Littérature scientifique sur le sujet « Long duration stratospheric– »

Abstract. Polar stratospheric clouds play a significant role in the seasonal thinning of the ozone layer by facilitating the activation of stable chlorine and bromine reservoirs into reactive radicals, as well as prolonging the ozone depletion by removing HNO3 and H2O from the stratosphere by sedimentation. In a context of climate change, the cooling of the lower polar stratosphere could enhance polar stratospheric cloud (PSC) formation and by consequence cause more ozone depletion. There is thus a need to document the evolution of the PSC cover to better understand its impact on the ozone layer. In this article we present a statistical model based on the analysis of the CALIPSO (Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations) PSC product from 2006 to 2020. The model predicts the daily regionally averaged PSC density by pressure level derived from stratospheric temperatures. Applied to stratospheric temperatures from the CALIPSO PSC product, our model reproduces observed and interannual variations in PSC density well between 10 and 150 hPa over the 2006–2020 period. The model reproduces the PSC seasonal progression well, even during disruptive events like stratospheric sudden warmings, except for years characterized by volcanic eruptions. We also apply our model to gridded temperatures from Modern Era Retrospective analysis for Research and Application (MERRA-2) reanalyses over the complete South Pole region to evaluate changes in PSC season duration over the 1980–2021 period. We find that over the 1980–2000 period, the PSC season gets significantly longer between 30 and 150 hPa. Lengthening of the PSC season from 22 d (30–50 hPa) to 32 d (100–150 hPa) is possibly related to volcanic eruptions occurring over this period. Over 1980–2021, we find that the PSC season gets significantly longer between 30 and 100 hPa, but due to biases in MERRA-2 temperatures, the reliability of these trends is hard to evaluate.

Extreme warm stratospheric events during polar winters from ERA-Interim reanalysis and CMIP5-ESM-LR runs were separated by duration and strength of the polar-night jet oscillation (PJO) using a high statistical confidence level of three standard deviations (strong-PJO events). With a composite analysis, we demonstrate that strong-PJO events show a significantly stronger downward propagating signal in both, northern annular mode (NAM) and zonal mean zonal wind anomaly in the stratosphere in comparison with non-PJO events. The lower stratospheric EP-flux-divergence difference in ERA-Interim was stronger in comparison to long-term CMIP5-ESM-LR runs (by a factor of four). This suggests that stratosphere–troposphere coupling is stronger in ERA-Interim than in CMIP5-ESM-LR. During the 60 days following the central date (CD), the Arctic oscillation signal was more intense during strong-PJO events than during non-PJO events in ERA-Interim data in comparison to CMIP5-ESM-LR runs. During the 15-day phase after CD, strong PJO events had a significant increase in stratospheric ozone, upper tropospheric zonally asymmetric impact, and a regional surface impact in ERA-Interim. Finally, we conclude that the applied high statistical threshold gives a clearer separation of extreme warm stratospheric events into strong-PJO events and non-PJO events including their different downward propagating NAM signal and tropospheric impacts.

The stratospheric airship, as a near-space vehicle, is increasingly utilized in scientific exploration and Earth observation due to its long endurance and regional observation capabilities. However, due to the complex characteristics of the stratospheric wind field environment, trajectory planning for stratospheric airships is a significant challenge. Unlike lower atmospheric levels, the stratosphere presents a wind field characterized by significant variability in wind speed and direction, which can drastically affect the stability of the airship’s trajectory. Recent advances in deep reinforcement learning (DRL) have presented promising avenues for trajectory planning. DRL algorithms have demonstrated the ability to learn complex control strategies autonomously by interacting with the environment. In particular, the proximal policy optimization (PPO) algorithm has shown effectiveness in continuous control tasks and is well suited to the non-linear, high-dimensional problem of trajectory planning in dynamic environments. This paper proposes a trajectory planning method for stratospheric airships based on the PPO algorithm. The primary contributions of this paper include establishing a continuous action space model for stratospheric airship motion; enabling more precise control and adjustments across a broader range of actions; integrating time-varying wind field data into the reinforcement learning environment; enhancing the policy network’s adaptability and generalization to various environmental conditions; and enabling the algorithm to automatically adjust and optimize flight paths in real time using wind speed information, reducing the need for human intervention. Experimental results show that, within its wind resistance capability, the airship can achieve long-duration regional station-keeping, with a maximum station-keeping time ratio (STR) of up to 0.997.

AbstractWe report on the activities preparing long duration stratospheric flights, suitable for CMB (Cosmic Microwave Background) measurements, in the Arctic region. We focus on pathfinder flights, and on two forthcoming experiments to be flown from Longyearbyen (Svalbard islands): the OLIMPO Sunyaev-Zeldovich spectrometer, and the Large-Scale Polarization Explorer (LSPE).

