contourf only drawing one level

[rcomer]

Description

This is an Iris-free reproducer of #1076 (comment). Note that Iris has its own automatic equivalent of add_cyclic, which is required to reproduce the problem.

Code to reproduce

(the data file temp.nc is in the attached temp.zip)

import numpy as np
import matplotlib.pyplot as plt
from xarray import open_dataset

import cartopy.util
import cartopy.crs as ccrs

ds = open_dataset('temp.nc')
da = ds.air_pressure_at_sea_level

mslp, lon, lat = cartopy.util.add_cyclic(da.data, da.longitude, da.latitude)

proj = ccrs.Orthographic(central_longitude=0.0, central_latitude=90.0)

def plot_mslp(n_levels):
    ax=plt.axes(projection=proj)
    ax.contourf(lon, lat, mslp, levels=np.linspace(-9, 0, n_levels), transform=ccrs.PlateCarree())
    ax.coastlines()
    plt.show()

for n_levels in [10, 11]:
    plot_mslp(n_levels)

Actual Output

Expected Output

Without the call to add_cyclic, we get

Full environment definition

Operating system

Ubuntu

Cartopy version

main, v0.24

conda list

# packages in environment at /home/ruth/miniforge3/envs/cartopy-dev:
#
# Name                    Version                   Build  Channel
_libgcc_mutex             0.1                 conda_forge    conda-forge
_openmp_mutex             4.5                       2_gnu    conda-forge
accessible-pygments       0.0.5              pyhd8ed1ab_0    conda-forge
alabaster                 1.0.0              pyhd8ed1ab_0    conda-forge
asttokens                 2.4.1              pyhd8ed1ab_0    conda-forge
babel                     2.14.0             pyhd8ed1ab_0    conda-forge
beautifulsoup4            4.12.3             pyha770c72_0    conda-forge
blosc                     1.21.6               hef167b5_0    conda-forge
brotli                    1.1.0                hb9d3cd8_2    conda-forge
brotli-bin                1.1.0                hb9d3cd8_2    conda-forge
brotli-python             1.1.0           py312h2ec8cdc_2    conda-forge
bzip2                     1.0.8                h4bc722e_7    conda-forge
c-ares                    1.33.1               heb4867d_0    conda-forge
ca-certificates           2024.8.30            hbcca054_0    conda-forge
cartopy                   0.24.2.dev30+gd8e8bdf9          pypi_0    pypi
certifi                   2024.8.30          pyhd8ed1ab_0    conda-forge
cffi                      1.17.1          py312h06ac9bb_0    conda-forge
cfgv                      3.3.1              pyhd8ed1ab_0    conda-forge
cftime                    1.6.4           py312hc0a28a1_1    conda-forge
charset-normalizer        3.3.2              pyhd8ed1ab_0    conda-forge
colorama                  0.4.6              pyhd8ed1ab_0    conda-forge
contourpy                 1.3.0           py312h68727a3_2    conda-forge
cycler                    0.12.1             pyhd8ed1ab_0    conda-forge
cython                    3.0.11          py312h8fd2918_3    conda-forge
dataclasses               0.8                pyhc8e2a94_3    conda-forge
decorator                 5.1.1              pyhd8ed1ab_0    conda-forge
distlib                   0.3.8              pyhd8ed1ab_0    conda-forge
docutils                  0.21.2             pyhd8ed1ab_0    conda-forge
exceptiongroup            1.2.2              pyhd8ed1ab_0    conda-forge
execnet                   2.1.1              pyhd8ed1ab_0    conda-forge
executing                 2.1.0              pyhd8ed1ab_0    conda-forge
filelock                  3.16.1             pyhd8ed1ab_0    conda-forge
fonttools                 4.54.1          py312h66e93f0_0    conda-forge
freetype                  2.12.1               h267a509_2    conda-forge
geos                      3.13.0               h5888daf_0    conda-forge
h2                        4.1.0              pyhd8ed1ab_0    conda-forge
hdf4                      4.2.15               h2a13503_7    conda-forge
hdf5                      1.14.4          nompi_h2d575fe_101    conda-forge
hpack                     4.0.0              pyh9f0ad1d_0    conda-forge
hyperframe                6.0.1              pyhd8ed1ab_0    conda-forge
icu                       75.1                 he02047a_0    conda-forge
identify                  2.6.1              pyhd8ed1ab_0    conda-forge
idna                      3.10               pyhd8ed1ab_0    conda-forge
imagesize                 1.4.1              pyhd8ed1ab_0    conda-forge
importlib_resources       6.4.5              pyhd8ed1ab_0    conda-forge
iniconfig                 2.0.0              pyhd8ed1ab_0    conda-forge
ipython                   8.28.0             pyh707e725_0    conda-forge
jedi                      0.19.1             pyhd8ed1ab_0    conda-forge
jinja2                    3.1.4              pyhd8ed1ab_0    conda-forge
keyutils                  1.6.1                h166bdaf_0    conda-forge
