Winter inversion
January 19-22, 2009 Wasatch Front winter-inversion episode
Daily PM2.5 peaked at 80.4 µg/m³ near Provo across 3 covered metros home to 2.7 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 6.6 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 18 million cigarettes. An awareness illustration of outdoor exposure at 22 µg/m³ per cigarette (Berkeley Earth), counting only the event's ranked days; not a medical dose.
Episode peak
-- cigarettes
The smoke map's scale, replayed over this event: the surface interpolates between covered metros' daily records, framed to the affected region. Hover for a reading, click a metro to pin it to the card. Days a monitor did not report draw nothing.
What happened, in the record
Both supplied scientific corroboration records support a contemporaneous January 2009 Wasatch Front winter-inversion episode, and their affected intervals overlap across January 21-22. Both supplied scientific corroboration records support a contemporaneous January 2009 Wasatch Front winter-inversion episode, and their affected intervals overlap across January 21-22.
Sequence: Provo (Jan 20) → Salt Lake City (Jan 21) → Ogden (Jan 22)
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Provo-Orem, UT | 80.4 µg/m³ | 10.6 | Jan 21, 2009 | #12 of its top days |
| Salt Lake City, UT | 74.3 µg/m³ | 6.7 | Jan 21, 2009 | #16 of its top days |
| Ogden-Clearfield, UT | 56.4 µg/m³ | 5.1 | Jan 22, 2009 | #24 of its top days |
"Cigarettes, whole event" totals a metro's ranked event days at 22 µg/m³ per cigarette: what a person outdoors there breathed across the event, as the illustration. "All-time standing" is where this episode's days sit in each metro's ranked record (worst-area measure, since 1999). Full local context is on each metro's Air Records page.
The evidence
Agency and publisher pages 1
- Design and Characterization of a Human Exposure Chamber and Inversion Episodes in Salt Lake City, Utah in January/February of 2009 A 2009 thesis documents PM2.5 chemical analysis during inversion periods in Salt Lake City in January–February 2009, corroborating a contemporaneous Wasatch Front winter-inversion episode; it does not resolve the precise dates or directly assess Ogden and Provo.
What remains uncertain
- The retained scientific record corroborates a contemporaneous Wasatch Front inversion period but does not resolve the episode's precise boundaries.
Status and provenance
Research preview: this record carries research-only status and its boundaries, cause, and name may change as evidence review completes. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula.