Temperature inversion Possible
Daily PM2.5 peaked at 47.6 µg/m³ near Springfield across 1 covered metro home to 464,151 people.
Why we think this happened
Springfield's three-monitor PM2.5 increase coincided with sharp carbon-monoxide, nitrogen-dioxide, and sulfur-dioxide increases. An exact-date NWS discussion reported a low-level inversion keeping interior winds calm. Together they support inversion trapping at possible confidence while leaving the accumulated emissions mixture unidentified.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
U.S. EPA AirData hypothesis
EPA records show a median daily PM2.5 value of 40.1 micrograms per cubic meter across 3 monitors during the event, compared with 14.85 before and 6.5 after. Same-window context included Carbon monoxide 1.2331 Parts per million, Nitrogen dioxide (NO2) 37.5 Parts per billion, Sulfur dioxide 19.2202 Parts per billion, Ozone 0.0098 Parts per million.
National Weather Service via Iowa Environmental Mesonet · Jan 19, 2003 hypothesis
NWS Taunton reported on the event morning that a low-level inversion was keeping winds calm across interior southern New England.
Inference, not direct attribution
Documented inversion overlap: The event overlaps a documented inversion period, but the retained material does not directly attribute the measured PM2.5 episode.
Evidence path
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.
Source or mechanism
Documented inversion overlap. The event overlaps a documented inversion period, but the retained material does not directly attribute the measured PM2.5 episode.
Air-mass movement
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.
Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 2.2 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓Event autopsy
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.
Springfield, MA
Monitor comparison window 2003-01-16 to 2003-01-22 · PM2.5 target: LIBERTY ST PARKING LOT
170% above nearby days
1 calm hour observed
0 hours at or below 3 miles
170% higher than surrounding days
94% higher than surrounding days
82% higher than surrounding days
179% higher than surrounding days
68% lower than surrounding days
5 kt maximum · 1 of 17 observed hours calm
0 observed hours at or below 3 miles
-7.6°F to 17.6°F
92% maximum
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.
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
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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Springfield, MA | 47.6 µg/m³ | 2.2 | Jan 19, 2003 | #17 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
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.
National Weather Service via Iowa Environmental Mesonet
NWS Taunton reported on the event morning that a low-level inversion was keeping winds calm across interior southern New England.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The discussion identifies a trapping mechanism but does not identify the emissions accumulated below it.
U.S. EPA AirData
EPA records show a median daily PM2.5 value of 40.1 micrograms per cubic meter across 3 monitors during the event, compared with 14.85 before and 6.5 after. Same-window context included Carbon monoxide 1.2331 Parts per million, Nitrogen dioxide (NO2) 37.5 Parts per billion, Sulfur dioxide 19.2202 Parts per billion, Ozone 0.0098 Parts per million.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The measured fingerprint establishes the episode and co-pollutant pattern but cannot uniquely apportion its sources.
U.S. EPA EQUATES CMAQ via Remote Sensing Information Gateway
EPA's retrospective 12-kilometer model reproduced an event-centered fine-mass increase of 2.0825 times adjacent modeled days. The modeled mixture was 36.3% organic matter, 46.4% secondary ions, 4.2% soil, and 7.4% elemental carbon.
Context for the event; this item does not establish the attributed cause by itself.
EQUATES is a retrospective chemical-transport model, not a monitor observation or source-apportionment determination; it is retained as compatible composition context only.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
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.