79a4d11 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -246,6 +246,11 @@ def _colorbar_map_levels(cube: iris.cube.Cube):
                 norm = mpl.colors.BoundaryNorm(levels, ncolors=cmap.N)
                 logging.debug("Using levels for %s colorbar.", varname)
                 logging.info("Using levels: %s", levels)
+                # Overwrite cmap, levels and norm for specific variables that require custom colorbar_map as these
+                # can not be defined in the json file.
+                cmap, levels, norm = _custom_colourmap_precipitation(
+                    cube, cmap, levels, norm
+                )
             except KeyError:
                 # Get the range for this variable.
                 vmin, vmax = var_colorbar["min"], var_colorbar["max"]
@@ -954,6 +959,46 @@ def _convert_precipitation_units_callback(cube: iris.cube.Cube):
     return cube
 
 
+def _custom_colourmap_precipitation(cube: iris.cube.Cube, cmap, levels, norm):
+    """Return a custom colourmap for the current recipe."""
+    import matplotlib.colors as mcolors
+
+    if (
+        cube.long_name == "surface_microphysical_rainfall_rate"
+        or cube.standard_name == "surface_microphysical_rainfall_rate"
+        or cube.var_name == "surface_microphysical_rainfall_rate"
+    ):
+        # Define the levels and colors
+        levels = [0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128]
+        colors = [
+            (0, 0, 0.6),
+            "b",
+            "c",
+            "g",
+            "y",
+            (1, 0.5, 0),
+            "r",
+            "m",
+            (0.6, 0.6, 0.6),
+            "k",
+        ]
+
+        # Create a custom colormap
+        cmap = mcolors.ListedColormap(colors)
+
+        # Normalize the levels
+        norm = mcolors.BoundaryNorm(levels, cmap.N)
+        logging.info(
+            "change colormap for surface_microphysical_rainfall_rate colorbar."
+        )
+    else:
+        # do nothing and keep existing colorbar attributes
+        cmap = cmap
+        levels = levels
+        norm = norm
+    return cmap, levels, norm
+
+
 ####################
 # Public functions #
 ####################
@@ -1049,9 +1094,6 @@ def spatial_pcolormesh_plot(
     TypeError
         If the cube isn't a single cube.
     """
-    # Convert precipitation units if necessary
-    _convert_precipitation_units_callback(cube)
-
     _spatial_plot("pcolormesh", cube, filename, sequence_coordinate, stamp_coordinate)
     return cube
 

From b0ee03daaaea1cc27936bade578e1fc27eacc125 Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Thu, 27 Mar 2025 15:05:42 +0000
Subject: [PATCH 10/13] remove vmin/vmax when norm is calculated for
 pcolormesh. this enables plotting of fields with level information such as
 precipitation instead of vmin/vmax information.

---
 src/CSET/operators/_colorbar_definition.json | 14 ++-----------
 src/CSET/operators/plot.py                   | 22 ++++++++++++--------
 2 files changed, 15 insertions(+), 21 deletions(-)

diff --git a/src/CSET/operators/_colorbar_definition.json b/src/CSET/operators/_colorbar_definition.json
index c06f7ac39..b899b7a60 100644
--- a/src/CSET/operators/_colorbar_definition.json
+++ b/src/CSET/operators/_colorbar_definition.json
@@ -392,18 +392,8 @@
   },
   "surface_microphysical_rainfall_rate": {
     "cmap": "cividis",
-    "levels": [
-      0.125,
-      0.25,
-      0.5,
-      1,
-      2,
-      4,
-      8,
-      16,
-      32,
-      64
-    ]
+    "max": 256.0,
+    "min": 0.0
   },
   "surface_microphysical_rainfall_rate_difference": {
     "cmap": "bwr",
diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 4b79a4d11..6af7ff92f 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -258,6 +258,9 @@ def _colorbar_map_levels(cube: iris.cube.Cube):
                 # Calculate levels from range.
                 levels = np.linspace(vmin, vmax, 51)
                 norm = None
+                cmap, levels, norm = _custom_colourmap_precipitation(
+                    cube, cmap, levels, norm
+                )
             return cmap, levels, norm
         except KeyError:
             logging.debug("Cube name %s has no colorbar definition.", varname)
@@ -305,13 +308,16 @@ def _plot_and_save_spatial_plot(
         # Filled contour plot of the field.
         plot = iplt.contourf(cube, cmap=cmap, levels=levels, norm=norm)
     elif method == "pcolormesh":
-        # try:
-        #    vmin = min(levels)
-        #    vmax = max(levels)
-        # except TypeError:
-        # vmin, vmax = None, None
-        # pcolormesh plot of the field.
-        plot = iplt.pcolormesh(cube, cmap=cmap, norm=norm)
+        try:
+            vmin = min(levels)
+            vmax = max(levels)
+        except TypeError:
+            vmin, vmax = None, None
+        # pcolormesh plot of the field and ensure not to use norm and not vmin/vmax if levels are defined.
+        if norm is not None:
+            vmin = None
+            vmax = None
+        plot = iplt.pcolormesh(cube, cmap=cmap, norm=norm, vmin=vmin, vmax=vmax)
     else:
         raise ValueError(f"Unknown plotting method: {method}")
 
@@ -982,10 +988,8 @@ def _custom_colourmap_precipitation(cube: iris.cube.Cube, cmap, levels, norm):
             (0.6, 0.6, 0.6),
             "k",
         ]
-
         # Create a custom colormap
         cmap = mcolors.ListedColormap(colors)
-
         # Normalize the levels
         norm = mcolors.BoundaryNorm(levels, cmap.N)
         logging.info(

From 4463e55bb82dc414706ee7d76341417c69234d7f Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Thu, 27 Mar 2025 15:20:46 +0000
Subject: [PATCH 11/13] change colourbar_map for precipitation and align with
 ukep_plot.