kiwisolver                1.4.7           py312h68727a3_0    conda-forge
krb5                      1.21.3               h659f571_0    conda-forge
lcms2                     2.16                 hb7c19ff_0    conda-forge
ld_impl_linux-64          2.43                 h712a8e2_1    conda-forge
lerc                      4.0.0                h27087fc_0    conda-forge
libaec                    1.1.3                h59595ed_0    conda-forge
libblas                   3.9.0           24_linux64_openblas    conda-forge
libbrotlicommon           1.1.0                hb9d3cd8_2    conda-forge
libbrotlidec              1.1.0                hb9d3cd8_2    conda-forge
libbrotlienc              1.1.0                hb9d3cd8_2    conda-forge
libcblas                  3.9.0           24_linux64_openblas    conda-forge
libcurl                   8.10.1               hbbe4b11_0    conda-forge
libdeflate                1.21                 h4bc722e_0    conda-forge
libedit                   3.1.20191231         he28a2e2_2    conda-forge
libev                     4.33                 hd590300_2    conda-forge
libexpat                  2.6.3                h5888daf_0    conda-forge
libffi                    3.4.2                h7f98852_5    conda-forge
libgcc                    14.1.0               h77fa898_1    conda-forge
libgcc-ng                 14.1.0               h69a702a_1    conda-forge
libgfortran               14.1.0               h69a702a_1    conda-forge
libgfortran-ng            14.1.0               h69a702a_1    conda-forge
libgfortran5              14.1.0               hc5f4f2c_1    conda-forge
libgomp                   14.1.0               h77fa898_1    conda-forge
libiconv                  1.17                 hd590300_2    conda-forge
libjpeg-turbo             3.0.0                hd590300_1    conda-forge
liblapack                 3.9.0           24_linux64_openblas    conda-forge
libnetcdf                 4.9.2           nompi_h2564987_115    conda-forge
libnghttp2                1.58.0               h47da74e_1    conda-forge
libnsl                    2.0.1                hd590300_0    conda-forge
libopenblas               0.3.27          pthreads_hac2b453_1    conda-forge
libpng                    1.6.44               hadc24fc_0    conda-forge
libsqlite                 3.46.1               hadc24fc_0    conda-forge
libssh2                   1.11.0               h0841786_0    conda-forge
libstdcxx                 14.1.0               hc0a3c3a_1    conda-forge
libstdcxx-ng              14.1.0               h4852527_1    conda-forge
libtiff                   4.7.0                h6565414_0    conda-forge
libuuid                   2.38.1               h0b41bf4_0    conda-forge
libwebp-base              1.4.0                hd590300_0    conda-forge
libxcb                    1.17.0               h8a09558_0    conda-forge
libxcrypt                 4.4.36               hd590300_1    conda-forge
libxml2                   2.12.7               he7c6b58_4    conda-forge
libxslt                   1.1.39               h76b75d6_0    conda-forge
libzip                    1.11.1               hf83b1b0_0    conda-forge
libzlib                   1.3.1                hb9d3cd8_2    conda-forge
lxml                      5.3.0           py312he28fd5a_1    conda-forge
lz4-c                     1.9.4                hcb278e6_0    conda-forge
markupsafe                2.1.5           py312h66e93f0_1    conda-forge
matplotlib-base           3.9.2           py312he9b69db_201    conda-forge/label/testing
matplotlib-inline         0.1.7              pyhd8ed1ab_0    conda-forge
munkres                   1.1.4              pyh9f0ad1d_0    conda-forge
ncurses                   6.5                  he02047a_1    conda-forge
netcdf4                   1.7.1           nompi_py312ha728dd9_103    conda-forge
nodeenv                   1.9.1              pyhd8ed1ab_0    conda-forge
numpy                     2.1.1           py312h58c1407_0    conda-forge
openjpeg                  2.5.2                h488ebb8_0    conda-forge
openssl                   3.3.2                hb9d3cd8_0    conda-forge
owslib                    0.31.0             pyhd8ed1ab_0    conda-forge
packaging                 24.1               pyhd8ed1ab_0    conda-forge
pandas                    2.2.2           py312h1d6d2e6_1    conda-forge
parso                     0.8.4              pyhd8ed1ab_0    conda-forge
pexpect                   4.9.0              pyhd8ed1ab_0    conda-forge
pickleshare               0.7.5                   py_1003    conda-forge
pillow                    10.4.0          py312h56024de_1    conda-forge
pip                       24.2               pyh8b19718_1    conda-forge
platformdirs              4.3.6              pyhd8ed1ab_0    conda-forge
pluggy                    1.5.0              pyhd8ed1ab_0    conda-forge
