# Decisions

Open decisions and a dated log of decided ones for the pipeline and the
filter-by-filter review. The findings that led to them are in
[reviews/](reviews/); the plan they serve is [pipeline-plan.md](pipeline-plan.md).

## Open decisions

| Decision | Options | Needed by |
| --- | --- | --- |
| Committing large intermediates | Commit metric files only, or also source summaries | Phase 3 |
| Alaska and Hawaii coverage | Leave blank with a stated coverage gap, or add a source that covers them (for example Daymet or TerraClimate). NOAA nClimGrid and gridMET cover the contiguous U.S. only, so 29 AK and 5 HI counties are blank in filters 2–10; see finding 12 in [reviews/00-cross-filter.md](reviews/00-cross-filter.md) | Before Phase 3 |

## Decided

- **Köppen audit columns (2026-09-12):** `koppen.csv` stores the top class and
  share and the runner-up class and share alongside `koppenZone`.
- **Köppen no-data fallback (2026-09-12):** a county with no valid raster cells
  is left blank, not assigned `Cfa`.
- **Applying Köppen to the app CSV (2026-09-12):** wait until the app supports
  the Mixed class. Done 2026-09-13.
- **Metric files (2026-09-13):** one CSV per metric under `data/metrics/`,
  starting with `koppen.csv`.
- **Mixed climate display (2026-09-13):** diagonal stripes of each Mixed
  county's top two classes; see
  [koppen-mixed-display-plan.md](koppen-mixed-display-plan.md).
- **Puerto Rico (2026-09-13):** off the map and out of every filter. The app
  already drops state FIPS 72; the data files keep the rows.
- **Shared helpers (2026-09-13):** `scripts/common/` holds only code used by
  more than one data source, one topic per module; code shared within one data
  source stays with that source. Duplicates move during their own filter's
  review.
- **Annual avg temperature month weighting (2026-09-15):** the annual value is
  the equally weighted mean of the 12 monthly normals, not weighted by month
  length. This follows WMO-No. 1203 (2017) §4.3.3(a), whose footnote
  recommends against day-length weighting, and NOAA's 1991–2020 Normals
  methodology (p. 2). Day weighting would have shifted values by only
  +0.03 to +0.13 °F. Closes finding 1.
- **Annual avg temperature aggregation (2026-09-15):** area-weighted county
  means (sub-cell coverage fraction × cos(latitude)), matching Köppen. Closes
  finding 2 for this metric.
- **Annual avg temperature completeness (2026-09-15):** a county is blank
  unless all 12 monthly values are present (WMO-No. 1203 §4.3.3).
- **Annual avg temperature in Alaska and Hawaii (2026-09-15):** left blank for
  now; tracked as the cross-filter "Alaska and Hawaii coverage" open decision.