Mixed causes Possible
Daily PM2.5 peaked at 38.2 µg/m³ near Jackson across 1 covered metro home to 606,178 people.
Why we think this happened
Jackson's PM2.5 episode coincided with an exact-date strong low-level inversion and an NWS report that smoke from minor area burns was reducing visibility at Jackson's airport. A later discussion said remnant smoke particles would hasten fog. The evidence supports a mixed local-burn-smoke and inversion episode at possible confidence, but it does not identify the burn type or apportion the daily PM2.5 value.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
National Weather Service via Iowa Environmental Mesonet · Feb 19, 2011 hypothesis
During the local evening of February 19, NWS Jackson reported smoke from minor area burns affecting visibility at KJAN; a later update said remnant smoke particles would hasten fog formation.
National Weather Service via Iowa Environmental Mesonet · Feb 19, 2011 hypothesis
NWS Jackson reported that its event-morning sounding showed a strong low-level inversion, with generally light winds under high pressure.
U.S. EPA AirData hypothesis
EPA records show a median daily PM2.5 value of null micrograms per cubic meter across 2 monitors during the event, compared with 11.9 before and 17.1 after. Same-window context included PM10 Total 0-10um STP null Micrograms/cubic meter (25 C), Carbon monoxide 0.2791 Parts per million, Sulfur dioxide 0.7913 Parts per billion, Ozone 0.0276 Parts per million.
Inference, not direct attribution
official_local_burn_smoke_plus_inversion_possible.v1: This inference is recorded in the catalog methodology.
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
official_local_burn_smoke_plus_inversion_possible.v1. This inference is recorded in the catalog methodology.
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 1.7 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 “Mixed causes” explanation; it does not assign the cause by itself.
Jackson, MS
Monitor comparison window 2011-02-16 to 2011-02-22 · PM2.5 target: University Medical Center
98% above nearby days
1 calm hour observed
Haze reported during 9 hours
98% higher than surrounding days
41% higher than surrounding days
37% higher than surrounding days
15% lower than surrounding days
7 kt maximum · 1 of 11 observed hours calm
2 observed hours at or below 3 miles
57°F to 79°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.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Jackson, MS | 38.2 µg/m³ | 1.7 | Feb 19, 2011 | #11 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 Jackson reported that its event-morning sounding showed a strong low-level inversion, with generally light winds under high pressure.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The inversion establishes a trapping mechanism but does not identify the emissions below it.
National Weather Service via Iowa Environmental Mesonet
During the local evening of February 19, NWS Jackson reported smoke from minor area burns affecting visibility at KJAN; a later update said remnant smoke particles would hasten fog formation.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The source does not identify whether the area burns were prescribed, agricultural, debris, or another controlled or uncontrolled burn type.
U.S. EPA EQUATES CMAQ via Remote Sensing Information Gateway
EPA's retrospective 12-kilometer model reproduced an event-centered fine-mass increase of 1.6871 times adjacent modeled days. The modeled mixture was 47.4% organic matter, 21.1% secondary ions, 15.8% soil, and 5.3% 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.
U.S. EPA AirData
EPA records show a median daily PM2.5 value of null micrograms per cubic meter across 2 monitors during the event, compared with 11.9 before and 17.1 after. Same-window context included PM10 Total 0-10um STP null Micrograms/cubic meter (25 C), Carbon monoxide 0.2791 Parts per million, Sulfur dioxide 0.7913 Parts per billion, Ozone 0.0276 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.
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.