Observations of reactive nitrogen oxide fluxes by eddy covariance above two midlatitude North American mixed hardwood forests
Bibliographic record
Abstract
Abstract. Significant knowledge gaps persist in the understanding of forest–atmosphere exchange of reactive nitrogen oxides, partly due to a lack of direct observations. Chemical transport models require representations of dry deposition over a variety of land surface types, and the role of canopy exchange of NOx (= NO + NO2) is highly uncertain. Biosphere–atmosphere exchange of NOx and NOy (= NOx + HNO3 + PANs + RONO2 + pNO3− + ...) was measured by eddy covariance above a mixed hardwood forest in central Ontario (Haliburton Forest and Wildlife Reserve, or HFWR), and a mixed hardwood forest in northern lower Michigan (Program for Research on Oxidants: Photochemistry, Emissions and Transport, or PROPHET) during the summers of 2011 and 2012 respectively. NOx and NOy mixing ratios were measured by a custom-built two-channel analyser based on chemiluminescence, with selective NO2 conversion via LED photolysis and NOy conversion via a hot molybdenum converter. Consideration of interferences from water vapour and O3, and random uncertainty of the calculated fluxes are discussed. NOy flux observations were predominantly of deposition at both locations. In general, the magnitude of deposition scaled with NOy mixing ratios. Average midday (12:00–16:00) deposition velocities at HFWR and PROPHET were 0.20 ± 0.25 and 0.67 ± 1.24 cm s−1 respectively. Average nighttime (00:00–04:00) deposition velocities were 0.09 ± 0.25 cm s−1 and 0.08 ± 0.16 cm s−1 respectively. At HFWR, a period of highly polluted conditions (NOy concentrations up to 18 ppb) showed distinctly different flux characteristics than the rest of the campaign. Integrated daily average NOy flux was −0.14 mg (N) m−2 day−1 and −0.34 mg (N) m−2 day−1 (net deposition) at HFWR and PROPHET respectively. Concurrent wet deposition measurements were used to estimate the contributions of dry deposition to total reactive nitrogen oxide inputs, found to be 22 and 40% at HFWR and PROPHET respectively.
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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 | 0.001 | 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".