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Update ice_area to handle NaNs #237

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Merged
pgierz merged 3 commits into from
May 12, 2026
Merged

Update ice_area to handle NaNs #237

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bfb95b0
update ice_area to handle NaNs
Mukulikaa May 11, 2026
f10f759
Drop stray debug comment and trailing whitespace in ice_area
pgierz May 12, 2026
b908b0d
change default threshold and fix spelling
Mukulikaa May 12, 2026
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30 changes: 21 additions & 9 deletions pyfesom2/diagnostics.py
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ def add_timedim(data, date="1970-01-01"):
return data


def ice_ext(data, mesh, hemisphere="N", threshhold=0.15, attrs={}):
def ice_ext(data, mesh, hemisphere="N", threshold=0.15, attrs={}):
""" Compute sea ice extent.

Parameters
Expand All @@ -50,7 +50,7 @@ def ice_ext(data, mesh, hemisphere="N", threshhold=0.15, attrs={}):
FESOM2 mesh object.
hemisphere: str
can be ether 'N' or 'S'
threshhold: float
threshold: float
default is 0.15
attrs: dict
dictionary of attributes that will be put in the resulting
Expand All @@ -74,7 +74,7 @@ def ice_ext(data, mesh, hemisphere="N", threshhold=0.15, attrs={}):

if isinstance(data, xr.DataArray):
# Create binary ice extent field: 1 where ice >= threshold, 0 where < threshold, NaN stays NaN
ice_binary = xr.where(data >= threshhold, 1, 0)
ice_binary = xr.where(data >= threshold, 1, 0)
ice_binary = ice_binary.where(~np.isnan(data)) # Preserve NaN values (land)

finite_mask = ~np.isnan(ice_binary.squeeze().values)
Expand All @@ -88,7 +88,7 @@ def ice_ext(data, mesh, hemisphere="N", threshhold=0.15, attrs={}):
else:
logger.debug(data)
# Create binary ice extent field: 1 where ice >= threshold, 0 where < threshold, NaN stays NaN
ice_binary = np.where(data >= threshhold, 1, 0).astype(float)
ice_binary = np.where(data >= threshold, 1, 0).astype(float)
ice_binary[np.isnan(data)] = np.nan # Preserve NaN values (land)

finite_mask = ~np.isnan(ice_binary.squeeze())
Expand Down Expand Up @@ -140,8 +140,8 @@ def ice_vol(data, mesh, hemisphere="N", attrs={}):
return vol


def ice_area(data, mesh, hemisphere="N", attrs={}):
""" Compute sea ice volume.
def ice_area(data, mesh, hemisphere="N", threshold=0., attrs={}):
""" Compute sea ice area.
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@koldunovn koldunovn May 12, 2026

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I am not sure it's a good idea to put threshhold=0.15 - this is something we use for ice_extent, but definition of the area it the total area covered by sea ice, and at leas in my mind this is what I would want to see by default. Adding threshold is totally fine, but I would put 0 as a default.


Parameters
----------
Expand Down Expand Up @@ -175,13 +175,25 @@ def ice_area(data, mesh, hemisphere="N", attrs={}):
hemis_mask = mesh.y2 < 0

if isinstance(data, xr.DataArray):
vol = (data[:, hemis_mask] * mesh.lump2[hemis_mask]).sum(axis=1)
# Create ice area field: data where ice >= threshold, 0 where < threshold, NaN stays NaN
ice_field = xr.where(data >= threshold, data, 0)
ice_field = ice_field.where(~np.isnan(data)) # Preserve NaN values (land)

finite_mask = ~np.isnan(ice_field.squeeze().values)

area = (ice_field[:, hemis_mask & finite_mask] * mesh.lump2[hemis_mask & finite_mask]).sum(axis=1)
da = xr.DataArray(
vol, dims=["time"], coords={"time": data.time}, name=varname, attrs=attrs
area, dims=["time"], coords={"time": data.time}, name=varname, attrs=attrs
)
return da

else:
area = (data[:, hemis_mask] * mesh.lump2[hemis_mask]).sum(axis=1)
# Create ice area field: data where ice >= threshold, 0 where < threshold, NaN stays NaN
ice_field = np.where(data >= threshold, data, 0).astype(float)
ice_field[np.isnan(data)] = np.nan # Preserve NaN values (land)

finite_mask = ~np.isnan(ice_field.squeeze())
area = (ice_field[:, hemis_mask & finite_mask] * mesh.lump2[hemis_mask & finite_mask]).sum(axis=1)
return area


Expand Down
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