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Aviation NOx emissions have not only an impact on global climate by changing ozone and methane levels but also contribute to deteriorate local air quality. In order to properly assess the co-benefit with air quality improvement and the trade-off with the climate change associated with CO2, it appears essential to better quantify the climate impact of aircraft NOx emissions. A new version of the LMDZ-INCA global model, including both tropospheric and stratospheric chemistry and the sulfate-nitrate-ammonium cycle, is applied to re-evaluate the impact of aircraft NOx and aerosol emissions on climate. The results confirm that the efficiency of NOx to produce ozone is very much dependent on the injection height. For the baseline simulation and reference scenario this efficiency is 6.6 TgO3/TgN. The efficiency increases with the background methane and NOx concentrations and with decreasing aircraft NOx emissions. The same findings translate to the associated ozone radiative forcing which exhibits a fairly constant value per ozone mass change of 3.4 mW/m2/TgO3. The methane lifetime variation is less sensitive to the aircraft NOx emission location than the ozone change. The change in CH4 mixing ratio itself represents 75 % of the total methane forcing. The indirect changes through long-term tropospheric ozone, stratospheric water vapour and methane oxidation to CO2 contribute for 19 %, 4 % and 1 %, respectively. The net NOx radiative forcing (O3 + CH4) is largely affected by the revised CH4 radiative forcing formula which increases the total CH4 negative forcing by 15 %. As a consequence, the ozone positive forcing and the methane negative forcing largely offset each other resulting in a slightly positive forcing for the present-day. However, in the future, the net forcing turns to negative due essentially to higher methane background concentrations. Additional radiative forcings involving particle formation arise from aircraft NOx emissions since the increased OH concentrations are responsible for an enhanced conversion of SO2 to sulfate particles. Aircraft NOx emissions also increase the formation of nitrate particles in the lower troposphere. However, in the upper-troposphere, increased sulfate concentrations favor the titration of ammonia leading to lower ammonium nitrate concentrations. The total forcing from sulfate and nitrate aerosols associated with NOx emissions is negative and is estimated to -3.0 mW/m2/TgN for the present-day. When these aerosol radiative forcings are considered, the total NOx forcing turns from a positive value to a negative value even for present-day conditions. Hence, total radiative forcing from aircraft emissions associated with changes in atmospheric chemistry and direct aerosols forcings is negative for both present-day and future (2050) conditions. NOx emissions only cause a negative forcing representing about 45 % of the total forcing. The negative forcing associated with sulfates largely dominates the effect of the other particles. The sulfate direct radiative forcing is estimated to be associated for about 50 % with the direct SO2 and SO4 aircraft emissions and for about 50 % with the increased conversion of SO2 to SO4 at higher OH concentrations, and hence related to the NOx emissions. The net effect of decreasing (resp. increasing) the flight altitude by 2000 ft (about 610 m) is to increase (resp. decrease) the total negative forcing by 57 % (resp. 65 %). The variation of the total forcing with flight altitude is dominated by the high sensitivity of the ozone positive forcing to the altitude of the perturbation. Several mitigation options involving flight aircraft operation and cruise altitude changes, traffic growth, engine technology, and fuel type, exist to reduce the climate impact of aircraft NOx emissions. However, the climate forcing of aircraft NOx emissions is likely to be small or even switch to negative (cooling) depending on atmospheric NOx or CH4 future background concentrations or when the NOx impact on sulfate and nitrate particles is considered. There remain large uncertainties on the NOx net impact on climate effect calculation. Nevertheless, the results suggest that reducing aircraft NOx emissions is primarily beneficial for improving air quality. For climate consideration, one option to reduce uncertainties in mitigation strategies might be to prioritize the reduction of CO2 aircraft emissions which have a well-established and long-term impact on climate, however this reduces the overall mitigation potential.

The 21th WMO/IAEA Meeting on Carbon Dioxide, Other Greenhouse Gases and Related Measurement Techniques (GGMT-2022) was organized in Wageningen, The Netherlands from 19-21 September and was back to back with the ICOS Science Conference 2022 (13-15 September 2022) and a Transcom community meeting (16+17 September 2022). The themes for this GGMT meeting were: 1. Quality assurance of greenhouse gas measurements (including reference standards, comparison activities and good practices) 2. Quality assurance of the measurements of the stable isotopes (including reference standards, comparison activities and good practices) 3. Measurements and quality assurance for 14C, O2/N2 and related tracers 4. Data products and utilization of the observations 5. Advances in the traditional greenhouse gas measurement techniques 6. Emerging Observation Techniques including low-cost sensors, Remote Sensing and Integration of Observations 7. Observations from the mobile platforms (aircraft, drone, balloon, etc) and over/in the ocean 8. Urban Observations and Networks The meeting received 93 contributions for which the abstracts are contained in this document. The presentations and posters are available online at https://www.ggmt2022.online/ggmt-2022/posters-and-presentations-ggmt/

The ADRIMED campaign provides measurements of all key parameters regarding atmospheric composition in the Mediterranean area during the summer 2013. This is an opportunity to quantify the ability of current models to adequately represent the atmospheric composition in this complex region, which is influenced by anthropogenic emissions from Europe, Africa, the Middle-East and from shipping activities as well as mineral dust emissions mostly from the arid areas in Africa, sea-salt emissions, biomass burning emissions and biogenic emissions from the vegetation. The CHIMERE model in its present version is a chemistry-transport model which takes into account all these processes. We show here by simulating the period from 5 June to 15 July 2013 with the CHIMERE model and comparing the results to both routine and specific ADRIMED measurements that this model allows an adequate representation the atmospheric composition over the western Mediterranean, in terms of ozone concentration, particulate matter (PM) and aerosol optical depth (AOD). It is also shown that the concentrations of PM on all the considered area is dominated by mineral dust, even though local dust emissions in Europe are certainly overestimated by the model. A comparison with sulphate concentrations at Cape Corsica exhibits some discrepancies related to the regridding of shipping emissions.

Cette thèse présente une étude empirique et théorique approfondie de l'évolution spectrale des étoiles naines blanches, avec un accent particulier sur les naines blanches chaudes. La composition atmosphérique (et donc l'apparence spectrale) de ces cadavres stellaires peut changer drastiquement avec le temps à mesure qu'ils se refroidissent. Ce phénomène est généralement interprété comme le résultat d'une compétition entre divers mécanismes de transport des éléments dans l'enveloppe stellaire (tels que la diffusion, la convection, les vents et l'accrétion), mais demeure mal compris à plusieurs égards. Il est impératif de remédier à cette situation pour être en mesure d'exploiter le potentiel immense des naines blanches pour notre compréhension du passé de la Galaxie. Pour mieux caractériser l'incidence de l'évolution spectrale, nous effectuons tout d'abord une analyse spectroscopique exhaustive de près de 2000 naines blanches chaudes (Teff > 30,000 K) observées par le relevé SDSS. Nous déterminons les propriétés atmosphériques (notamment la température effective et la composition de surface) de ces objets à l'aide d'un nouvel ensemble de modèles d'atmosphère calculé spécifiquement à cet effet. En examinant la fréquence relative des étoiles riches en hydrogène et riches en hélium en fonction de la température, nous obtenons pour la première fois un portrait empirique détaillé de l'évolution spectrale des naines blanches chaudes. Plus spécifiquement, nous déduisons (1) qu'environ une étoile sur quatre arrive sur la séquence de refroidissement avec une atmosphère d'hélium, et (2) qu'environ deux tiers de ces objets développent ultérieurement une atmosphère d'hydrogène. En outre, nous accordons une attention particulière aux naines blanches hybrides (qui montrent à la fois des traces d'hydrogène et d'hélium) de notre échantillon et à ce que ces objets distinctifs nous apprennent sur l'évolution spectrale. Nous étudions ensuite l'évolution spectrale d'un point de vue théorique en modélisant les transformations chimiques qui s'opèrent dans les naines blanches. Pour ce faire, nous utilisons le code d'évolution stellaire STELUM, qui inclut un traitement cohérent et réaliste du transport des éléments et nous permet donc de réaliser les simulations numériques d'évolution spectrale les plus sophistiquées à ce jour. Nous modélisons la diffusion de l'hydrogène résiduel dans une enveloppe d'hélium à haute température, qui mène ultimement à la formation d'une atmosphère d'hydrogène. Nous simulons également le mélange convectif de cette couche superficielle d'hydrogène avec la couche sous-jacente d'hélium à basse température, qui produit à nouveau une surface dominée par l'hélium. En outre, nous étudions le transport du carbone dans les étoiles riches en hélium, incluant à la fois le tri gravitationnel à haute température et le dragage convectif à basse température. Ces calculs donnent lieu à plusieurs résultats astrophysiques d'intérêt. Nous obtenons notamment une contrainte inédite sur la quantité d'hydrogène résiduel contenue dans les naines blanches chaudes dominées par l'hélium. Nous démontrons aussi que la bifurcation observée dans le diagramme couleur-magnitude des naines blanches découvertes par le satellite Gaia est une signature du processus de mélange convectif à basse température. Par ailleurs, nos modèles fournissent de précieuses informations sur les propriétés des étoiles polluées par le carbone, en particulier sur leur masse et leur zone convective. Enfin, le résultat le plus important de cette thèse est la résolution définitive du problème le plus sérieux de la théorie de l'évolution spectrale, soit le problème de l'origine de l'hydrogène à la surface des naines blanches de type DBA., This thesis presents an in-depth empirical and theoretical study of the spectral evolution of white dwarf stars, with a particular focus on hot white dwarfs. The atmospheric composition (and thus the spectral appearance) of these stellar remnants can change drastically over time as they cool. This phenomenon is generally interpreted as the result of an interplay between various element transport mechanisms in the stellar envelope (such as diffusion, convection, winds, and accretion), but remains poorly understood in several respects. It is imperative to remedy this situation to be able to exploit the immense potential of white dwarfs for our understanding of the past of the Galaxy. To better characterize the incidence of spectral evolution, we first carry out an exhaustive spectroscopic analysis of nearly 2000 hot white dwarfs (Teff > 30,000 K) observed by the SDSS survey. We determine the atmospheric properties (in particular the effective temperature and surface composition) of these objects using a new set of model atmospheres calculated specifically for this purpose. By examining the relative frequency of hydrogen-rich and helium-rich stars as a function of temperature, we obtain for the first time a detailed empirical picture of the spectral evolution of hot white dwarfs. More specifically, we infer (1) that about one in four stars enters the cooling sequence with a helium atmosphere, and (2) that about two-thirds of these objects eventually develop a hydrogen atmosphere. Furthermore, we pay special attention to the hybrid white dwarfs (which exhibit traces of both hydrogen and helium) in our sample and to what can be learned about spectral evolution from these distinctive objects. We then study spectral evolution from a theoretical point of view by modeling the chemical transformations that take place in white dwarfs. To do this, we use the stellar evolution code STELUM, which includes a consistent and realistic treatment of element transport and therefore allows us to perform the most sophisticated numerical simulations of spectral evolution to date. We model the diffusion of residual hydrogen in a helium envelope at high temperature, which ultimately leads to the formation of a hydrogen atmosphere. We also simulate the convective mixing of this superficial hydrogen layer with the underlying helium layer at low temperature, which once again produces a helium-dominated surface. Furthermore, we study the transport of carbon in helium-rich stars, including both gravitational settling at high temperature and convective dredge-up at low temperature. These calculations give rise to several astrophysical results of interest. In particular, we obtain an unprecedented constraint on the amount of residual hydrogen contained within hot helium-dominated white dwarfs. We also demonstrate that the bifurcation observed in the color-magnitude diagram of white dwarfs discovered by the Gaia satellite is a signature of the convective mixing process at low temperature. Furthermore, our models provide valuable information on the properties of carbon-polluted stars, in particular on their mass and convective zone. Finally, the most important result of this thesis is the definitive resolution of the most serious problem of the theory of spectral evolution, namely the problem of the origin of hydrogen at the surface of DBA-type white dwarfs.