pre-commit                4.0.0              pyha770c72_0    conda-forge
proj                      9.5.0                h12925eb_0    conda-forge
prompt-toolkit            3.0.48             pyha770c72_0    conda-forge
pthread-stubs             0.4               hb9d3cd8_1002    conda-forge
ptyprocess                0.7.0              pyhd3deb0d_0    conda-forge
pure_eval                 0.2.3              pyhd8ed1ab_0    conda-forge
pycparser                 2.22               pyhd8ed1ab_0    conda-forge
pydata-sphinx-theme       0.15.4             pyhd8ed1ab_0    conda-forge
pygments                  2.18.0             pyhd8ed1ab_0    conda-forge
pykdtree                  1.3.13          py312hc0a28a1_1    conda-forge
pyparsing                 3.1.4              pyhd8ed1ab_0    conda-forge
pyproj                    3.7.0           py312he630544_0    conda-forge
pyshp                     2.3.1              pyhd8ed1ab_0    conda-forge
pysocks                   1.7.1              pyha2e5f31_6    conda-forge
pytest                    8.3.3              pyhd8ed1ab_0    conda-forge
pytest-mpl                0.17.0             pyhd8ed1ab_0    conda-forge
pytest-xdist              3.6.1              pyhd8ed1ab_0    conda-forge
python                    3.12.7          hc5c86c4_0_cpython    conda-forge
python-dateutil           2.9.0              pyhd8ed1ab_0    conda-forge
python-tzdata             2024.2             pyhd8ed1ab_0    conda-forge
python_abi                3.12                    5_cp312    conda-forge
pytz                      2024.2             pyhd8ed1ab_0    conda-forge
pyyaml                    6.0.2           py312h66e93f0_1    conda-forge
qhull                     2020.2               h434a139_5    conda-forge
readline                  8.2                  h8228510_1    conda-forge
requests                  2.32.3             pyhd8ed1ab_0    conda-forge
ruff                      0.6.9           py312hd18ad41_0    conda-forge
scipy                     1.14.1          py312h7d485d2_0    conda-forge
setuptools                75.1.0             pyhd8ed1ab_0    conda-forge
setuptools-scm            8.1.0              pyhd8ed1ab_0    conda-forge
setuptools_scm            8.1.0                hd8ed1ab_0    conda-forge
shapely                   2.0.6           py312h391bc85_2    conda-forge
six                       1.16.0             pyh6c4a22f_0    conda-forge
snappy                    1.2.1                ha2e4443_0    conda-forge
snowballstemmer           2.2.0              pyhd8ed1ab_0    conda-forge
soupsieve                 2.5                pyhd8ed1ab_1    conda-forge
sphinx                    8.0.2              pyhd8ed1ab_0    conda-forge
sphinx-gallery            0.17.1             pyhd8ed1ab_0    conda-forge
sphinxcontrib-applehelp   2.0.0              pyhd8ed1ab_0    conda-forge
sphinxcontrib-devhelp     2.0.0              pyhd8ed1ab_0    conda-forge
sphinxcontrib-htmlhelp    2.1.0              pyhd8ed1ab_0    conda-forge
sphinxcontrib-jsmath      1.0.1              pyhd8ed1ab_0    conda-forge
sphinxcontrib-qthelp      2.0.0              pyhd8ed1ab_0    conda-forge
sphinxcontrib-serializinghtml 1.1.10             pyhd8ed1ab_0    conda-forge
sqlite                    3.46.1               h9eae976_0    conda-forge
stack_data                0.6.2              pyhd8ed1ab_0    conda-forge
tk                        8.6.13          noxft_h4845f30_101    conda-forge
tomli                     2.0.2              pyhd8ed1ab_0    conda-forge
traitlets                 5.14.3             pyhd8ed1ab_0    conda-forge
typing-extensions         4.12.2               hd8ed1ab_0    conda-forge
typing_extensions         4.12.2             pyha770c72_0    conda-forge
tzdata                    2024b                hc8b5060_0    conda-forge
ukkonen                   1.0.1           py312h68727a3_5    conda-forge
urllib3                   2.2.3              pyhd8ed1ab_0    conda-forge
virtualenv                20.26.6            pyhd8ed1ab_0    conda-forge
wcwidth                   0.2.13             pyhd8ed1ab_0    conda-forge
wheel                     0.44.0             pyhd8ed1ab_0    conda-forge
xarray                    2024.9.0           pyhd8ed1ab_0    conda-forge
xorg-libxau               1.0.11               hb9d3cd8_1    conda-forge
xorg-libxdmcp             1.1.5                hb9d3cd8_0    conda-forge
xz                        5.2.6                h166bdaf_0    conda-forge
yaml                      0.2.5                h7f98852_2    conda-forge
zipp                      3.20.2             pyhd8ed1ab_0    conda-forge
zlib                      1.3.1                hb9d3cd8_2    conda-forge
zstandard                 0.23.0          py312hef9b889_1    conda-forge
zstd                      1.5.6                ha6fb4c9_0    conda-forge