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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"TIPMIP Raw Data Units Are Inconsistent With ACCESS-ESM1_6 Mapping Assumptions","articleBody":"## Describe the issue\n\nFollowing a report from Laurie regarding unexpected units in several CMORised TIPMIP biogeochemical variables, we investigated the issue and identified the root cause.\n\nThe core issue is that the raw data units in the TIPMIP dataset are different from those in the ACCESS-ESM1_6 raw data that our current mappings and unit conversions were originally designed and tested against.\n\nAs a result, the CMORisation workflow applies incorrect assumptions about the source units when processing TIPMIP data, leading to mismatches between the CMORised data values and their reported units.\n\n---\n\n## Variables affected\n\n### 3D biogeochemical variables\n\nThe following variables are affected:\n\n- `o2`\n- `no3`\n- `dic`\n- `alk`\n\nCurrent mapping assumptions:\n\n| Variable | ACCESS-ESM1_6 raw data units | TIPMIP raw data units |\n|---|---|---|\n| o2 | mol/kg | mmol/m^3 |\n| no3 | mol/kg | mmol/m^3 |\n| dic | mol/kg | mmol/m^3 |\n| alk | mol/kg | mmol/m^3 |\n\nThe current mappings and unit conversion logic were implemented assuming the ACCESS-ESM1_6 raw data convention (`mol/kg`), which is not valid for TIPMIP raw data (`mmol/m^3`).\n\nThis causes the CMORised TIPMIP outputs to contain incorrect numerical values relative to the reported CMIP units.\n\n---\n\n### Productivity variable\n\n| Variable | ACCESS-ESM1_6 raw data units | TIPMIP raw data units |\n|---|---|---|\n| pprod_gross_2d | mol m-2 s-1 | mmolN/m^2/s |\n\nSimilarly, the mapping for `pprod_gross_2d` assumes the ACCESS-ESM1_6 convention and therefore does not correctly convert the TIPMIP source data units.\n\n---\n\n## Potential solution\n\nPossible approaches include:\n\n1. Add dataset-specific unit handling logic for TIPMIP\n2. Introduce explicit source-unit validation before CMORisation\n3. Implement automatic unit conversion based on detected raw-data units\n4. Separate mappings/configurations for ACCESS-ESM1_6 and TIPMIP datasets\n\n---\n\n## Additional context\n\nExamples reported by Laurie:\n- `o2` values appear to require division by `1000`\n- `dic`, `alk`, and `no3` also show inconsistent magnitudes\n- `pprod_gross_2d` metadata does not match source data units\n\nThis issue may affect additional biogeochemical variables and requires a broader audit of TIPMIP unit conventions.","author":{"url":"https://github.com/rhaegar325","@type":"Person","name":"rhaegar325"},"datePublished":"2026-05-25T04:27:53.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/395/ACCESS-MOPPy/issues/395"}