L’objectif principal de cette thèse est de caractériser l’atmosphère de Jupiters chaudes par spectroscopie de transmission à haute résolution, dans l’infrarouge proche, avec l’instrument SPIRou. L’historique de formation, d’évolution et de migration des planètes est empreint dans leur composition chimique, et de retrouver cette composition permet d’en élucider le mystère. La spectroscopie de transit et d’émission a prouvé être fortement efficace à cette tâche, autant pour la détermination de la composition que pour la détermination d’autres caractéristiques atmosphériques comme le profil de température et la dynamique, accessibles à haute résolution. Les Jupiter Chaudes, planètes géantes gazeuses qui orbitent très près de leur étoile, offrent des conditions d’observations très favorables pour ce type d’étude. Encore beaucoup d’éléments nous échappent quant aux processus physiques, chimiques et dynamiques qui gouvernent l’atmosphère de ces objets astronomiques. Des études détaillées de ceux-ci, telles que celles présentées dans cette thèse, sont nécessaires pour mieux comprendre ces mécanismes. Dans un premier temps, nous avons fait l’étude de deux transits de HD 189733 b, une des exoplanètes les plus étudiées. Cela nous a permis de valider nos méthodes d’analyse avec des données provenant du spectropolarimètre infrarouge à haute résolution SPIRou, installé au télescope Canada-France-Hawaii, représentant d’ailleurs la première caractérisation d’une atmosphère en spectroscopie de transit pour le SPIRou Legacy Survey. Nous avons confirmé la présence d’un signal d’eau à un niveau de signification de plus de 5σ, basé sur les résultats de test-t. Nous présentons la première analyse de spectroscopie de transit haute résolution faite par méthode de récupération, basée sur l’inférence bayésienne et appliquée à une grille de modèles SCARLET interpolée. Celle-ci a permis d’inférer une abondance de log_10[H2O] ≃ −4.4. Les résultats obtenus sont cohérents avec la littérature et indiquent que l’atmosphère de HD 189733 b est relativement claire (sans nuages) et possède un C/O super-solaire (correspondant à une formation au-delà de la ligne de glace de l’eau). Un fort décalage vers le bleu de l’absorption par l’eau a été observé, indiquant la présence de forts vents allant du côté jour vers le côté nuit ou un signal dominé par le côté soir du terminateur (limbe arrière), ou une combinaison des deux. Dans un second temps, nous présentons la première analyse à haute résolution dans l’infrarouge proche de trois transits de la très peu dense sous-Saturne WASP-127 b. Une étude récente à basse résolution a montré un spectre de transmission riche et une abondance super-solaire de CO2 dans son atmosphère. La contribution de CO et de CO2 n’a cependant pu être démêlée étant donné la couverture spectrale et la résolution limitée des données HST et de Spitzer utilisées, menant à des scénarios équiprobables de faible et fort C/O. La couverture de la bande de CO à 2.3 μm par SPIRou a permis de faire cette différenciation, et nos résultats ont exclu la présence de CO en abondance supérieure à log_10[CO] = −4.3, impliquant que le signal détecté à 4.5μm dans les données Spitzer provient majoritairement du CO2. De plus, un calcul de test-t sur les données SPIRou a confirmé la détection de H2O à un niveau ajusté de 4.9σ, mais également une détection potentielle de OH, à 2.4σ. Cette présence extrêmement inattendue de OH pourrait potentiellement être expliquée si la température du côté jour est assez grande, aidée par l’irradiation amplifiée de l’étoile qui quitte la séquence principale, ou encore par du mélange vertical. Nous présentons également la première méthode de récupération complète appliquée à la spectroscopie de transit à haute résolution, en utilisant la suite de modèles petitRADTRANS, et sur trois ensembles de données différents : les données SPIRou, les données HST et Spitzer de l’étude initiale, et les deux ensembles de données combinés. Une comparaison des différents résultats obtenus confirme que l’analyse conjointe permet d’avoir de meilleures contraintes sur les paramètres atmosphériques. Alors que l’étude initiale favorisait un fort C/O, nos résultats pointent vers un C/O très sous-solaire, produit par un C/H sous-solaire et un O/H plutôt stellaire. Les scénarios de formation qui supportent une telle composition sont ceux au-delà des lignes de glace de H2O et de CO2 (∼ 10ua), avec une accrétion supplémentaire de matériel riche en O via la migration et le croisement des lignes de glaces. L’accrétion du matériel est soit dominée par le gaz et tardive (après 5 à 7 millions d’années), ou encore, mixte (de gaz et de glaces) et plus précoce, avec un mélange cœur-enveloppe substantiel. Bien qu’il en reste beaucoup à faire, ces travaux de recherche ont démontré que la spectroscopie de transit à haute résolution dans l’infrarouge proche est utile pour explorer les conditions atmosphériques des Jupiter et sous-Saturne chaudes, et plus spécifiquement, avec l’instrument SPIRou. La combinaison de données à faible et à haute résolution s’avère un outil très puissant pour l’étude des atmosphères, et le sera encore plus avec les capacités révolutionnaires de JWST., The main objective of this thesis is to characterize the atmosphere of hot Jupiters with high resolution transmission spectroscopy in the near-infrared with the SPIRou instrument. The formation, evolution and migration history of exoplanets is imprinted in their chemical composition, and finding this composition makes it possible to trace back this history. Transit and emission spectroscopy have proven to be highly effective for this task, in the determination of the composition, but also of other atmospheric characteristics such as the temperature profile and the dynamics, accessible at high resolution. Hot Jupiters -- gas giant planets orbiting very close to their star -- offer highly favourable observation conditions for this type of study. Many pieces of the puzzle are still missing regarding the physical, chemical and dynamical processes that govern the atmospheres of these astronomical objects, and detailed studies, such as the ones presented in this thesis, are necessary to better understand those mechanisms. First, we present the results of our analysis of two HD189733b transits, one of the most studied exoplanets to date. This study allowed to validate our analysis method with SPIRou data, a high-resolution near-infrared spectro-polarimeter installed at the Canada-France-Hawaii Telescope. It also represents the first characterization of an atmosphere with transit spectroscopy as part of the SPIRou Legacy Survey. Our results confirmed the H2O detection in the planet's atmosphere at a 5 sigma level, based on a $t$-test. We present the first analysis of a Bayesian retrieval framework applied to high-resolution transmission spectroscopy, using a grid of SCARLET models. We constrained the H2O abundance to log_10[H2O] ~ -4.4$. The results are consistent with the literature and agree on the atmosphere of HD189733b being relatively clear (without clouds) and having a super-solar C/O (corresponding to a formation beyond the H2O ice line). A strong blue shift of the water absorption signal was observed, indicative of strong day-to-night winds or a signal dominated by the terminator's evening side (trailing limb), or a combination of both. Second, we present the first high-resolution analysis in the near-infrared of three transits of the super low-density sub-Saturn WASP-127b. A recent low-resolution study showed a rich transmission spectrum and super-solar abundance of CO2 in its atmosphere. However, the contribution of CO and CO2 could not be disentangled given the limited spectral coverage and resolution of the HST and Spitzer data, leading to equiprobable low and high C/O scenarios. The coverage of the CO band at 2.3um by SPIRou made it possible to differentiate between the two cases, and our results excluded CO abundances greater than 10^(-4.3), implying that the signal at 4.5um seen in the Spitzer data mostly comes from CO2. Moreover, a t-test analysis on the SPIRou data confirmed the detection of H2O at an adjusted level of 4.9 sigma, but also a tentative detection of OH, at 2.4 sigma. The presence of OH, although extremely unexpected, could potentially be explained from a high enough dayside temperature, increased by the amplified irradiation of the star leaving the main sequence, or from vertical mixing. We also present the first full-retrieval framework applied to transmission spectroscopy at high resolution, using the petitRADTRANS model suite on three different datasets: on the SPIRou data, on the HST and Spitzer data from the original study, and on both datasets combined. A comparison of the different results obtained confirms that the joint analysis provides better constraints on the atmospheric parameters. While the initial study favored a high C/O, our results point toward a highly subsolar C/O, produced by a sub-stellar C/H and a roughly stellar O/H. Formation scenarios that support such a composition are those beyond the H2O and CO2 ice lines (~ 10ua), with further accretion of O-rich material via migration and ice lines crossing. The primordial/bulk accretion was either gas-dominated and late (after 5-7 Myr), or earlier and mixed (with gas and ice), with substantial core-enveloppe mixing. Although much remains to be done, this research work has demonstrated that high-resolution near-infrared transit spectroscopy is useful for exploring the atmospheric conditions of hot Jupiters and sub-Saturns, and more specifically, with the SPIRou instrument. The combination of low and high resolution data has shown to be a very powerful tool for such studies, and will be even more so with the revolutionary capabilities of JWST.

We investigate the origin of the measured over-abundance of alkali metals in the atmospheres of hot gas giants, relative to both their host stars and their atmospheric water abundances. We show that formation exterior to the water snow line followed by inward disc-driven migration results in excess accretion of oxygen-poor, refractory-rich material from within the snow-line. This naturally leads to enrichment of alkali metals in the planetary atmosphere relative to the bulk composition of its host star but relative abundances of water that are similar to the stellar host. These relative abundances cannot be explained by in situ formation which places the refractory elements in the planetary deep interior rather than the atmosphere. We therefore suggest that the measured compositions of the atmospheres of hot Jupiters are consistent with significant migration for at least a subset of hot gas giants. Our model makes robust predictions about atmospheric composition that can be confirmed with future data from JWST and Ariel., 10 pages, 5 figures, 1 table, accepted for publication in MNRAS

著者人数: 60名, 形態: カラー図版あり, Number of authors: 60, Physical characteristics: Original contains color illustrations, Accepted: 2021-08-18, 資料番号: PA2210074000

Various interventions were made by the Thai government to prevent the COVID-19 spread by controlling socioeconomic activities, but the effectiveness of these interventions and other factors have not yet been fully clarified. Thus, this study aims to provide further scientific evidence on those potential factors which affect the socioeconomic activities changes during the pandemic, by using spatial analysis on atmospheric composition. By taking Phra Nakhon Si Ayutthaya Province, Thailand as the case area. Results of the government's COVID-19 measures and statuses of industries were compared with changes in aerosols, including PM 2.5 which was analyzed by Google Earth Engine with nine open datasets including meteorological and hydrological factors. The analysis revealed that the aerosol index in ueban area of the province decreased at 28.03% in 2020 compared in 2019. Besides, PM 2.5 drastically decreased from March 2020, even without the influence of wind speed which as the highest causal relationship, and kept low level compared with previous years. The reason of the tendency would be explained that other than government interventions including national-level state of the emergency decree, reduction of factories' activities at Rojana Industrial Park and reduction of the number of tourists had significant influence to reduce the mean value of PM 2.5.

Starting in 1969 and comprising three launches a week, the Uccle (Brussels, Belgium) ozonesonde dataset is one of longest and densest in the world. Moreover, as the only major change was the switch from Brewer-Mast (BM) to electrochemical concentration cell (ECC) ozonesonde types in 1997 (when the emissions of ozone-depleting substances peaked), the Uccle time series is very homogenous. In this paper, we briefly describe the efforts that were undertaken during the first 3 decades of the 50 years of ozonesonde observations to guarantee the homogeneity between ascent and descent profiles, under changing environmental conditions (e.g. SO2), and between the different ozonesonde types. This paper focuses on the 50-year-long Uccle ozonesonde dataset and aims to demonstrate its past, present, and future relevance to ozone research in two application areas: (i) the assessment of the temporal evolution of ozone from the surface to the (middle) stratosphere, and (ii) as the backbone for validation and stability analysis of both stratospheric and tropospheric satellite ozone retrievals. Using the Long-term Ozone Trends and Uncertainties in the Stratosphere (LOTUS) multiple linear regression model (SPARC/IO3C/GAW, 2019), we found that the stratospheric ozone concentrations at Uccle have declined at a significant rate of around 2 % per decade since 1969, which is also rather consistent over the different stratospheric levels. This overall decrease can mainly be assigned to the 1969–1996 period with a rather consistent rate of decrease of around −4 % per decade. Since 2000, a recovery of between +1 % per decade and +3 % per decade of the stratospheric ozone levels above Uccle has been observed, although it is not significant and is not seen for the upper stratospheric levels measured by ozonesondes. Throughout the entire free troposphere, a very consistent increase in the ozone concentrations of 2 % per decade to 3 % per decade has been measured since both 1969 and 1995, with the trend since 1995 being in almost perfect agreement with the trends derived from the In-service Aircraft for a Global Observing System (IAGOS) ascent/descent profiles at Frankfurt. As the number of tropopause folding events in the Uccle time series has increased significantly over time, increased stratosphere-to-troposphere transport of recovering stratospheric ozone might partly explain these increasing tropospheric ozone concentrations, despite the levelling-off of (tropospheric) ozone precursor emissions and notwithstanding the continued increase in mean surface ozone concentrations. Furthermore, we illustrate the crucial role of ozonesonde measurements for the validation of satellite ozone profile retrievals. With the operational validation of the Global Ozone Monitoring Experiment-2 (GOME-2), we show how the Uccle dataset can be used to evaluate the performance of a degradation correction for the MetOp-A/GOME-2 UV (ultraviolet) sensors. In another example, we illustrate that the Microwave Limb Sounder (MLS) overpass ozone profiles in the stratosphere agree within ±5 % with the Uccle ozone profiles between 10 and 70 hPa. Another instrument on the same Aura satellite platform, the Tropospheric Emission Spectrometer (TES), is generally positively biased with respect to the Uccle ozonesondes in the troposphere by up to ∼ 10 ppbv, corresponding to relative differences of up to ∼ 15 %. Using the Uccle ozonesonde time series as a reference, we also demonstrate that the temporal stability of those last two satellite retrievals is excellent.

Iran is a semi-arid and arid country in Western Asia and is exposed to numerous local and trans-regional dust systems due to its location in the global dust belt. The present study sought to investigate the change-point detection (CPD) and trend of the number of dusty hours (NDH) in Iran over a long-term period (1980–2015). The station dust frequency (SDF) of 81 synoptic stations was first hourly obtained and then processed. Furthermore, the dust aerosol optical depth (DOD) was obtained hourly from the Monitoring Atmospheric Composition and Climate (MACC). The results indicated the maximum dust frequency with 21.28 days at 12 GMT due to surface heating and the occurrence of local dry instabilities. The minimum dust also occurred with 7.76 days at 00 GMT in Iran. SDF and DOD had a direct relationship, but they had inverse significant relationships with altitude and latitude in Iran. The maximum average trend of the whole of Iran at 21 GMT with a value of Z 1.83 was significant at a 90% level, indicating an increase in nocturnal dust in Iran. The southwest of Iran, especially Bostan, Omidiyeh, and Masjed-Soleyman stations, had maximum numbers of dusty days so that NDHs of Omidiyeh station were increasing at 18 GMT (2.84 years−1 days). The year 2000 was, on area-averaged, the dust CPD in the across Iran, but 2007 and 2008 were the most frequent CPD of NDHs. None of the hours had lower amounts of dust after the CPD than before the CPD, indicating a significant increase in the dust of Iran.

Accurate knowledge of cloud properties is essential to the measurement of atmospheric composition from space. In this work we assess the quality of the cloud data from three Copernicus Sentinel-5 Precursor (S5P) TROPOMI cloud products: (i) S5P OCRA/ROCINN_CAL (Optical Cloud Recognition Algorithm/Retrieval of Cloud Information using Neural Networks;Clouds-As-Layers), (ii) S5P OCRA/ROCINN_CRB (Clouds-as-Reflecting Boundaries), and (iii) S5P FRESCO-S (Fast Retrieval Scheme for Clouds from Oxygen absorption bands – Sentinel). Target properties of this work are cloud-top height and cloud optical thickness (OCRA/ROCINN_CAL), cloud height (OCRA/ROCINN_CRB and FRESCO-S), and radiometric cloud fraction (all three algorithms). The analysis combines (i) the examination of cloud maps for artificial geographical patterns, (ii) the comparison to other satellite cloud data (MODIS, NPP-VIIRS, and OMI O2–O2), and (iii) ground-based validation with respect to correlative observations (30 April 2018 to 27 February 2020) from the Cloudnet network of ceilometers, lidars, and radars. Zonal mean latitudinal variation of S5P cloud properties is similar to that of other satellite data. S5P OCRA/ROCINN_CAL agrees well with NPP VIIRS cloud-top height and cloud optical thickness and with Cloudnet cloud-top height, especially for the low (mostly liquid) clouds. For the high clouds, S5P OCRA/ROCINN_CAL cloud-top height is below the cloud-top height of VIIRS and of Cloudnet, while its cloud optical thickness is higher than that of VIIRS. S5P OCRA/ROCINN_CRB and S5P FRESCO cloud height are well below the Cloudnet cloud mean height for the low clouds but match on average better with the Cloudnet cloud mean height for the higher clouds. As opposed to S5P OCRA/ROCINN_CRB and S5P FRESCO, S5P OCRA/ROCINN_CAL is well able to match the lowest CTH mode of the Cloudnet observations. Peculiar geographical patterns are identified in the cloud products and will be mitigated in future releases of the cloud data products.

Results obtained in the course of unique observations (as part of the TROICA project) of the composition and state of the atmosphere over Russia have been summarized. Scientists and engineers from different countries took part in these observations. The main task of these observations was to measure atmospheric contents of trace gases and aerosols and both meteorological and radiative characteristics of the atmosphere using a mobile laboratory designed and brought into operation specially for transcontinental observations along the network of Russian electrified railroads. A large database obtained in the TROICA experiments using the mobile laboratory, in field experiments, and at scientific stations is still under analysis. In this work, the most important results published earlier and obtained recently are discussed, which makes it possible to form a comprehensive picture of the spatial distribution and temporal variability of the atmospheric composition over northern Eurasia.

