Comments (2)
If I understand right, what this represents is a cloud fractional coverage, for all the atmosphere between ground level and the 800 hPa level.
So I think this is a problem from Iris' point of view, because Iris data-model is all aligned with netcdf-CF rules, and CF just does not provide a means of describing what is intended here.
In CF terms this information "should" translate into a one-point vertical coordinate with a point value and bounds. However, CF expects upper and lower bound values to have common units and meaning, whereas here the correct upper bound is a pressure value, but the lower bound (ground level) can not be given as a (fixed) pressure.
So the key problem is how should this data appear in Iris ?
I can think of a few possibilities :
- use a nominal fixed pressure value for the lower surface, e.g. 1000 hPa (standard) or 100e6 (improbably large); .. or ..
- .. define a new (Iris-specific) nonstandard phenomenon identity meaning 'cloud below given level', and load with a pressure point-value only (no bounds or equal-value bounds)
- and (optionally) add case-specific metadata to track metadata adjustments
Such solutions can be potentially be implemented by extending iris-grib. However, a user-code-specific solution is obviously more flexible as you don't need to resolve the core problem in a generally acceptable way.
You can modify low-level data before translating, with a callback function or via iris_grib.load_pairs_from_fields
(see docs).
It really depends on what you then need to do with the data.
If you just needs a means of loading (working around the load error), I think I would just set the type and value of the second fixed surface to that of the first in this case, using a load callback.
That will yield a cube that apparently has a specific cloud fraction value between levels of 800 to 800 hPa, which is nonsensical but at least no original information is lost.
What kind of solution do you need ?
from iris-grib.
Just wanted to note that I just ran into the exact same problem. For me, it would be enough to change the second fixed surface to look like the first, as you suggested. How would such a callback look like?
from iris-grib.
Related Issues (20)
- Support for template 5.42 with compression HOT 1
- iris-grib choking on zero arrays HOT 4
- Unable to import iris_grib HOT 4
- Fix iris-grib doctests (in cirrus) HOT 1
- Not saving first dimension as grib and renaming sea_water_y_velocity to sea_water_x_velocity HOT 7
- Reenable code coverage testing
- Testing against Iris release and Iris master branch HOT 1
- Rename master to main HOT 2
- 0.17.1 on PyPI? HOT 2
- Add github action to auto publish to PyPI HOT 1
- Incorrectly loaded grib file on Windows HOT 10
- Incorrect coding of x_start/y_start for space view grid definition HOT 3
- Inaccurate method for calculating GRIB1 coordinates HOT 2
- iris.exceptions.TranslationError: grib statistic time-increment type [3] is not supported. HOT 2
- Add support for Fixed surface type 108 HOT 1
- Replace nox with tox
- Incorrect translation of forecastTimeUnits for values other than "hours" on bounded forecast_period coordinates HOT 2
- No documentation of GRIB_PARAM
- Grid definition template 32769 is not supported HOT 5
- Loading grib 1 doesn't create realization dimension HOT 3
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from iris-grib.