Abstract. The deployment of the imaging Fourier Transform Spectrometer GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) on board a long-duration balloon for stratospheric research requires a blackbody for in-flight calibration in order to provide traceability to the International Temperature Scale (ITS-90) to ensure comparability with the results of other experiments and over time. GLORIA, which has been deployed onboard various research aircraft such as the Russian M55 Geophysica or the German HALO in the past, shall also be used for detailed atmospheric measurements in the stratosphere up to 40 km altitude. The instrument uses a two-dimensional detector array and an imaging optics with a large aperture diameter of 36 mm and an opening angle of 4.07∘ × 4.07∘ for infrared limb observations. To overfill the field of view (FOV) of the instrument, a large-area blackbody radiation sources (125 mm × 125 mm) is required for in-flight calibration. In order to meet the requirements regarding the scientific goals of the GLORIA missions, the radiance temperature of the blackbody calibration source has to be determined to better than 100 mK and the spatial temperature uniformity shall be better than 150 mK. As electrical resources on board a stratospheric balloon are very limited, the latent heat of the phase change of a eutectic material is utilized for temperature stabilization of the calibration source, such that the blackbody has a constant temperature of about −32 ∘C corresponding to a typical temperature observed in the stratosphere. The Institute for Atmospheric and Environmental Research at the University of Wuppertal designed and manufactured a prototype of the large-area blackbody for in-flight calibration of an infrared interferometer deployed on board a long-duration balloon for stratospheric research. This newly developed calibration source was tested under lab conditions as well as in a climatic and environmental test chamber in order to verify its performance especially under flight conditions. At the PTB (Physikalisch-Technische Bundesanstalt), the German national metrology institute, the spatial radiance distribution of the blackbody was determined and traceability to the International Temperature Scale (ITS-90) has been assured. In this paper the design and performance of the balloon-borne blackbody (BBB) is presented.