This paper presents the results of a comprehensive analysis of measurements of CO total content (CO TC) at stations of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS), in Moscow and Moscow oblast. Also CO in-situ data obtained from automated stations of the Mosecomonitoring network, satellite monitoring results and information on the parameters of the atmospheric boundary layer in Moscow and the surrounding regions are analyzed. The long-term variability of CO TC and meteorological parameters is investigated, the carbon monoxide accumulation characteristics in calm days in the atmospheric boundary layer are obtained. A decrease in the average annual values ​​of TC CO in 2000–2018 was found in Moscow (–2.56 ± 0.52%/year) and at the Zvenigorod Scientific Station (ZSS) (‒1.15 ± 0.37%/year). However, the rate of decrease in both sites is different in different seasons and periods. After about 2007–2008, the rate of CO TC reduction decreased at both sites. In 2008–2018, at the ZSS, an increase in CO TC was recorded in the summer and autumn months at a rate of about 0.7%/year. An increase in the wind speed in the atmospheric boundary layer of Moscow in different periods of 2000–2018 at a rate of 0.4–1.6%/year has been determined. At the same time, no statistically significant changes in wind speed were found in Kaluga oblast. The recurrence of calm days in Moscow in 2006–2017 decreased (–7.06 ± 3.96%/year) with a decrease in the anthropogenic part of the CO content in the same period (–6.72 ± 3.48%/year). The results indicate the influence of the climatic (meteorological) factor on air quality in Moscow.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., Using the Nadir and Occultation for MArs Discovery instrument aboard Trace Gas Orbiter, we derived the CO/CO2 profiles between 75 and 105 km altitude with the equivalent width technique. The derived CO/CO2 profiles showed significant seasonal variations in the southern hemisphere with decreases near perihelion and increases near aphelion. The estimation of the CO/CO2 profiles with a one-dimensional photochemical model shows that an altitude-dependent eddy diffusion coefficient better reproduces the observed profiles than a vertically uniform one. Our estimation suggests that the eddy diffusion coefficient in Ls = 240–270 is uniformly larger by a factor of ∼2 than that in Ls = 90–120 in the southern hemisphere, while they are comparable in the northern hemisphere. This fact demonstrates that the eddy diffusion coefficient is variable with season and latitude. © 2022. The Authors., The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493), by Spanish Ministry of Science and Innovation (MCIU) and by European funds under Grants PGC2018-101836-B-I00 and ESP2017-87143-R (MINECO/FEDER), as well as by UK Space Agency through Grants ST/V002295/1, ST/V005332/1, and ST/S00145x/1 and Italian Space Agency through Grant 2018-2-HH.0. This work was supported by the Belgian Fonds de la Recherche Scientifique–FNRS under Grant No. 30442502 (ET_HOME). The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). US investigators were supported by the National Aeronautics and Space Administration. Canadian investigators were supported by the Canadian Space Agency. Y. N. is supported by The international Joint Graduate Program in Earth and Environmental Sciences, Tohoku University (GP-EES), and the Japanese Society for the Promotion of Science (JP21J13710). This work was supported by JSPS KAKENHI Grant Nos. 20H04605 and 19K03943.

Accurate measurements of a planet's mass, radius and age (provided for example by the PLATO mission and follow-up measurements) together with compositional constraints from the stellar spectrum can help us to deduce potential evolutionary pathways that rocky planets can evolve along, and allow us to predict the range of likely atmospheric properties that can then be compared to observations.However, for the evolution of composition and mass of an atmosphere, a large degeneracy exists due to several planetary and exterior factors and processes, making it very difficult to link the interior (and hence outgassing processes) of a planet to its atmosphere. The community therefore thrives now to identify the key factors that impact an atmosphere, and that may lead to distinguishable traces in planetary, secondary outgassed atmospheres. Such key factors are for example the planetary mass (impacting atmospheric erosion processes) or surface temperature (impacting atmospheric chemistry, weathering and interior-atmosphere interactions).Here we investigate the signature that a planet evolving into plate tectonics leaves in its atmophere due to its impact on volcanic outgassing fluxes and volatile releases to the atmosphere - leading possibly to distinguishable sets of atmospheric compositions for stagnant-lid planets and plate tectonics planets. These preliminary findings will need to be further investigated with coupled atmosphere-interior models including various feedback mechanisms such as condensation and weathering as well as atmospheric escape to space.

Relating planet formation to atmospheric composition has been a long-standing goal of the planetary science community. So far, most modeling studies have focused on predicting the enrichment of heavy elements and the C/O ratio in giant planet atmospheres. Although this framework provides useful constraints on the potential formation locations of gas giant exoplanets, carbon and oxygen measurements alone are not enough to determine where a given gas giant planet originated. Here, we show that characterizing the abundances of refractory elements (e.g., silicon, iron) can break these degeneracies. Refractory elements are present in the solid phase throughout most of the disk and their atmospheric abundances therefore reflect the solid-to-gas accretion ratio during formation. We introduce a new framework that parameterizes the atmospheric abundances of gas giant exoplanets in the form of three ratios: Si/H, O/Si, and C/Si. Si/H traces the solid-to-gas accretion ratio of a planet and is loosely equivalent to earlier notions of 'metallicity'. For O/Si and C/Si, we present a global picture of their variation with distance and time based on what we know from the solar system meteorites and an updated understanding of the variations of thermal processing within protoplanetary disks. We show that ultra-hot Jupiters are ideal targets for atmospheric characterization studies using this framework, as we can measure the abundances of refractories, oxygen and carbon in the gas phase. Finally, we propose that hot Jupiters with silicate clouds and low water abundances might have accreted their envelopes between the soot line and the water snowline., Comment: accepted to ApJ on Nov 22, 2022. Added DOI and journal ref

International audience; The 3 IASI instruments on-board the Metop satellites have been sounding the atmospheric composition since 2006. Up to ~30 atmospheric gases can be measured from IASI spectra, allowing the improvement of weather forecasting, and the analysis and monitoring of atmospheric chemistry and climate variables.The early detection of extreme events such as fires, pollution episodes, volcanic eruptions, industrial accidents, is key to take appropriate decisions regarding safety to protect inhabitants and the environment in the target areas. With IASI providing global observations twice a day in near real time, a new way for the systematic and continuous detection of exceptional atmospheric events to support operational decisions is possible.In this work, we explore and improve a method for the detection and characterization of extreme events using the recorded spectra, which relies on the principal component analysis (PCA) method. We assess this PCA-based system by analysing IASI raw and reconstructed spectra along with their differences (residuals) for various past and documented extreme events. The benefits and limitations of this approach are discussed with comparison with available CO and SO2 IASI products. A methodological innovation, based on the refined analysis of extreme residuals (outliers) for the detection of fires, volcanic eruptions and pollution event is proposed, and could be used for the automatic and systematic detection of unexpected events.

The recently adopted Ariel ESA mission will measure the atmospheric composition of a large number of exoplanets. This information will then be used to better constrain planetary bulk compositions. While the connection between the composition of a planetary atmosphere and the bulk interior is still being investigated, the combination of the atmospheric composition with the measured mass and radius of exoplanets will push the field of exoplanet characterisation to the next level, and provide new insights of the nature of planets in our galaxy. In this white paper, we outline the ongoing activities of the interior working group of the Ariel mission, and list the desirable theoretical developments as well as the challenges in linking planetary atmospheres, bulk composition and interior structure., Experimental Astronomy, 53, ISSN:0922-6435, ISSN:1572-9508

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made., The goal of the Ariel space mission is to observe a large and diversified population of transiting planets around a range of host star types to collect information on their atmospheric composition. The planetary bulk and atmospheric compositions bear the marks of the way the planets formed: Ariel’s observations will therefore provide an unprecedented wealth of data to advance our understanding of planet formation in our Galaxy. A number of environmental and evolutionary factors, however, can affect the final atmospheric composition. Here we provide a concise overview of which factors and effects of the star and planet formation processes can shape the atmospheric compositions that will be observed by Ariel, and highlight how Ariel’s characteristics make this mission optimally suited to address this very complex problem. © The Author(s) 2021., D.T., S.F., S.M., E.S., and A.N. acknowledge the support of the Italian Space Agency (ASI) through the ASI-INAF contract 2018-22-HH.0. D.T., C.C., D.F., and L.P. acknowledge the support of the PRIN-INAF 2016 “The Cradle of Life - GENESIS-SKA (General Conditions in Early Planetary Systems for the rise of life with SKA”. D.T., S.F., S.M. D.F, J.M., F.O., P.W. acknowledge the support of the Italian National Institute of Astrophysics (INAF) through the INAF Main Stream project “Ariel and the astrochemical link between circumstellar discs and planets” (CUP: C54I19000700005). S.M. acknowledges support from the European Research Council via the Horizon 2020 Framework Programme ERC Synergy “ECOGAL” Project GA-855130. M.K. acknowledges funding by the University of Tartu ASTRA project 2014-2020.4.01.16-0029 KOMEET “Benefits for Estonian Society from Space Research and Application”, financed by the EU European Regional Development Fund. J.M.D.K. gratefully acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through an Emmy Noether Research Group (grant number KR4801/1-1) and the DFG Sachbeihilfe (grant number KR4801/2-1), as well as from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme via the ERC Starting Grant MUSTANG (grant agreement number 714907). The research of O.P. is funded by the Royal Society, through Royal Society Dorothy Hodgkin Fellowship DH140243. M.P. thanks the support to NuGrid from STFC (through the University of Hull’s Consolidated Grant ST/R000840/1), and access to VIPER, the University of Hull High Performance Computing Facility. M.P. acknowledges the support from the ”Lendulet-2014” Program of the Hungarian Academy of Sciences (Hungary), from the ERC Consolidator Grant (Hungary) funding scheme (Project RADIOSTAR, G.A. n. 724560), by the National Science Foundation (NSF, USA) under grant No. PHY-1430152 (JINA Center for the Evolution of the Elements). M.P. also thanks the UK network BRIDGCE and the ChETEC COST Action (CA16117), supported by COST (European Cooperation in Science and Technology). M.I. thanks the support by JSPS KAKENHI 18H05439. C.D. acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709), and the Group project Ref. PID2019-110689RB-I00/AEI/10.13039/501100011033.

Dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Geospatial Technologies Satellite and model atmospheric composition data are stored in different platforms, using heterogeneous file formats, varying spatiotemporal resolutions and noncompatible metadata. Comparing these datasets is not a trivial task, but required in data assimilation, validation and mutual coverage studies. This thesis investigates the prevailing methods used to compare sensor observations with data from the forecast and reanalysis system developed by the Copernicus Atmospheric Monitoring Service (CAMS). These are implemented in the development of the first prototype of the Atmospheric Datasets Comparison (ADC) Toolbox. This toolbox, which is the core part of the project, contains a set of tools that facilitate the file interoperability, binning and regridding, computation of levels pressure, conversion of units, application of the averaging kernels, datasets merge, geostatistical comparison and trend analysis. The contribution of this work is twofold: a toolbox is developed to merge and compare atmospheric composition datasets systematic and automatically for any region and time, and its applicability is shown in a case study, where the NO2 emissions in Spain in the last decade are analyzed using satellite and model data.

We present the results of a large-scale study of carbon dioxide and methane distributions carried out on the territory of Western Siberia in 2018–2019 using a Picarro G4301 portable gas analyzer. The analysis of the data made it possible to retrieve the spatial distribution of background CO2 and CH4 concentrations with a high resolution. The inhomogeneities found in the CO2 and CH4 distributions were both due to the effect of ecosystems characteristic for different regions of Western Siberia and to specific features of their seasonal cycles.

Fires affect the composition of the atmosphere and Earth's radiation balance by emitting a suite of reactive gases and particles. An interactive fire module in an Earth system model (ESM) allows us to study the natural and anthropogenic drivers, feedbacks, and interactions of open fires. To do so, we have developed pyrE, the NASA GISS (Goddard Institute for Space Studies) interactive fire emissions module. The pyrE module is driven by environmental variables like flammability and cloud-to-ground lightning, calculated by the GISS ModelE ESM, and parameterized by anthropogenic impacts based on population density data. Fire emissions are generated from the flaming phase in pyrE (active fires). Using pyrE, we examine fire occurrence, regional fire suppression, burned area, fire emissions, and how it all affects atmospheric composition. To do so, we evaluate pyrE by comparing it to satellite-based datasets of fire count, burned area, fire emissions, and aerosol optical depth (AOD). We demonstrate pyrE's ability to simulate the daily and seasonal cycles of open fires and resulting emissions. Our results indicate that interactive fire emissions are biased low by 32 %–42 %, depending on emitted species, compared to the GFED4s (Global Fire Emissions Database) inventory. The bias in emissions drives underestimation in column densities, which is diluted by natural and anthropogenic emissions sources and production and loss mechanisms. Regionally, the resulting AOD of a simulation with interactive fire emissions is underestimated mostly over Indonesia compared to a simulation with GFED4s emissions and to MODIS AOD. In other parts of the world pyrE's performance in terms of AOD is marginal to a simulation with prescribed fire emissions.

This study presents a high-precision method, using a preconcentrator–gas chromatograph with microelectron capture detector (GC-μECD), to measure SF6 at ambient levels. Carboxen 1000 was used as an adsorbent for the preconcentrator and exhibited a high adsorption efficiency for N2O and SF6 and low adsorption efficiency for O2. This enabled the selective removal of atmospheric O2 from analytes and improved repeatability of the SF6 peak that followed the O2 peak, in a separation column of activated alumina F1. In addition, the increased sensitivity resulting from preconcentrated SF6 improved the signal-to-noise ratio. This led to better analytical precision in comparison with other measurement methods including the conventional and forecut–backflush (FCBF) methods. The precision-to-drift ratios of the conventional, FCBF, and preconcentration methods were 0.11, 0.10, and 0.03, respectively. Analytical precision of the preconcentration method was 0.08% for 10 consecutive injections; this was the best among the three methods. The long-term drift of the SF6 response was inversely proportional to the laboratory pressure. Based on this finding, room pressure can be used to correct for ECD signal drift, with an uncertainty of 0.14% over a 48-h period, using the preconcentration method. Another advantage of the preconcentration method was the excellent linearity of the SF6 response to a wide range of concentrations, including its ambient concentration.

Multi-axis differential optical absorption spectroscopy (MAX-DOAS) tropospheric NO2 column retrievals from four European measurement stations are compared to simulations from five regional air quality models which contribute to the European regional ensemble forecasts and reanalyses of the operational Copernicus Atmosphere Monitoring Service (CAMS). Compared to other observational data usually applied for regional model evaluation, MAX-DOAS data are closer to the regional model data in terms of horizontal and vertical resolution, and multiple measurements are available during daylight, so that, for example, diurnal cycles of trace gases can be investigated.In general, there is good agreement between simulated and retrieved NO2 column values for individual MAX-DOAS measurements with correlations between 35% and 70% for individual models and 45% to 75% for the ensemble median for tropospheric NO2 vertical column densities (VCDs), indicating that emissions, transport and tropospheric chemistry of NOx are on average well simulated. However, large differences are found for individual pollution plumes observed by MAX-DOAS. Most of the models overestimate seasonal cycles for the majority of MAX-DOAS sites investigated. At the urban stations, weekly cycles are reproduced well, but the decrease towards the weekend is underestimated and diurnal cycles are overall not well represented. In particular, simulated morning rush hour peaks are not confirmed by MAX-DOAS retrievals, and models fail to reproduce observed changes in diurnal cycles for weekdays versus weekends. The results of this study show that future model development needs to concentrate on improving representation of diurnal cycles and associated temporal scalings.

This review contains the most important results obtained by Russian scientists in studying atmospheric ozone in 2015–2018 and is a part of the Russian National Report on Meteorology and Atmospheric Sciences that was prepared for the International Association of Meteorology and Atmospheric Sciences (IAMAS). This report was considered and approved at the 27th General Assembly of the International Union of Geodesy and Geophysics (IUGG). A list of main Russian publications on atmospheric ozone and its precursors is appended to it.

Due to its surrounding strong and deep Asian summer monsoon (ASM) circulation and active surface pollutant emissions, surface pollutants are transported to the stratosphere from the Tibetan Plateau region, which may have critical impacts on global climate through chemical, microphysical and radiative processes. This article reviews major recent advances in research regarding troposphere–stratosphere transport from the region of the Tibetan Plateau. Since the discovery of the total ozone valley over the Tibetan Plateau in summer from satellite observations in the early 1990s, new satellite-borne instruments have become operational and have provided significant new information on atmospheric composition. In addition, in situ measurements and model simulations are used to investigate deep convection and the ASM anticyclone, surface sources and pathways, atmospheric chemical transformations and the impact on global climate. Also challenges are discussed for further understanding critical questions on microphysics and microchemistry in clouds during the pathway to the global stratosphere over the Tibetan Plateau.

The importance of and interest to research and investigations of atmospheric composition and its modeling for different applications are substantially increased. Air quality forecast (AQF) and assessment systems help decision makers to improve air quality and public health, mitigate the occurrence of acute air pollution episodes, particularly in urban areas, and reduce the associated impacts on agriculture, ecosystems and climate. Advanced approaches in AQF combine an ensemble of state-of-the-art models, high-resolution emission inventories, satellite observations, and surface measurements of most relevant chemical species to provide hindcasts, analyses, and forecasts from global to regional air pollution and downscaling for selected countries, regions, and urban areas. Based on published reviews and recent analyses, the article discusses main gaps, challenges, applications and advances, main trends and research needs in further advancements of atmospheric composition and air quality modeling and forecasting.

Chemical compositions of exoplanets can provide key insights into their physical processes, and formation and evolutionary histories. Atmospheric spectroscopy provides a direct avenue to probe exoplanetary compositions. However, whether obtained in transit or thermal emission, spectroscopic observations probe limited pressure windows of planetary atmospheres and are directly sensitive to only a limited set of spectroscopically active species. It is therefore critical to have chemical models that can relate retrieved atmospheric compositions to an atmosphere's bulk physical and chemical state. To this end we present Levi, a chemical kinetics code for modelling exoplanetary atmospheres. Levi is constructed as a eulerian solver of a series of coupled 1-D continuity equations for the evolution of molecular species. Levi is able to calculate the gas phase hydrogen, oxygen, carbon, and nitrogen chemistry in hot Jupiters to produce abundance profiles of the planets��� atmospheres. We perform extensive testing of Levi to ensure its accuracy, including investigations of how both the boundary and initial conditions of the model could affect the final result, as well as comparing the thermochemical processes to the diffusional and photochemical processes. Levi underwent benchmarking by testing it against already existing codes of the same type, to ensure the code was consistent with previously produced models. We use Levi to run a suite of models across a range of metallicities to produce the abundance of a number of molecules in any hot Jupiter's atmosphere. Our parameter sweep covers metallicities between 0.1x and 10x solar values for the C/H, O/H and N/H ratios, and equilibrium temperatures of hot Jupiters between 1000K and 2000K. We link this parameter sweep to hot Jupiter formation and migration models from previous works to produce predictions of the link between molecular abundance and planet formation pathways, for the spectrally active molecules H2O, CO, CH4, CO2, HCN and NH3. We investigate the detections of numerous molecules in the atmosphere of HD 209458b, and find that within the framework of our model, the abundance of these molecules best matches with a planet that formed by gravitational instability between the CO2 and CO snowlines and underwent disk-free migration to reach its current location. We next extend the underlying chemical network used in Levi. We present and validate a new network of atmospheric thermo-chemical and photo-chemical sulfur reactions. Sulfur was chosen as the element to add due to its importance on planets such as Venus and the existence of previous studies that have shown that sulfur may be significant in hot Jupiter atmospheres. We use Levi to investigate these reactions as part of a broader HCNO chemical network in a series of hot and warm Jupiters. We also investigate how the inclusion of sulfur can manifest in a hot Jupiter's atmosphere indirectly. Sulfur chemistry can result in the depletion of many non-sulfur-bearing species, including CH4, NH3 and HCN, by several orders of magnitude. In summary, we create a 1-D photochemical-kinetic model and show that it can be used to constrain the dynamics of exoplanet atmospheres and their origins. Some of the key directions for future development include expanding the sophistication of the underlying chemical networks, work begun by our introduction of sulfur, and exploring the possibility of 2-D and 3-D dynamical models, to account for zonal redistribution. More developed chemical networks allow us to better constrain the atmospheric chemistry, and thus the overall atmospheric composition, breaking existing degeneracies we highlight, while improving the treatment of the dynamics ensures our modelling gives a more accurate depiction of the disequilibrium chemistry taking place.

