Errors reported by IOOS but not this tool

[mankoff]

The IOOS CF checker reports many errors on the NetCDF file at https://doi.org/10.48567/efwt-jw56 but this tool reports one error. The IOOS web checker times out, but when run locally I see,

cchecker.py -t cf:1.6 recon_t2m_1958-1960_ano.final.nc

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                     IOOS Compliance Checker Report                         
                             Version 5.1.1                                  
                 Report generated 2025-02-21T04:38:49Z                      
                                 cf:1.6                                     
   http://cfconventions.org/cf-conventions/v1.6.0/cf-conventions.html       

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                           Corrective Actions                               

recon_t2m_1958-1960_ano.final.nc has 5 potential issues

                                 Errors                                     

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§5.6 Horizontal Coordinate Reference Systems, Grid Mappings, Projections

• HGT has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of HGT's dimensions

• HGT has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of HGT's dimensions

• LANDMASK has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of LANDMASK's dimensions

• LANDMASK has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of LANDMASK's dimensions

• RECON has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of RECON's dimensions

• RECON has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of RECON's dimensions

• XLAT_M has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of XLAT_M's dimensions

• XLAT_M has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of XLAT_M's dimensions

• XLONG_M has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of XLONG_M's dimensions

• XLONG_M has no coordinate associated with a variable identified as true latitude/longitude; its coordinate variable should also share a subset of XLONG_M's dimensions

                                Warnings                                    
  

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§2.3 Naming Conventions

• global attribute WEST-EAST_GRID_DIMENSION should begin with a letter and be composed of letters, digits, and underscores
• global attribute SOUTH-NORTH_GRID_DIMENSION should begin with a letter and be composed of letters, digits, and underscores
• global attribute BOTTOM-TOP_GRID_DIMENSION should begin with a letter and be composed of letters, digits, and underscores
• global attribute WEST-EAST_PATCH_START_UNSTAG should begin with a letter and be composed of letters, digits, and underscores
• global attribute WEST-EAST_PATCH_END_UNSTAG should begin with a letter and be composed of letters, digits, and underscores
• global attribute WEST-EAST_PATCH_START_STAG should begin with a letter and be composed of letters, digits, and underscores
• global attribute WEST-EAST_PATCH_END_STAG should begin with a letter and be composed of letters, digits, and underscores
• global attribute SOUTH-NORTH_PATCH_START_UNSTAG should begin with a letter and be composed of letters, digits, and underscores
• global attribute SOUTH-NORTH_PATCH_END_UNSTAG should begin with a letter and be composed of letters, digits, and underscores
• global attribute SOUTH-NORTH_PATCH_START_STAG should begin with a letter and be composed of letters, digits, and underscores
• global attribute SOUTH-NORTH_PATCH_END_STAG should begin with a letter and be composed of letters, digits, and underscores

§2.6 Attributes

• §2.6.2 global attribute title should exist and be a non-empty string

§4.1 Latitude Coordinate

• latitude variable 'XLAT_M' should define standard_name='latitude' or axis='Y'
• latitude variable 'XLAT_C' should define standard_name='latitude' or axis='Y'

§4.2 Longitude Coordinate

• longitude variable 'XLONG_M' should define standard_name='longitude' or axis='X'
• longitude variable 'XLONG_C' should define standard_name='longitude' or axis='X'

While this tool (web interface at https://cfchecker.ncas.ac.uk/) reports only the following. Is there some reason for the difference in reports?

Uploaded File: recon_t2m_1958-1960_ano.final.nc

CHECKING NetCDF FILE: /tmp/tmpj6oa0l93.nc
=====================
Using CF Checker Version 4.1.0
Checking against CF Version CF-1.8
Using Standard Name Table Version 89 (2025-01-21T13:26:50Z)
Using Area Type Table Version 12 (21 January 2025)
Using Standardized Region Name Table Version 5 (12 November 2024)

WARN: (2.3): Global attribute WEST-EAST_GRID_DIMENSION: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute SOUTH-NORTH_GRID_DIMENSION: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute BOTTOM-TOP_GRID_DIMENSION: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute WEST-EAST_PATCH_START_UNSTAG: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute WEST-EAST_PATCH_END_UNSTAG: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute WEST-EAST_PATCH_START_STAG: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute WEST-EAST_PATCH_END_STAG: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute SOUTH-NORTH_PATCH_START_UNSTAG: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute SOUTH-NORTH_PATCH_END_UNSTAG: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute SOUTH-NORTH_PATCH_START_STAG: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.3): Global attribute SOUTH-NORTH_PATCH_END_STAG: Attribute names should begin with a letter and be composed of letters, digits and underscores
WARN: (2.6.1): Inconsistency - This netCDF file appears to contain CF-1.6 data, but you've requested a validity check against CF-1.8

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Checking variable: time
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Checking variable: RECON
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Checking variable: XLAT
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Checking variable: XLONG
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Checking variable: HGT
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Checking variable: LANDMASK
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ERROR: (3.1): Invalid units: (0 - 1)

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Checking variable: XLAT_M
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Checking variable: XLONG_M
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Checking variable: XLAT_C
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Checking variable: XLONG_C
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ERRORS detected: 1
WARNINGS given: 12
INFORMATION messages: 0

[RosalynHatcher]

Hi,

The CF Checker checks against the list of requirements and recommendations listed in the CF Conformance document here: https://cfconventions.org/Data/cf-documents/requirements-recommendations/requirements-recommendations-1.6.html. The requirement regarding true latitude/longitude is not listed here and that is why this CF Checker doesn't complain.

I will take a look and get the conformance document updated as appropriate and then the fix will be applied to the CF Checker.

Thanks for raising this.
Regards,
Ros