Seasonal variations of PAN, PPN, and O<sub>3</sub> at the upper Midwest PROPHET site
Bibliographic record
Abstract
Continuous measurements of peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and ozone (O3) were made from June 1997 through August 1999 at a ground site in the upper Midwest as part of the Program for Research on Oxidants: Photochemistry, Emissions, and Transport (PROPHET). Relatively clean air originating in Canada is transported to the site from the northwest, while more polluted air originating in the metropolitan regions of the Midwest is transported mainly from the southwest and the southeast. Monthly averages of PAN are a minimum in summer /early winter (July‐January) with mixing ratios ranging from 125 to 259 parts per trillion by volume (pptv), while maximum monthly average PAN levels are observed in February through June with mixing ratios of 325–390 pptv. Monthly average ozone mixing ratios ranged from 42 to 46 ppbv in the spring/summer months and 23–32 ppbv in the autumn/early winter months. Correlation among species were examined on a monthly basis. There is a dramatic variation in the PPN/PAN slope from summer to winter with the general trend a maximum slope in the winter ranging from 0.20 to 0.23 and a minimum slope during the summer months ranging from 0.09 to 0.13. The degree of association, r2, is strong in all months, ranging from 0.76 to 0.96. A photochemical box model was used to determine if the seasonal variation could be attributed solely to the summertime production of PAN from isoprene. Box model results indicate that the seasonal variation in the PPN/PAN slope when produced from anthropogenic precursors can be explained by seasonal changes in temperature and photolysis rates, and the production of PAN from isoprene in the summer only serves to increase the seasonal difference in slope.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".