Der Ausbruch des Eyjafjallajökull in Island 2010 zeigte eindrucksvoll, welche Folgen ein Vulkanausbruch für den internationalen Luftverkehr haben kann. Mehr als 100.000 Flüge wurden gestrichen, da vulkanisches Aerosol eine Gefahr für Flugzeuge darstellt. Aus diesem Grund sind die Flugsicherung sowie Fluggesellschaften sehr an zuverlässigen Vorhersagen der Ausbreitung dieses Aerosols nach Vulkanausbrüchen interessiert. Die numerische Aerosolausbreitungsvorhersage ist ein klassisches Anfangswertproblem. Das bedeutet erstens, dass die Vorhersage mit einem möglichst genauen atmosphärischen Zustand sowie deren Zusammensetzung initialisiert werden muss. Zweitens muss das numerische Modell alle Prozesse und Rückkopplungsmechanismen berücksichtigen, welche für den Transport vulkanischer Aerosole relevant sind. Im Rahmen dieser Arbeit möchte ich die Ausbreitungsvorhersage vulkanischer Aerosole mit Hilfe einer En-Var Datenassimilation sowie durch die Berücksichtigung der Aerosol-Strahlung-Wechselwirkung von intern gemischtem Aerosol verbessern. Hierfür werden in das ICON-ART (ICOsahedral Nonhydrostatic - Aerosols and Reactive Trace gases) Modell aerosol-dynamische Prozesse wie die Koagulation, die Nukleation von Sulfatpartikeln und der Kondensation von gasförmigen Komponenten auf Aerosolpartikel implementiert. Diese mikrophysikalischen Prozesse bilden intern gemischte Partikel. Für diese intern gemischten Partikel bestimme ich optische Eigenschaften, welche eine Interaktion mit kurz- und langwelliger Strahlung ermöglichen. Darüber hinaus wird eine En-Var-Datenassimilationsmethode für vulkanisches Aerosol innerhalb der Datenassimilationsumgebung des DWD (Deutscher Wetterdienst) entwickelt. Die Datenassimilation liefert eine Schätzung des anfänglichen Zustands sowie der Zusammensetzung der Atmosphäre. Diese Neuentwicklungen werden für die ersten vier Tage nach dem Raikoke-Ausbruch 2019, einem der größten Vulkanausbrüche der vergangenen 30 Jahre, ausgewertet. Die Berücksichtigung aerosol-dynamischer Prozesse führt zu einer Zunahme der Partikelgröße, was deren Sedimentationsgeschwindigkeit erhöht. Meine Ergebnisse zeigen, dass die Sedimentation großer Partikel für die Beseitigung von etwa $50$% der Vulkanasche während der ersten $12$ h nach dem Ausbruch des Raikoke verantwortlich ist. In meinen Simulationen ist die Koagulation von grobkörnigen (coarse mode) Aschepartikeln mit sekundärem vulkanischem Aerosol, d.h. Sulfatpartikeln, eine der Hauptursachen für diese hohe Abnahme. Die Wechselwirkung von kurz- und langwelliger Strahlung mit intern gemischtem vulkanischem Aerosol führt zu einem Anheben von Teilen der Wolke aus vulkanischen Aerosolen. Meine Ergebnisse deuten darauf hin, dass die Wolkenoberseite des vulkanischen Aerosols nach dem Ausbruch des Raikoke während der ersten $12$ h etwa $3$ km angehoben wird und nach vier Tagen eine Höhe von etwa $20$ km erreicht. Die Assimilation von Beobachtungsdaten mit der ART En-Var-Methode kann Rauschen in den Beobachtungsdaten herausfiltern. Die Ergebnisse dieser Arbeit verdeutlichen die Bedeutung der aerosol-dynamischen Prozesse sowie der Wechselwirkung von Aerosolen mit kurz- und langwelliger Strahlung für die operationelle Ausbreitungsvorhersage vulkanischer Aerosole. Darüber hinaus kann die Verwendung einer ensemblebasierten Assimilationsmethode für zukünftige Ausbreitungsvorhersagen vulkanischer Aerosole empfohlen werden.

During spring 2020, the COVID-19 pandemic caused massive reductions in emissions from industry and ground and airborne transportation. To explore the resulting atmospheric composition changes, we conducted the BLUESKY campaign with two research aircraft and measured trace gases, aerosols, and cloud properties from the boundary layer to the lower stratosphere. From 16 May to 9 June 2020, we performed 20 flights in the early COVID-19 lockdown phase over Europe and the Atlantic Ocean. We found up to 50% reductions in boundary layer nitrogen dioxide concentrations in urban areas from GOME-2B satellite data, along with carbon monoxide reductions in the pollution hot spots. We measured 20%-70% reductions in total reactive nitrogen, carbon monoxide, and fine mode aerosol concentration in profiles over German cities compared to a 10-yr dataset from passenger aircraft. The total aerosol mass was significantly reduced below 5 km altitude, and the organic aerosol fraction also aloft, indicative of decreased organic precursor gas emissions. The reduced aerosol optical thickness caused a perceptible shift in sky color toward the blue part of the spectrum (hence BLUESKY) and increased shortwave radiation at the surface. We find that the 80% decline in air traffic led to substantial reductions in nitrogen oxides at cruise altitudes, in contrail cover, and in resulting radiative forcing. The light extinction and depolarization by cirrus were also reduced in regions with substantially decreased air traffic. General circulation-chemistry model simulations indicate good agreement with the measurements when applying a reduced emission scenario. The comprehensive BLUESKY dataset documents the major impact of anthropogenic emissions on the atmospheric composition.

Satellite measurements in nadir and limb viewing geometry provide a complementary view of the atmosphere. An effective combination of the limb and nadir measurements can give new information about atmospheric composition. In this work, we present tropospheric ozone column datasets that have been created using a combination of total ozone columns from OMI (Ozone Monitoring Instrument) and TROPOMI (TROPOspheric Monitoring Instrument) with stratospheric ozone column datasets from several available limb-viewing instruments: MLS (Microwave Limb Sounder), OSIRIS (Optical Spectrograph and InfraRed Imaging System), MIPAS (Michelson Interferometer for Passive Atmospheric Sounding), SCIAMACHY (SCanning Imaging Spectrometer for Atmospheric CHartographY), OMPS-LP (Ozone Mapping and Profiles Suite – Limb Profiler), and GOMOS (Global Ozone Monitoring by Occultation of Stars). We have developed further the methodological aspects of the assessment of tropospheric ozone using the residual method supported by simulations with the chemistry transport model SILAM (System for Integrated modeLling of Atmospheric coMposition). It has been shown that the accurate assessment of ozone in the upper troposphere and the lower stratosphere (UTLS) is of high importance for detecting the ground-level ozone patterns. The stratospheric ozone column is derived from a combination of ozone profiles from several satellite instruments in limb-viewing geometry. We developed a method for the data homogenization, which includes the removal of biases and a posteriori estimation of random uncertainties, thus making the data from different instruments compatible with each other. The high-horizontal- and vertical-resolution dataset of ozone profiles is created via interpolation of the limb profiles from each day to a 1∘×1∘ horizonal grid. A new kriging-type interpolation method, which takes into account data uncertainties and the information about natural ozone variations from the SILAM-adjusted ozone field, has been developed. To mitigate the limited accuracy and coverage of the limb profile data in the UTLS, a smooth transition to the model data is applied below the tropopause. This allows for the estimation of the stratospheric ozone column with full coverage of the UTLS. The derived ozone profiles are in very good agreement with collocated ozonesonde measurements. The residual method was successfully applied to OMI and TROPOMI clear-sky total ozone data in combination with the stratospheric ozone column from the developed high-resolution limb profile dataset. The resulting tropospheric ozone column is in very good agreement with other satellite data. The global distributions of tropospheric ozone exhibit enhancements associated with the regions of high tropospheric ozone production. The main datasets created are (i) a monthly 1∘×1∘ global tropospheric ozone column dataset (from ground to 3 km below the tropopause) using OMI and limb instruments, (ii) a monthly 1∘×1∘ global tropospheric ozone column dataset using TROPOMI and limb instruments, and (iii) a daily 1∘×1∘ interpolated stratospheric ozone column from limb instruments. Other datasets, which are created as an intermediate step of creating the tropospheric ozone column data, are (i) a daily 1∘×1∘ clear-sky and total ozone column from OMI and TROPOMI, (ii) a daily 1∘×1∘ homogenized and interpolated dataset of ozone profiles from limb instruments, and (iii) a daily 1∘×1∘ dataset of ozone profiles from SILAM simulations with adjustment to satellite data. These datasets can be used in various studies related to variability and trends in ozone distributions in both the troposphere and the stratosphere. The datasets are processed from the beginning of OMI and TROPOMI measurements until December 2020 and are planned to be regularly extended in the future.

During spring 2020, the COVID-19 pandemic caused massive reductions in emissions from industry and ground and airborne transportation. To explore the resulting atmospheric composition changes, we conducted the BLUESKY campaign with two research aircraft and measured trace gases, aerosols, and cloud properties from the boundary layer to the lower stratosphere. From 16 May to 9 June 2020, we performed 20 flights in the early COVID-19 lockdown phase over Europe and the Atlantic Ocean. We found up to 50% reductions in boundary layer nitrogen dioxide concentrations in urban areas from GOME-2B satellite data, along with carbon monoxide reductions in the pollution hot spots. We measured 20%-70% reductions in total reactive nitrogen, carbon monoxide, and fine mode aerosol concentration in profiles over German cities compared to a 10-yr dataset from passenger aircraft. The total aerosol mass was significantly reduced below 5 km altitude, and the organic aerosol fraction also aloft, indicative of decreased organic precursor gas emissions. The reduced aerosol optical thickness caused a perceptible shift in sky color toward the blue part of the spectrum (hence BLUESKY) and increased shortwave radiation at the surface. We find that the 80% decline in air traffic led to substantial reductions in nitrogen oxides at cruise altitudes, in contrail cover, and in resulting radiative forcing. The light extinction and depolarization by cirrus were also reduced in regions with substantially decreased air traffic. General circulation-chemistry model simulations indicate good agreement with the measurements when applying a reduced emission scenario. The comprehensive BLUESKY dataset documents the major impact of anthropogenic emissions on the atmospheric composition.

