Untersuchung organischer Spurengase in der Troposphäre : globale Verteilungen, jahreszeitliche Variationen und langfristige Trends
Bibliographic record
Abstract
In this study the spatial and temporal variations of the mixing ratios of organic trace gases in the lower troposphere were investigated . Air samples were collected in stainless steel canisters and analyzed for their contents of carbon dioxide, carbon monoxide, methane, nonmethane hydrocarbons and halocarbons. Characterizations of the used gas chromatographic systems and the resuits of international intercomparison experiments showed that the analytical methods are suitable for the measurement of organic trace gases at Iow concentration levels. The latitudinal distribution of trace gases in the boundary layer over the Atlantic was measured during the cruise of the German research vessel `Polarstern' as part of the ALBATROSS campaign (October/November 1996) . The measurements covered a latitude range between 67°N and 45°S . In this work the distribution of some halogenated hydrocarbons in marine air was measured for the First time . Highest mixing ratios of hydrocarbons and several anthropogenic halocarbons (CH2C1-,, CHCL, 1,2-C 2H4C12 , C7HC13, C2CL und CH3Br) were observed in the Northern Hemisphere between 42°N to 67°N latitude. The mixing ratios of 1,1-dichloroethene, 1,1,1-trichloroethane, dibromomethane, tribromomethane and iodomethane showed a rather uniform distribution in both hemispheres . The observed mixing ratios of methylchloride and tetrachloromethane showed Iow maxima near the equator. The seasonal variations of the mixing ratios of organic trace gases were measured in whole air samples collected in Alert (Canadian Arctic) over a time period of 7 years between January 1989 and July 1996 . The resuits allowed to estimate lang term trends of mixing ratios for a number of compounds . The mixing ratios of most hydrocarbons decreased between 2.2 to 14 .4 % per year. Except tetrachloroethene, for other halocarbons (CH3CI, CH-C12 and C,HCL), no significant trends of the Fnixing ratios were found. Tetrachloroethene showed an annual decrease of 8 .3 % per year. The observed mixing ratios of the trace gases showed pronounced seasonal variations with maxima in winter and minima in sumrner. These variations are mainly caused by the meteorologieal conditions in the Arctic. The ratios of winter and summer concentrations were different for each compound. The plot of the winter/summer ratio as a function of the reaction rates with OH radicals showed a maximum for C4-C5 -alkanes. A global Chemical Tracer Model (CTM) allowed a qualitative simulation of the observed seasonal variations. For the quantitative description of the observed data with the CTM local sources of hydrocarbons are necessary. The estimated source strength ranged from less then 0 .09 up to 0 .9 ng .m 2 . s -' depending an the hydrocarbon . Due to the location of Alert the ocean is discussed as a local source for these hydrocarbons
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| 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".