{
  "version": "1.0.0",
  "fields": {
    "timestamp_utc": "Hourly timestamp in UTC, ISO 8601; one row per expected hour.",
    "observed_ft": "NOAA verified hourly_height value, feet relative to station MLLW; null/blank if missing or invalid.",
    "predicted_ft": "NOAA hourly tide prediction at the exact timestamp, feet relative to station MLLW; null/blank if missing or invalid.",
    "difference_ft": "Observed minus predicted, feet, for included pairs only; positive means observed higher. Null/blank for excluded pairs.",
    "observation_flags": "Original NOAA hourly-height flags I,L: inferred value and expected-limit flag. Only 0,0 admitted. A quoted CSV field preserves the comma.",
    "included": "Boolean: valid numeric observation and prediction, with flags 0,0.",
    "exclusion_reasons": "Array in JSON, semicolon-separated in CSV; empty for admitted pairs. Missing observation/prediction, invalid numeric value or flagged observation."
  },
  "notes": [
    "No blank converted to zero; no interpolated hours.",
    "English water-height units are feet. GMT request timestamps are represented as UTC.",
    "Source hourly product is verified; flags are not a measurement-uncertainty estimate.",
    "Period means are hour-weighted and independently rounded; one year is not a seasonal climatology."
  ],
  "periodSummaryFields": {
    "period": "UTC calendar month or meteorological month group; winter combines January, February and December 2025.",
    "expected_hours": "Number of hourly grid positions in this period.",
    "paired_hours": "Eligible exact-time pairs after quality screening.",
    "excluded_hours": "Expected hours not admitted.",
    "coverage_percent": "100 times paired/expected hours.",
    "mean_observed_ft": "Mean observed height over admitted hours, feet MLLW.",
    "mean_predicted_ft": "Mean prediction over the same admitted hours, feet MLLW.",
    "mean_difference_ft": "Arithmetic mean of observed minus predicted, ft.",
    "mean_absolute_difference_ft": "Arithmetic mean of absolute differences, ft."
  }
}