Two airborne field campaigns focusing on observations of Arctic mixed-phase clouds and boundary layer processes and their role with respect to Arctic amplification have been carried out in spring 2019 and late summer 2020 over the Fram Strait northwest of Svalbard. The latter campaign was closely connected to the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. Comprehensive datasets of the cloudy Arctic atmosphere have been collected by operating remote sensing instruments, in-situ probes, instruments for the measurement of turbulent fluxes of energy and momentum, and dropsondes on board the AWI research aircraft Polar 5. In total, 24 flights with 111 flight hours have been performed over open ocean, the marginal sea ice zone, and sea ice. The datasets follow documented methods and quality assurance and are suited for studies on Arctic mixed-phase clouds and their transformation processes, for studies with a focus on Arctic boundary layer processes, and for satellite validation applications. All datasets are freely available via the world data center PANGAEA.

Recently it became possible to acquire and adapt the most up-to-date models of local atmospheric dynamics - WRF, transport and transformation of air pollutants - CMAQ, and the emission model SMOKE. This gave the opportunity to conduct extensive studies of the atmospheric composition climate of the country on fully competitive modern level. Ensemble, sufficiently exhaustive and representative to make reliable conclusions for atmospheric composition - typical and extreme situations with their specific space and temporal variability was created by using of computer simulations. On this basis statistically significant ensemble of corresponding Air Quality indices (AQI) was calculated, and their climate - typical repeatability, space and temporal variability for the territory of the country was constructed. The Air Quality (AQ) impact on human health and quality of life is evaluated in the terms of AQI, which give an integrated assessment of the impact of pollutants and directly measuring the effects of AQ on human health. All the AQI evaluations are on the basis of air pollutant concentrations obtained from the numerical modelling and make it possible to revile the AQI status spatial/temporal distribution and behavior. The presented results, allow to follow highest recurrence of the indices for the whole period and seasonally, and to analyze the possible reason for high values in the Moderate, High and Very High bands.

Observations of the atmospheric sources and sinks of carbon dioxide (CO2) and methane (CH4) in the pan-Arctic domain are extremely scarce, limiting our knowledge of carbon turnover in this climatically sensitive environment and the fate of the enormous carbon reservoirs conserved in the permafrost. Especially critical are the gaps in the high latitudes of Siberia, covered by the vast permafrost underlain tundra, where only several atmospheric monitoring sites are operational. This paper presents the first two years (September 2018–January 2021) of accurate continuous observations of atmospheric CO2 and CH4 dry mole fractions at the recently deployed tower-based measurement station “DIAMIS” (73.5068° N, 80.5198° E) located on the southwestern coast of the Taimyr Peninsula, Siberia, at the Gulf of the Yenisei River that opens to the Kara Sea (Arctic Ocean). In this paper, we summarized the scientific rationale of the site, examined the seasonal footprint of the station with an analysis of terrestrial vegetation and maritime sector contributing to the captured atmospheric signal, and illustrated temporal patterns of CO2 and CH4 for the daytime mixed atmospheric layer over the continent–sea interface. Along with the temporal variations reflecting a signal caused pan-Arctic and not very much influenced by the local processes, we analyzed the spatiotemporal distribution of the synoptic anomalies representing the atmospheric signatures of regional sources and sinks of CO2 and CH4 for the studied high-arctic Siberian domain of ~625 thousand km2, with nearly equal capturing the land surface (54%) and the ocean (46%) throughout the year. Both for CO2 and CH4, we have observed a sea–continent declining trend, presuming a larger depletion of trace gases in the maritime air masses compared to the continental domain. So far, over the Kara Sea, we have not detected any prominent signals of CH4 that might have indicated processes of subsea permafrost degradation and occurrence of cold seeps–still mainly observed in the eastern Arctic Seas—The Laptev Sea and the East-Siberian Sea.

Aerosols influence the Earth's energy balance directly by modifying the radiation transfer and indirectly by altering the cloud microphysics. Anthropogenic aerosol emissions dropped considerably when the global COVID-19 pandemic resulted in severe restraints on mobility, production, and public life in spring 2020. We assess the effects of these reduced emissions on direct and indirect aerosol radiative forcing over Europe, excluding contributions from contrails. We simulate the atmospheric composition with the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model in a baseline (business-as-usual) and a reduced emission scenario. The model results are compared to aircraft observations from the BLUESKY aircraft campaign performed in May–June 2020 over Europe. The model agrees well with most of the observations, except for sulfur dioxide, particulate sulfate, and nitrate in the upper troposphere, likely due to a biased representation of stratospheric aerosol chemistry and missing information about volcanic eruptions. The comparison with a baseline scenario shows that the largest relative differences for tracers and aerosols are found in the upper troposphere, around the aircraft cruise altitude, due to the reduced aircraft emissions, while the largest absolute changes are present at the surface. We also find an increase in all-sky shortwave radiation of 0.21 ± 0.05 W m−2 at the surface in Europe for May 2020, solely attributable to the direct aerosol effect, which is dominated by decreased aerosol scattering of sunlight, followed by reduced aerosol absorption caused by lower concentrations of inorganic and black carbon aerosols in the troposphere. A further increase in shortwave radiation from aerosol indirect effects was found to be much smaller than its variability. Impacts on ice crystal concentrations, cloud droplet number concentrations, and effective crystal radii are found to be negligible.

The deep atmosphere of Jupiter is obscured beneath thick clouds. This causes direct observations to be difficult, and thermochemical equilibrium models fill in the observational gaps. This research uses Galileo and Juno data together with the Gibbs free energy minimization code GGCHEM to update the gas phase and condensation equilibrium chemistry of the deep atmosphere of Jupiter down to 1000 bars. Specifically, the Galileo data provides helium abundances and, with the incorporated Juno data, we use new enrichment values for oxygen, nitrogen, carbon and sulphur. The temperature profile in Jupiter’s deep atmosphere is obtained following recent interior model calculations that fit the gravitational harmonics measured by Juno. Following this approach, we produced pressure–mixing ratio plots for H, He, C, N, O, Na, Mg, Si, P, S and K that give a complete chemical model of all species occurring to abundances down to a 10−20 mixing ratio. The influence of the increased elemental abundances can be directly seen in the concentration of the dominant carriers for each element: the mixing ratio of NH3 increased by a factor of 1.55 as compared with the previous literature, N2 by 5.89, H2O by 1.78, CH4 by 2.82 and H2S by 2.69. We investigate the influence of water enrichment values observed by Juno on these models and find that no liquid water clouds form at the oxygen enrichment measured by Galileo, EH2O = 0.47, while they do form at higher water abundance as measured by Juno. We update the mixing ratios of important gas phase species, such as NH3, H2O, CO, CH4 and H2S, and find that new gas phase species, such as CN−, (NaCN)2, S2O and K+, and new condensates, namely H3PO4 (s), LiCl (s), KCl (s), NaCl (s), NaF (s), MgO (s), Fe (s) and MnS (s), form in the atmosphere. Publisher PDF

It is well-documented that the United States (US), along with other mid-latitude land locations, has experienced warming in recent decades in response to changes in atmospheric composition. Among other changes, Easterling (2002) reported that the frost-free period is now longer across much of the US with the first frost in fall occurring later and the last freeze in spring occurring earlier. In this investigation, we explore spatial and temporal variations in all freeze warnings issued by the US National Weather Service. Freeze warning counts are highest in the southeastern US peaking overall in the spring and fall months. Freeze warnings tend to occur more toward summer moving northward and westward into more northerly states. Consistent with the warming in recent decades, we find statistically significant northward movements in freeze warning centroids in some months (December, February) across the study period (2005–2018). Detection of spatial and temporal trends in freeze warnings may be of interest to any number of scientists with applied climatological interests.

We examined daily level-3 satellite retrievals of Atmospheric Infrared Sounder (AIRS) CO, Ozone Monitoring Instrument (OMI) SO2 and NO2, and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) over eastern China to understand how COVID-19 lockdowns affected atmospheric composition. Changes in 2020 were strongly dependent on the choice of background period since 2005 and whether trends in atmospheric composition were accounted for. Over central east China during the 23 January–8 April lockdown window, CO in 2020 was between 3 % and 12 % lower than average depending on the background period. The 2020 CO was not consistently less than expected from trends beginning between 2005 and 2016 and ending in 2019 but was 3 %–4 % lower than the background mean during the 2017–2019 period when CO changes had flattened. Similarly for AOD, 2020 was between 14 % and 30 % lower than averages beginning in 2005 and 14 %–17 % lower compared to different background means beginning in 2016. NO2 in 2020 was between 30 % and 43 % lower than the mean over different background periods and between 17 % and 33 % lower than what would be expected for trends beginning later than 2011. Relative to the 2016–2019 period when NO2 had flattened, 2020 was 30 %–33 % lower. Over southern China, 2020 NO2 was between 23 % and 27 % lower than different background means beginning in 2013, the beginning of a period of persistently lower NO2. CO over southern China was significantly higher in 2020 than what would be expected, which we suggest was partly because of an active fire season in neighboring countries. Over central east and southern China, 2020 SO2 was higher than expected, but this depended strongly on how daily regional values were calculated from individual retrievals and reflects background values approaching the retrieval detection limit. Future work over China, or other regions, needs to take into account the sensitivity of differences in 2020 to different background periods and trends in order to separate the effects of COVID-19 on air quality from previously occurring changes or from variability in other sources.

