Two-dimensional observations of dichloromethane-rich air masses transported from the Asian summer monsoon region across the North Pacific
Bibliographic record
Abstract
Dichloromethane (CH2Cl2) is known to be emitted by industrial processes and suspected to be capable of delaying the recovery of the stratospheric ozone layer significantly. A rapid rise of its global emissions over the last decades, with the majority being located in East and South East Asia, is documented in the literature. We present unique observations of CH2Cl2-rich air masses over the North Pacific, Canada and Alaska by the infrared limb imager GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere). During the boreal summer of 2023, GLORIA was deployed aboard the German research aircraft HALO (High Altitude and LOng Range Research Aircraft) in the framework of the PHILEAS campaign (Probing High Latitude Export of Air from the Asian Summer Monsoon). Two-dimensional vertical cross-sections of CH2Cl2 derived from GLORIA observations in August and September 2023 show large plumes with high mixing ratios of typically up to ~300 pptv far away from their anticipated source regions. Up to 450 pptv are observed locally, which corresponds to ~700% of the northern hemispheric background in that season. Air masses with high CH2Cl2 mixing ratios are detected in the free troposphere and moderately enhanced mixing ratios are observed partly also in the tropopause region. Using backward trajectories and simulations by the Chemical Lagrangian Model of the Stratosphere (CLaMS), the transport pathways and timescales of the observed air masses are analysed. Our analysis suggests that East Asia is a major source region of the observed air masses. Together with the model data and in situ observations by HAGAR-V (High Altitude Gas AnalyzeR-V) and GhOST (Gas chromatograph for Observational Studies using Tracers), the GLORIA observations provide new insights into the long-range transport of CH2Cl2-rich airmasses from the Asian Summer Monsoon region. GLORIA is an airborne demonstrator for the ESA Earth Explorer 11 candidate CAIRT (Changing-Atmosphere Infra-Red Tomography explorer), which is currently in the final selection round and would provide new opportunities to study a multitude of ozone- and climate-relevant trace species continuously.
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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 | 0.001 |
| Science and technology studies | 0.000 | 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) | 0.000 | 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".