---
 src/CSET/operators/plot.py | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 6af7ff92f..5b7507549 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -975,8 +975,9 @@ def _custom_colourmap_precipitation(cube: iris.cube.Cube, cmap, levels, norm):
         or cube.var_name == "surface_microphysical_rainfall_rate"
     ):
         # Define the levels and colors
-        levels = [0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128]
+        levels = [0, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256]
         colors = [
+            "w",
             (0, 0, 0.6),
             "b",
             "c",
@@ -984,9 +985,11 @@ def _custom_colourmap_precipitation(cube: iris.cube.Cube, cmap, levels, norm):
             "y",
             (1, 0.5, 0),
             "r",
+            "pink",
             "m",
-            (0.6, 0.6, 0.6),
-            "k",
+            "purple",
+            "maroon",
+            "gray",
         ]
         # Create a custom colormap
         cmap = mcolors.ListedColormap(colors)

From 2d8c92321412cb1a6f94ef1cd7d5efdab06cdfa0 Mon Sep 17 00:00:00 2001
From: Sylviabohnenstengel <Sylvia.bohnenstengel@metoffice.gov.uk>
Date: Thu, 27 Mar 2025 17:28:36 +0000
Subject: [PATCH 12/13] enable a tick for each level if less than 20 levels and
 include levels into colourbar.json file.

---
 src/CSET/operators/_colorbar_definition.json | 17 +++++++++++++++--
 src/CSET/operators/plot.py                   |  6 +++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/CSET/operators/_colorbar_definition.json b/src/CSET/operators/_colorbar_definition.json
index b899b7a60..7f670e1ec 100644
--- a/src/CSET/operators/_colorbar_definition.json
+++ b/src/CSET/operators/_colorbar_definition.json
@@ -392,8 +392,21 @@
   },
   "surface_microphysical_rainfall_rate": {
     "cmap": "cividis",
-    "max": 256.0,
-    "min": 0.0
+    "levels": [
+      0,
+      0.125,
+      0.25,
+      0.5,
+      1,
+      2,
+      4,
+      8,
+      16,
+      32,
+      64,
+      128,
+      256
+    ]
   },
   "surface_microphysical_rainfall_rate_difference": {
     "cmap": "bwr",
diff --git a/src/CSET/operators/plot.py b/src/CSET/operators/plot.py
index 5b7507549..a63d26097 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -313,7 +313,7 @@ def _plot_and_save_spatial_plot(
             vmax = max(levels)
         except TypeError:
             vmin, vmax = None, None
-        # pcolormesh plot of the field and ensure not to use norm and not vmin/vmax if levels are defined.
+        # pcolormesh plot of the field and ensure to use norm and not vmin/vmax if levels are defined.
         if norm is not None:
             vmin = None
             vmax = None
@@ -384,6 +384,10 @@ def _plot_and_save_spatial_plot(
     # Add colour bar.
     cbar = fig.colorbar(plot)
     cbar.set_label(label=f"{cube.name()} ({cube.units})", size=20)
+    # add ticks and tick_labels for every levels if less than 20 levels exist
+    if levels is not None and len(levels) < 20:
+        cbar.set_ticks(levels)
+        cbar.set_ticklabels([f"{level:.1f}" for level in levels])
 
     # Save plot.
     fig.savefig(filename, bbox_inches="tight", dpi=_get_plot_resolution())

From 7d8dd9ab623ab6a1a5f1ef3502f26cc374562f17 Mon Sep 17 00:00:00 2001
From: Sylvia Bohnenstengel
 <62748926+Sylviabohnenstengel@users.noreply.github.com>
Date: Mon, 31 Mar 2025 09:30:13 +0100
Subject: [PATCH 13/13] Update src/CSET/operators/plot.py

Co-authored-by: James Frost <james.frost@metoffice.gov.uk>
---
 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 b611d361b..97049ae3d 100644
--- a/src/CSET/operators/plot.py
+++ b/src/CSET/operators/plot.py
@@ -959,11 +959,11 @@ def _convert_precipitation_units_callback(cube: iris.cube.Cube):
     if cube.long_name == "surface_microphysical_rainfall_rate":
         if cube.units == "kg m-2 s-1":
             logging.info("Converting precipitation units from kg m-2 s-1 to mm hr-1")
-            # manually convert from kg m-2 s-1 to mm hr-1 assuming 1kg water = 1l water = 1dm^3 water
-            cube.data = cube.data * 3600.0
-
-            # update the units
-            cube.units = "mm hr-1"
+            # Convert from kg m-2 s-1 to mm s-1 assuming 1kg water = 1l water = 1dm^3 water.
+            # This is a 1:1 conversion, so we just change the units.
+            cube.units = "mm s-1"
+            # Convert the units to per hour.
+            cube.convert_units("mm hr-1")
         else:
             logging.warning(
                 "Precipitation units are not in 'kg m-2 s-1', skipping conversion"