Deseret News · Feb 5, 2002 corroborates
How many days of haze?
Contemporaneous reporting described February 5 as the seventh day of a Wasatch Front inversion, placing February 4 inside the documented pollution-trapping episode.
Temperature inversion Likely
2002-02-04 Ogden-Clearfield, UT temperature-inversion pollution episode
Daily PM2.5 peaked at 59.8 µg/m³ near Ogden across 1 covered metro home to 667,681 people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.4 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 1.6 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.
Why we think this happened
The basis for “Temperature inversion”
Exact-period reporting identifies a multiday Wasatch Front inversion trapping pollution.
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
Evidence path
From source to city
A cause is more convincing when the record connects three things: something happened, the air mass moved toward the region, and local instruments responded. Here is how much of that chain is documented for this event.
- 1Documented
Source or mechanism
Temperature inversion
Contemporaneous reporting described February 5 as the seventh day of a Wasatch Front inversion, placing February 4 inside the documented pollution-trapping episode.
View supporting source ↗ - 2Research gap
Air-mass movement
The transport path has not been reconstructed
The retained record does not yet show how air traveled from the proposed source to these metros. A trajectory replay or dated plume analysis belongs here.
- 3Documented
Local response
59.8 µg/m³ near Ogden
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 2.7 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓
Event autopsy
What the instruments saw
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Temperature inversion” explanation; it does not assign the cause by itself.
Ogden-Clearfield, UT
Monitor comparison window 2002-02-01 to 2002-02-07 · PM2.5 target: Ogden
0% above nearby days
About the same as surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 56.5 µg/m³
About the same as surrounding days
Before28.2 µg/m³ Event56.5 µg/m³ After83.4 µg/m³
PM10 79 µg/m³
About the same as surrounding days
Before47 µg/m³ Event79 µg/m³ After106 µg/m³
Carbon monoxide 1.17 ppm
About the same as surrounding days
Before1 ppm Event1.17 ppm After1.24 ppm
Nitrogen dioxide 56.6 ppb
About the same as surrounding days
Before48.2 ppb Event56.6 ppb After68.9 ppb
Sulfur dioxide 4.65 ppb
15% lower than surrounding days
Before3.38 ppb Event4.65 ppb After9.33 ppb
Atmospheric conditions
Nearby EPA weather observationsAbout the same as surrounding days
Source: U.S. EPA AirData daily observations and, where available, nearby ASOS/AWOS surface observations. Values are descriptive medians over the retained monitor set; missing measurements remain missing. Transport and source evidence remain separate layers because this instrument pattern does not assign a cause by itself.
Measured daily PM2.5 at EPA monitors, as cigarette-equivalents
EPA monitors sit in metro areas, so the colour clusters there. Land between and beyond
them is unmeasured, not clean: this map shows where IAQng has readings, not the extent
of the smoke.
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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.
Views from the selected metro
Camera views near
Select a metro on the map to see nearby cameras. Where an operator archive reaches the event, drag the divider to compare two moments, adjust either date and time, or play the available event-day frames. Camera imagery is visual context, not an air-quality measurement or proof of smoke.
No useful public camera views are currently available within 80 km of this metro.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Ogden-Clearfield, UT | 59.8 µg/m³ | 2.7 | Feb 4, 2002 | #19 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.
Public evidence library
What supports this account
Each card states what a source supports—and what it does not. Official records, research, reporting, community observations, and transparent inferences remain visibly different kinds of evidence.
How many days of haze?
Deseret News
Contemporaneous reporting described February 5 as the seventh day of a Wasatch Front inversion, placing February 4 inside the documented pollution-trapping episode.
What it supports
A retained source supports the attributed cause for the stated place and dates.
Limit
The article covers the Wasatch Front collectively rather than reporting an Ogden-only source apportionment.
What remains uncertain
- The inversion mechanism is supported; individual emissions within the trapped mixture are not apportioned.
Status and provenance
Likely Applicable reporting or a supported inference makes this the best current causal explanation.
This episode was grouped from the monitor record by the catalog pipeline and given its cause from the evidence listed above. It has not been individually reviewed and signed off, so its boundaries, cause, and name may change as evidence accumulates. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula. If it is wrong, tell us.