Temperature inversion Possible
Daily PM2.5 peaked at 25.6 µg/m³ near North Port across 1 covered metro home to 934,956 people.
Why we think this happened
A two-monitor Sarasota PM2.5 increase coincided with higher nitrogen dioxide, sulfur dioxide, and carbon monoxide; weak surface wind; observed haze; and an exact-date NWS report of a strong subsidence inversion over the Sarasota corridor. The evidence supports a temperature-inversion trapping mechanism at possible confidence. It does not establish which anthropogenic sources supplied the particle mixture.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
National Weather Service Tampa Bay Area Forecast Discussion via Iowa Environmental Mesonet · Jan 17, 2002 hypothesis
The exact-date NWS discussion described very moist air below roughly 880 millibars, a strong subsidence inversion with very dry air above, and a cloud band extending from St. Augustine through Lakeland to Sarasota.
U.S. EPA AirData hypothesis
EPA records show median daily PM2.5 of 23.55 micrograms per cubic meter across two monitors, about 3.5 times the adjacent-window comparison. Nitrogen dioxide was about 2.3 times its adjacent comparison, sulfur dioxide about 1.6 times, and carbon monoxide about 1.1 to 1.2 times; ozone did not rise.
National Weather Service surface observations via Iowa Environmental Mesonet · Jan 17, 2002 hypothesis
Sarasota-Bradenton recorded a median wind speed of three knots, 13 of 24 hours at or below three knots, seven calm hours, six haze hours, and visibility as low as three miles.
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 1.2 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.
North Port-Sarasota-Bradenton, FL
Monitor comparison window 2002-01-14 to 2002-01-20 · PM2.5 target: Bee Ridge Park
254% above nearby days
7 calm hours observed
Haze reported during 6 hours
254% higher than surrounding days
13% higher than surrounding days
133% higher than surrounding days
57% higher than surrounding days
About the same as surrounding days
6 kt maximum · 7 of 24 observed hours calm
6 observed hours at or below 3 miles
55°F to 67°F
93% 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 |
|---|---|---|---|---|
| North Port-Sarasota-Bradenton, FL | 25.6 µg/m³ | 1.2 | Jan 17, 2002 | #18 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 Tampa Bay Area Forecast Discussion via Iowa Environmental Mesonet
The exact-date NWS discussion described very moist air below roughly 880 millibars, a strong subsidence inversion with very dry air above, and a cloud band extending from St. Augustine through Lakeland to Sarasota.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The forecast discussion documents a vertical cap over the area but does not identify the sources or chemical composition of the accumulated particles.
National Weather Service surface observations via Iowa Environmental Mesonet
Sarasota-Bradenton recorded a median wind speed of three knots, 13 of 24 hours at or below three knots, seven calm hours, six haze hours, and visibility as low as three miles.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
One airport station cannot describe every neighborhood in the metro or establish the vertical temperature profile by itself.
U.S. EPA AirData
EPA records show median daily PM2.5 of 23.55 micrograms per cubic meter across two monitors, about 3.5 times the adjacent-window comparison. Nitrogen dioxide was about 2.3 times its adjacent comparison, sulfur dioxide about 1.6 times, and carbon monoxide about 1.1 to 1.2 times; ozone did not rise.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The multi-pollutant response supports accumulated combustion and industrial pollution but does not apportion individual source sectors or particle composition.
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.