Detection and trends of atmospheric long-lived halogenated gases from space with IASI
Notice bibliographique
Résumé
Since the 1900s, emissions of CFCs and other long-lived halogenated species have profoundly affected the chemical and radiative equilibrium of our atmosphere. These halogenated compounds are known to be powerful greenhouse gases and contribute, for chlorinated and brominated compounds, to the depletion of the ozone layer and to the development of the ozone hole. With the aim of mitigating their deleterious impact on the environment, most long-lived halogenated species are controlled by international treaties, the most famous of which is the Montreal Protocol of 1987. Their monitoring is essential to evaluate the effectiveness of international regulations with regard to emissions, and ultimately to assess the environmental impacts of the changes at play. Sustained global networks located on ground have provided highly accurate measurements of the atmospheric concentrations of long-lived halogenated species for 50 years. The aim of this thesis is to assess the potential of infrared satellite sounders operating in the nadir geometry, to contribute to their monitoring and thereby complement existing surface measurement networks. The research work is centered on the exploitation of the measurements from the IASI sounder. Its stability and the consistency between the diff erent instruments on the successive Metop (A,B and C) is remarkable and makes it a reference for climate monitoring. Among other things, IASI offers the potential to investigate trends in the concentration of various species better than with any other previous or current hyperspectral infrared sounder. The low noise of IASI radiances is also such that even weakly absorbing atmospheric constituents can be tracked, on single or at least on averaged spectra. As a first step, we sought to determine which long-lived halogenated species can be detected in IASI spectra. To achieve this, we have developed an innovative methodology, based on spectral whitening, which allows to isolate the weak spectral signatures of several long-lived halogenated species by removing most of the largest and most variable spectral features from IASI spectra. The major outcome is the unambiguous identifi cation of eight long-lived halogenated species, namely CFC-11, CFC-12, CCl4 ,HCFC-22, HCFC-142b, HFC-134a, CF4 and SF6. Three of these (HCFC-142b, HFC-134a, SF6 ) were never detected before. In a second stage, we sought to retrieve the atmospheric concentrations of the species detected in the first part of the work. For that, we rely on an unconstrained generalized least squares estimation retrieval methodology. Focussing on two oceanic regions over northern and southern mid-latitudes, we derive the monthly concentrations between 2008 and 2022. The trend evolution in the diff erent chemical species, either negative or positive, is validated against what is observed with ground-based measurement networks and other satellite data. The results demonstrate the potential of IASI and follow-up missions for establishing a unique long-term time series of themost important long-lived halogenated species.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».