In the future, large wildfires are expected to become more frequent and intense. Not only do they pose a serious threat to people and ecosystems, but they also affect the Earth's atmosphere. Aerosols from large wildfires can even reach the stratosphere where they can linger for months to years. However, little is known about their impact on climate. In particular, the potential of large wildfires to cause temperature changes in the stratosphere has hardly been studied.In our study, we analyze two extreme wildfire events, those in 2017 in North America and those in 2019/20 in Australia, using new satellite observational data. We find strong effects of the fires on the atmospheric temperature structure and short-term climate in the stratosphere. The results show significant warming of the lower stratosphere by up to 10 K within the aerosol clouds emitted by the wildfires immediately after their formation. The climate signal in the lower stratosphere persists for several months, reaching 1 K for the 2017 North American wildfires and a remarkable 3.5 K for the 2019/20 Australian wildfires. This is stronger than any signal from volcanic eruptions in the past two decades. Such extreme events potentially influence the atmospheric composition and stratospheric temperature trends, underscoring their importance for future climate.Improved knowledge of the temperature signals from extreme wildfires is particularly important for trend analysis. Our ongoing research on this topic aims to further improve the separation of natural variability from anthropogenic influences in climate trend detection, especially in the stratosphere.

Atmospheric pollution has many profound effects on human health, ecosystems, and the climate. Of concern are high concentrations and deposition of reactive nitrogen (Nr) species, especially of reduced N (gaseous NH3, particulate NH4+). Atmospheric chemistry and transport models (ACTMs) are crucial to understanding sources and impacts of Nr chemistry and its potential mitigation. Here we undertake the first evaluation of the global version of the EMEP MSC-W ACTM driven by WRF meteorology (1° × 1° resolution), with a focus on surface concentrations and wet deposition of N and S species relevant to investigation of atmospheric Nr and secondary inorganic aerosol (SIA). The model-measurement comparison is conducted both spatially and temporally, covering 9 monitoring networks worldwide. Model simulations for 2010 compared use of both HTAP and ECLIPSEE (ECLIPSE annual total with EDGAR monthly profile) emissions inventories; those for 2015 used ECLIPSEE only. Simulations of primary pollutants are somewhat sensitive to the choice of inventory in places where regional differences in primary emissions between the two inventories are apparent (e.g. China), but much less so for secondary components. For example, the difference in modelled global annual mean surface NH3 concentration using the two 2010 inventories is 18 % (HTAP: 0.26 μg m−3; ECLIPSEE: 0.31 μg m−3) but only 3.5 % for NH4+ (HTAP: 0.316 μg m−3; ECLIPSEE: 0.305 μg m−3). Comparisons of 2010 and 2015 surface concentrations between model and measurement demonstrate that the model captures well the overall spatial and seasonal variations of the major inorganic pollutants NH3, NO2, SO2, HNO3, NH4+, NO3−, SO42−, and their wet deposition in East Asia, Southeast Asia, Europe and North America. The model shows better correlations with annual average measurements for networks in Southeast Asia (Mean R for 7 species:  = 0.73), Europe ( = 0.67) and North America ( = 0.63) than in East Asia ( = 0.35) (data for 2015), which suggests potential issues with the measurements in the latter network. Temporally, both model and measurement agree on higher NH3 concentrations in spring and summer, and lower concentrations in winter. The model slightly underestimates annual total precipitation measurements (by 13–34 %) but agrees well with the spatial variations in precipitation in all four world regions (0.65–0.78 R range). High correlations between measured and modelled NH4+ precipitation concentrations are also observed in all regions except East Asia. For annual total wet deposition of reduced N, the greatest consistency is in North America (R = 0.75), followed by Southeast Asia (R = 0.68) and Europe (R = 0.61). Model-measurement bias varies between species in different networks; for example, bias for NH4+ and NO3− is most in Europe and North America and least in East and Southeast Asia. The greater uniformity in spatial correlations than in biases suggests that the major driver of model-measurement discrepancies (aside from differing spatial representativeness and uncertainties and biases in measurements) are shortcomings in absolute emissions rather than in modelling the atmospheric processes. The comprehensive evaluations presented in this study support the application of this model framework for global analysis of current and potential future budgets and deposition of Nr and SIA.

Networks of long-term measurements of trace gases are critical for understanding spatio-temporal trends in air pollutants. This data is used to assess long-range and trans-boundary transport of emissions, quantify effects on public health, develop mitigation strategies and examine the impact of implemented policy changes. As part of the European Monitoring and Evaluation Programme (EMEP), the UK operates two “super sites” which have provided a suite of co-located measurements for this purpose. These supersites have been running for decades, and are located in rural background conditions, with the intention of being representative of the north and south of the country. A Monitor for AeRosols and Gases in ambient Air (MARGA; Metrohm Applikon, NL) has been included in these sites’ measurements for over a decade. However its gaseous measurements of nitric acid (HNO3) have been demonstrated to include potential artefacts from other oxidised reactive nitrogen species (NOy), such as dinitrogen pentoxide (N2O5). This interference has not yet been formally quantified. Other NOy measurements at either site are infrequent. Nitryl chloride (ClNO2) in particular was first measured in the UK in 2012, and has been measured only sporadically since. Meteorological variables are similarly measured in networks to provide locally representative data, which are utilised in atmospheric chemistry and chemical transport models. Photolysis reactions are key drivers of atmospheric chemistry, initiating many reaction routes via the production of reactive radical species. As such, accurate estimation of photolysis rate constants (or photolysis frequencies; j-values) are imperative for understanding subsequent reactions and predicting accurate pollutant concentrations. Photolysis rate constants are highly influenced by local meteorology (e.g. clouds, aerosols), but capturing the spatio-temporal variability of these changing conditions is challenging, and often computationally costly. Consequently, modelled j-values are often parameterised or determined for unrepresentative local conditions, and results are not validated beyond model conception. Some studies apply adjustment factors to these model results to account for local conditions, but these have not yet been standardised nor explored. Part of this PhD research presents a systematic analysis of a measurement-driven adjustment factor (MDAF) to adjust clear-sky or cloud-free modelled j-values to capture changes in the local meteorology. MDAFs were derived from the ratios of j-values from both filter- and spectral radiometer measurements and clear-sky estimates from the Tropospheric Ultraviolet and Visible radiative transfer model (TUV). MDAFs were examined in terms of space (3 UK sites), time resolution (hourly to annual averages), photolysis reactions (12 studied), optical inlet used (4-π sr and 2-π sr) and qualitative impact on model chemical schemes. MDAFs derived from j(NO2) were found to be seasonally similar around the UK, but specific to local environments at higher time resolutions, demonstrating the importance of local j-value measurements. Downwelling (2-π) MDAFs demonstrated a slight increase with solar zenith angle (SZA), which was amplified when measurements of upwelling j(NO2) were considered (4-π). Increased surface albedo (snow cover) resulted in approximately 36% lower downwelling compared with 4-π MDAF, but the difference was negligible at other times. Derivations of MDAF for the 12 different atmospheric photolysis reactions were grouped using hierarchical cluster analysis (HCA). The groupings of the photolysis reactions were found to be driven by the extent to which a species photodissociates at longer (UVA) wave-lengths. MDAFs derived from j(NO2) measurements were deemed an applicable reference for local adjustment of the j-values for other photodissociations at wavelengths >350 nm. For j-values of photodissociations at shorter wavelengths, adjustment using MDAFs based on a reference of j(O1D) resulted in lower total error. The presence of clouds had a greater influence on reducing cloud-free model results of j(NO2) (approx. 45%). Shorter wavelengths, such as those required for the photolysis rate constant j(O1D), are scattered more readily in clear skies, and thus resulted in a lower magnitude difference (20%). The other part of this PhD investigated atmospheric composition at the two UK supersites, by assessing the impact of the relocation of the southern EMEP supersite from Harwell to Chilbolton Observatory, and deploying an iodide chemical ionisation mass spectrometer (I – CIMS) to measure NOy species at the northern supersite (Auchencorth Moss). Meteorological normalisation was used on a concatenated time series of pollutant concentrations pre- and post-relocation from Harwell to Chilbolton Observatory, to identify any resulting effects of the move on these time series. Of all the species considered, only nitrogen oxides (NOx) and ammonia (NH3) had a step change in concentration, both increasing. The additional contributing sources at Chilbolton Observatory were identified. As a consequence, the long-term time series of NOx and NH3 should be considered to be restarted following the relocation, and the new site not strictly representative of the wider area it is intended to be. The aim of the CIMS study at Auchencorth Moss was to measure HNO3 and N2O5 to quantify the interference in co-located MARGA measurements, as well as to contribute the first Scottish ClNO2 measurements. The challenges of this study, and future work required is discussed. This PhD research has demonstrated a new potential application of meteorological normalisation for air quality site relocations, which will become more pertinent in future years where background sites will on occasion need to be relocated due to local development. Furthermore, this study has emphasised the importance of measuring local photolysis rate constants to account for highly variable local conditions. It provides discussion around making existing measurements standardised and accessible, so as to make more frequent model validation or implementation of MDAF-like metrics easier, and to improve modelled estimations of local photolysis rate constants without significantly increasing computational cost. This PhD research explores the ongoing need to measure both atmospheric chemical components and photolysis rate constants to understand changes in the atmosphere as pollutant emission abatement policies are implemented under real local conditions.

The atmospheric composition in urban areas is one of the primary tasks in air pollution studies. The research aims to provide a statistically reliable assessment of the atmospheric composition climate of the city of Sofia—typical and extreme features of the special/temporal behavior, annual means, seasonal and diurnal variations. For that purpose, extensive numerical simulations of the atmospheric composition fields in Sofia city have been performed. Three models were chosen as modeling tools. We used WRF as a meteorological pre-processor, CMAQ as a chemical transport model, and SMOKE as the emission pre-processor of Models-3 system. We developed the following conclusions. The daily concentration changes of the two essential air pollution species—nitrogen dioxide (NO2) and fine particle matters (FPRM, particulate matter (PM2.5), which has a diameter between 0 and 2.5 micrometers)—have different magnitudes. Second, the emissions relative contributions to the concentration of different species could be different, varying from 0% to above 100%. The contributions of different emission categories to other species surface concentrations have various diurnal courses. Last, the total concentration change (ΔC) is different for each pollutant. The sign of the contributions of some processes is evident. Still, some may have different signs depending on the type of emissions, weather conditions, or topography.

Australian fires are a primary driver of variability in Australian atmospheric composition and contribute significantly to regional and global carbon budgets. However, biomass burning emissions fro...