L’importance relative des différents mécanismes qui gouvernent l’abondance et la tendance à long terme de vapeur d’eau stratosphérique est encore mal quantifiée. La haute troposphère et la basse stratosphère tropicale (TTL) est la porte d’entrée de toute espèce vers la stratosphère. Les processus tels que le piège froid, les ondes et la convection profonde stratosphérique (overshoot) sont les processus essentiels qui modulent l’abondance de la vapeur d’eau pénétrant la stratosphère.Le projet Stratéole 2, basé sur plusieurs campagnes de ballons longue durée, peut permettre l’étude de ces processus dans toute la ceinture tropicale en apportant une large base de données inédite.Dans le cadre de cette thèse, les mesures de vapeur d’eau in situ réalisées par les 5 instruments Pico-Strat bi-gaz (GSMA/DT INSU) pendant les deux premières campagnes de Stratéole 2, sont analysées pour quantifier l’impact des ondes et de la convection profonde sur le bilan d’eau stratosphérique. Une méthode basée sur le calcul d’anomalies de vapeur d’eau (X’) est développée pour mettre en évidence ces signatures.En extrayant pour chaque vol les perturbations de températures (T’), tiré d’un diagramme de Hovmöller (longitude/temps) le long de la trajectoire du ballon, et en les corrélant aux anomalies de vapeur d’eau, on met en évidence, notamment pour le premier et le dernier vol de la campagne, le rôle majeur que jouent les ondes dans la modulation de vapeur d’eau.Pour d’autres vols, des corrélations plus faibles, voire des anti-corrélations sont obtenues. On montre, en tenant compte du gradient vertical de vapeur d’eau issu de mesures satellites, que ces anti-corrélations sont dues à des déplacements verticaux de masses d’air sous l’influence d’ondes de grande/moyenne échelle.La proportion des X’ compatibles avec un déplacement isentrope des masses d’air dû aux ondes, varie entre 48% et 70% selon les vols, confirmant le rôle majoritaire que peuvent jouer les ondes dans nos mesures.Le rôle de la convection profonde sur X’ est également étudié. Tout d’abord, en utilisant des profils verticaux obtenus lorsque les ballons ont dépressurisé au-dessus de systèmes convectifs profonds. Aucune signature systématique n’est détectée dans ces cas.Entre le 12 et le 15 décembre 2021, deux instruments Pico-STRAT Bi Gaz ont pu réaliser des mesures à proximité du cyclone Rai. Les mesures montrent des processus irréversibles et de fortes hydratations de la basse stratosphère dues à la convection profonde générée dans les bras du cyclone, ce qui est un résultat inédit par des mesures in situ au-dessus de ces systèmes.L’analyse des signatures convectives en utilisant des produits de sommet de nuage (satellites géostationnaires Himawari et GOES) et des rétro-trajectoires par le modèle HYSPLIT, montre que 33 nuits de notre jeu de données in situ voient leurs X’ compatibles avec une hydratation ou déshydratation par des overshoots. Deux cas ont été modélisés par le modèle méso-échelle méso-NH pour confirmer l’origine convective de certaines signatures remarquables. La simulation à 3 grilles imbriquées du cas du 28/01/2020 au-dessus de Sumatra corrobore l’hypothèse d’overshoots stratosphériques à l’origine d’anomalies de vapeur d’eau d’environ 0,6 ppmv.Cette étude montre la capacité de la méthode d’anomalies employée à mettre en évidence des signatures ondulatoires ou des signatures de convection profonde dans la ceinture équatoriale. On souligne l’importance des ondes sur le jeu de mesures, mais également, de quelques cas convectifs extrêmes (cyclone Rai) qu’il conviendra d’étudier en détail dans un futur proche
The relative importance of the different mechanisms governing the abundance and long-term trend of stratospheric water vapour is still poorly quantified. The upper troposphere and tropical lower stratosphere (TTL) is the gateway to the stratosphere for all species. Processes such as the cold trap, waves and deep stratospheric convection (overshoot) are the essential ones that modulate the abundance of water vapor entering the stratosphere.The Stratéole 2 project, based on several long-duration balloon campaigns, will enable us to study these processes throughout the tropical belt, by providing a large, unprecedented database.In this thesis, in situ water vapor measurements made by the 5 Pico-STRAT Bi-Gaz instruments (GSMA/DT INSU) during the first two Stratéole 2 campaigns are analyzed to quantify the impact of waves and deep convection on the stratospheric water balance. A method based on the calculation of water vapour anomalies (X') is developed to highlight these signatures.By extracting the temperature perturbations (T') for each flight, taken from a Hovmöller diagram (longitude/time) along the balloon's trajectory, and correlating them with the water vapour anomalies, we highlight, particularly for the first and last flights of the campaign, the major role played by waves in water vapour modulation.For other flights, we obtain weaker correlations, or even anti-correlations. Considering the vertical water vapour gradient derived from satellite measurements, we show that these anti-correlations are due to vertical displacements of air masses under the influence of large/medium scale waves.The proportion of X' compatible with isentropic displacement of air masses due to waves, varies between 48% and 70% depending on the flight, confirming the major role that waves can play in our measurements.The role of deep convection on X' is also investigated. Firstly, using vertical profiles obtained when balloons depressurized above deep convective systems. No systematic signature is detected in these cases.Between December 12 and 15, 2021, two Pico-STRAT Bi Gaz instruments were able to take measurements in the vicinity of cyclone Rai. The measurements show irreversible processes and strong hydration of the lower stratosphere due to deep convection generated in the cyclone’s arms which is an unprecedented result by in situ measurements over these systems.Analysis of convective signatures using cloud top products (Himawari and GOES geostationary satellites) and back-trajectories by the HYSPLIT model, shows that 33 nights in our in situ dataset have X' consistent with hydration or dehydration by overshoots. one case was modelled by the mesoscale model meso-NH to confirm the convective origin of some remarkable signatures. The 3 nested grid simulation of the case of 28/01/2020 over Sumatra supports the hypothesis of stratospheric overshoots causing water vapour anomalies of around 0,6 ppmv.This study demonstrates the ability of the anomaly method employed to highlight wave signatures or signatures of deep convection in the equatorial belt. It highlights the importance of waves in the set of measurements, as well as some extreme convective cases (cyclone Rai), which will need to be studied in detail in the near future

We built a collector to filter interplanetary dust particles (IDPs) larger than 5 µm from the clean air at the Amundsen Scott South Pole station. Our sampling strategy used long duration, continuous dry filtering of near-surface air in place of short duration, high-speed impact collection on flags flown in the stratosphere. We filtered ~107 m³ of clean Antarctic air through 20 cm diameter, 3 µm filters coupled to a suction blower of modest power consumption (5–6 kW). Our collector ran continuously for 2 years and yielded 41 filters for analyses. Based on stratospheric concentrations, we predicted that each month’s collection would provide 300–900 IDPs for analysis. We identified 19 extraterrestrial (ET) particles on the 66 cm² of filter examined, which represented ~0.5% of the exposed filter surfaces. The 11 ET particles larger than 5 µm yield about a fifth of the expected flux based on >5 µm stratospheric ET particle flux. Of the 19 ET particles identified, four were chondritic porous IDPs, seven were FeNiS beads, two were FeNi grains, and six were chondritic material with FeNiS components. Most were <10 µm in diameter and none were cluster particles. Additionally, a carbon-rich candidate particle was found to have a small ¹⁵N isotopic enrichment, supporting an ET origin. Many other candidate grains, including chondritic glasses and C-rich particles with Mg and Si and FeS grains, require further analysis to determine if they are ET. The vast majority of exposed filter surfaces remain to be examined.