extract_levels preprocessor realizes source levels #2114
Description
The extract_levels preprocessor preprocessor function realizes the source levels. These can be as big as the data for cubes with a hybrid sigma coordinate. Example with a 15GB file where this becomes problematic:
from esmvalcore.dataset import Dataset
from esmvalcore.preprocessor import extract_levels
ds = Dataset(
short_name='clw',
mip='Amon',
project='CMIP6',
dataset='CESM2-WACCM',
exp='historical',
ensemble='r1i1p1f1',
grid='gn',
timerange='1850/2014',
)
cube = ds.load()
result = extract_levels(
cube,
levels=[0, 100000],
scheme='linear',
coordinate='air_pressure',
)