Wet bulb freezing level (#1949)

* Updates ExtractPressureLevel to also be able to extract a height level and updates unit tests

* Update plugin to use stratify's extrapolation

* Adds acceptance tests and cli for wet bulb freezing level. ALlso rename unit test file name.

* Updates to hail size plugin

* Formatting

* Update checksums and uncommenting

* update docstring formatting

* doc string updated

* review response

* formatting review changes

---------

Co-authored-by: Marcus Spelman <[email protected]>

improver/cli/wet_bulb_freezing_level.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# -----------------------------------------------------------------------------
+# (C) British Crown copyright. The Met Office.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice, this
+#   list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+#
+# * Neither the name of the copyright holder nor the names of its
+#   contributors may be used to endorse or promote products derived from
+#   this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+"""CLI to extract wet-bulb freezing level from wet-bulb temperature on height levels"""
+
+from improver import cli
+
+
+@cli.clizefy
+@cli.with_output
+def process(wet_bulb_temperature: cli.inputcube):
+    """Module to generate wet-bulb freezing level.
+
+    The height level at which the wet-bulb temperature first drops below 273.15K
+    (0 degrees Celsius) is extracted from the wet-bulb temperature cube starting from
+    the ground and ascending through height levels.
+
+    In grid squares where the temperature never goes below 273.15K the highest
+    height level on the cube is returned. In grid squares where the temperature
+    starts below 273.15K the lowest height on the cube is returned.
+
+    Args:
+        wet_bulb_temperature (iris.cube.Cube):
+            Cube of wet-bulb air temperatures over multiple height levels.
+
+    Returns:
+        iris.cube.Cube:
+            Cube of wet-bulb freezing level.
+
+    """
+    from improver.utilities.cube_extraction import ExtractLevel
+
+    wet_bulb_freezing_level = ExtractLevel(
+        positive_correlation=False, value_of_level=273.15
+    )(wet_bulb_temperature)
+    wet_bulb_freezing_level.rename("wet_bulb_freezing_level")
+
+    return wet_bulb_freezing_level

improver/psychrometric_calculations/hail_size.py

@@ -48,7 +48,7 @@
     saturated_humidity,
 )
 from improver.utilities.cube_checker import assert_spatial_coords_match
-from improver.utilities.cube_extraction import ExtractPressureLevel
+from improver.utilities.cube_extraction import ExtractLevel
 from improver.utilities.cube_manipulation import enforce_coordinate_ordering
 
 
@@ -525,18 +525,16 @@ def process(
             wet_bulb_zero_height_asl,
             orography,
         )
-        extract_pressure = ExtractPressureLevel(
-            value_of_pressure_level=268.15, positive_correlation=True
+        extract_pressure = ExtractLevel(
+            value_of_level=268.15, positive_correlation=True
         )
         pressure_at_268 = extract_pressure(temperature_on_pressure)
 
         temperature_at_268 = next(temperature_on_pressure.slices_over(["pressure"]))
         temperature_at_268.rename("temperature_of_atmosphere_at_268.15K")
         temperature_at_268.remove_coord("pressure")
         temperature = np.full_like(
-            temperature_at_268.data,
-            extract_pressure.value_of_pressure_level,
-            dtype=np.float32,
+            temperature_at_268.data, extract_pressure.value_of_level, dtype=np.float32,
         )
         temperature = np.ma.masked_where(np.ma.getmask(pressure_at_268), temperature)
         temperature_at_268.data = temperature