CF Compliance

NetCDF attribute conventions and encoding.

All NetCDF outputs follow CF Conventions 1.8, so the files are readable by CDO, NCO, xarray, netCDF4, GDAL, and any other CF-aware tool without custom handling.

Encoding

netcdf_encoding:
  precipitation:
    dtype: "float32"
    zlib: true
    complevel: 4
    _FillValue: .nan

float32 keeps file size manageable (half of float64) without losing meaningful precision for precipitation in mm.
zlib compression gives typically 3-5x reduction on precipitation fields.
NaN is the fill value for ocean and outside-AOI cells. This is more portable than -9999 and works directly with xarray’s masked operations.

Required CF attributes

Every output NetCDF carries:

Variable / Global	Attribute	Example
`precipitation`	`standard_name`	`lwe_precipitation_rate`
`precipitation`	`long_name`	`Bias-corrected daily precipitation`
`precipitation`	`units`	`mm day-1`
`precipitation`	`_FillValue`	`NaN`
`lat`	`standard_name`	`latitude`
`lat`	`units`	`degrees_north`
`lon`	`standard_name`	`longitude`
`lon`	`units`	`degrees_east`
`time`	`standard_name`	`time`
`time`	`units`	`days since 2001-01-01`
Global	`Conventions`	`CF-1.8`
Global	`title`	`Hybrid Bias Correction - LSEQM+DL`
Global	`source`	`IMERG Late Run V07 corrected with CPC-UNI`
Global	`history`	timestamped processing record
Global	`references`	Zenodo dataset DOI (and manuscript DOI once available)
Global	`method`	one of `ls`, `lseqm`, `lseqmdl`

Reproducibility metadata

Each output NetCDF also carries non-CF attributes recording the run context:

framework_version - DateVer tag (e.g. v2026.05)
git_commit - short SHA of the source revision
config_file - path to the config used
run_timestamp - ISO 8601, UTC
blend_alpha, gpd_threshold_percentile, saturation_count - the three sensitivity parameters

These are not required by CF but make a downstream user’s life much easier when comparing files produced months apart.

How to inspect

ncdump -h <file>.nc4         # full header
xr.open_dataset(<file>).attrs # all globals

Or browse interactively in Panoply for a quick visual.

--- title: "CF Compliance" description: "NetCDF attribute conventions and encoding." --- All NetCDF outputs follow [CF Conventions 1.8](https://cfconventions.org/Data/cf-conventions/cf-conventions-1.8/cf-conventions.html), so the files are readable by CDO, NCO, xarray, netCDF4, GDAL, and any other CF-aware tool without custom handling. ## Encoding ```yaml netcdf_encoding: precipitation: dtype: "float32" zlib: true complevel: 4 _FillValue: .nan ``` - `float32` keeps file size manageable (half of `float64`) without losing meaningful precision for precipitation in mm. - `zlib` compression gives typically 3-5x reduction on precipitation fields. - `NaN` is the fill value for ocean and outside-AOI cells. This is more portable than `-9999` and works directly with xarray's masked operations. ## Required CF attributes Every output NetCDF carries: | Variable / Global | Attribute | Example | |-------------------|-----------|---------| | `precipitation` | `standard_name` | `lwe_precipitation_rate` | | `precipitation` | `long_name` | `Bias-corrected daily precipitation` | | `precipitation` | `units` | `mm day-1` | | `precipitation` | `_FillValue` | `NaN` | | `lat` | `standard_name` | `latitude` | | `lat` | `units` | `degrees_north` | | `lon` | `standard_name` | `longitude` | | `lon` | `units` | `degrees_east` | | `time` | `standard_name` | `time` | | `time` | `units` | `days since 2001-01-01` | | Global | `Conventions` | `CF-1.8` | | Global | `title` | `Hybrid Bias Correction - LSEQM+DL` | | Global | `source` | `IMERG Late Run V07 corrected with CPC-UNI` | | Global | `history` | timestamped processing record | | Global | `references` | Zenodo dataset DOI (and manuscript DOI once available) | | Global | `method` | one of `ls`, `lseqm`, `lseqmdl` | ## Reproducibility metadata Each output NetCDF also carries non-CF attributes recording the run context: - `framework_version` - DateVer tag (e.g. `v2026.05`) - `git_commit` - short SHA of the source revision - `config_file` - path to the config used - `run_timestamp` - ISO 8601, UTC - `blend_alpha`, `gpd_threshold_percentile`, `saturation_count` - the three sensitivity parameters These are not required by CF but make a downstream user's life much easier when comparing files produced months apart. ## How to inspect ```bash ncdump -h <file>.nc4 # full header xr.open_dataset(<file>).attrs # all globals ``` Or browse interactively in [Panoply](https://www.giss.nasa.gov/tools/panoply/) for a quick visual.