Dispersion from an area source in the unstable surface layer: an approximate analytical solution
Bibliographic record
Abstract
An approximate solution to the advection‐diffusion equation is given, applying to a plume in the unstably stratified surface layer emanating from a finite ground‐level area source of trace gas. The approximation consists firstly of representing the mean wind profile by a power law, and secondly, in ‘splitting’ the governing equation so as to determine two components of the mean concentration that, in sum, satisfy the boundary conditions. The solution, which is easy to evaluate, is compared with numerical simulations using a standard Lagrangian stochastic trajectory model (LSM) and, provided the ratio of the upwind fetch of source to the Obukhov length is not too large ( ), agreement is very good. The Lagrangian model, in turn, is shown to be consistent with the Project Prairie Grass (PPG) dispersion data, subject only to the tuning of a flexible constant whose optimal value carries the implication that the ratio (Sc) of the eddy viscosity to the (far field) eddy diffusivity is not unity in the neutral limit, but rather Sc≈0.64. It seems unlikely this calibration results from having neglected deposition of the PPG ‘tracer’ (sulphur dioxide) to the surface.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".