Validation of satellite OClO products from S5P/TROPOMI and MetopA and B/GOME2 
Bibliographic record
Abstract
Chlorine dioxide is an indicator for chlorine activation in the stratosphere, of importance for understanding spring-time ozone depletion processes in the polar regions of both hemispheres. Within the EUMETSAT AC SAF working group, chlorine dioxide (OClO) was retrieved from the GOME-2 instruments on MetOp-A and MetOp-B platforms, respectively over the time periods 2007-2016 and 2012-2016. Moreover, recent work performed as part of the S5p+ Innovation programme has led to the creation of an additional dataset derived from the TROPOMI instrument, extending the OClO time series in 2018-2020. This study analyses the quality of both OClO slant column (SCD) datasets by comparing them to ground-based DOAS zenith-sky measurements at a selection of 8 stations in Arctic and Antarctic regions: Eureka (80°N), Ny Alesund (79°N), Kiruna (68°N), Harestua (60°N), Marambio (64°S), Belgrano (78°S), Neumayer (71°S) and Arrival Heights (78°S). To allow for comparison with satellite data, ground-based OClO spectral analyses are performed using yearly fixed reference spectra recorded at low SZA in the absence of chlorine activation. Furthermore, an additional bias-correction is applied in post-processing to generate a consistent long-term OClO data record covering the 2007-2020 period. Daily comparisons of satellite and ground-based SCD data pairs corresponding to similar SZA conditions are performed, assuming similar stratospheric light paths in satellite nadir and ground-based zenith-sky geometries. Daily mean OClO SCD time-series show that satellite and ground-based observations agree well at all stations in terms of short-term variability and seasonal variation. Linear regression plots show a correlation coefficient R of about 0.97, a slope of 0.9 and an intercept of less than 1x1013 molec/cm² for TROPOMI, while for GOME-2 results are more noisy and tend to be biased low, with correlation coefficients between 0.76 and 0.88, slopes between 0.65 and 0.74 and intercepts up to 2.4 x1013 molec/cm².
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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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".