Evaluating stratospheric ozone and water vapour changes in CMIP6 models from 1850 to 2100

Stratospheric ozone and water vapour are key components of the Earth system, and past and future changes to both have important impacts on global and regional climate. Here, we evaluate long-term changes in these species from the pre-industrial period (1850) to the end of the 21st century in Coupled Model Intercomparison Project phase 6 (CMIP6) models under a range of future emissions scenarios. There is good agreement between the CMIP multi-model mean and observations for total column ozone (TCO), although there is substantial variation between the individual CMIP6 models. For the CMIP6 multi-model mean, global mean TCO has increased from ∼300 DU in 1850 to ∼ 305 DU in 1960, before rapidly declining in the 1970s and 1980s following the use and emission of halogenated ozone-depleting substances (ODSs). TCO is projected to return to 1960s values by the middle of the 21st century under the SSP2-4.5, SSP3-7.0, SSP4-3.4, SSP4-6.0, and SSP5-8.5 scenarios, and under the SSP3-7.0 and SSP5-8.5 scenarios TCO values are projected to be ∼ 10 DU higher than the 1960s values by 2100. However, under the SSP1-1.9 and SSP1-1.6 scenarios, TCO is not projected to return to the 1960s values despite reductions in halogenated ODSs due to decreases in tropospheric ozone mixing ratios. This global pattern is similar to regional patterns, except in the tropics where TCO under most scenarios is not projected to return to 1960s values, either through reductions in tropospheric ozone under SSP1-1.9 and SSP1-2.6, or through reductions in lower stratospheric ozone resulting from an acceleration of the Brewer-Dobson circulation under other Shared Socioeconomic Pathways (SSPs). In contrast to TCO, there is poorer agreement between the CMIP6 multi-model mean and observed lower stratospheric water vapour mixing ratios, with the CMIP6 multi-model mean underestimating observed water vapour mixing ratios by ∼ 0.5 ppmv at 70 hPa. CMIP6 multi-model mean stratospheric water vapour mixing ratios in the tropical lower stratosphere have increased by ∼ 0.5 ppmv from the pre-industrial to the present-day period and are projected to increase further by the end of the 21st century. The largest increases (∼ 2 ppmv) are simulated under the future scenarios with the highest assumed forcing pathway (e.g. SSP5-8.5). Tropical lower stratospheric water vapour, and to a lesser extent TCO, shows large variations following explosive volcanic eruptions. © Author(s) 2021

Recent Trends in Monitoring of European Water Framework Directive Priority Substances Using Micro-Sensors: A 2007–2009 Review

This review discusses from a critical perspective the development of new sensors for the measurement of priority pollutants targeted in the E.U. Water Framework Directive. Significant advances are reported in the paper and their advantages and limitations are also discussed. Future perspectives in this area are also pointed out in the conclusions. This review covers publications appeared since December 2006 (the publication date of the Swift report). Among priority substances, sensors for monitoring the four WFD metals represent 81% of published papers. None of analyzed publications present a micro-sensor totally validated in laboratory, ready for tests under real conditions in the field. The researches are mainly focused on the sensing part of the micro-sensors. Nevertheless, the main factor limiting micro-sensor applications in the environment is the ruggedness of the receptor towards environmental conditions. This point constitutes the first technological obstacle to be overcome for any long-term field tests

Méthodologie de mesure du diamètre solaire par imagerie directe dans l'espace (application au traitement des données du Michelson Doppler Imager de la mission SOHO)

La variabilité du rayon solaire a longtemps été une question ouverte, intéressant à la fois les climatologues, qui voyaient en elle un possible traceur absolu d activité solaire, et les physiciens solaires, pour qui elle aurait été la manifestation de changements profonds de la structure solaire, liés au cycle de Schwabe de onze ans. Alors que les résultats des instruments au sol sont encore contradictoires, ceux des instruments spatiaux (principalement le Michelson Doppler Imager, embarqué sur le satellite SOHO) indiquent cependant une variation bien plus faible qu escomptée, ce que confirment les résultats de ce document. Le traitement du problème nécessite la prise en compte des effets instrumentaux. À cet effet, un formalisme général est introduit dans ce document, avec une modélisation générique des effets (distorsion, fonction d étalement, flat-field, bruits de mesure) et dispositifs (filtrage spectral, obturateurs) les plus courants. Une procédure de traitement a été programmée en langage MATLAB ; sa stabilité a été démontrée sur plusieurs milliers d images du MDI. Les résultats sont corrigés de la dérive, principalement instrumentale, mesurée pendant le maximum solaire ; ils montrent une dérive de rayon solaire n excédant pas 9 mas pendant la période 2002-2003 qui correspond à une décroissance du cycle compatible avec une constance compte tenu des erreurs de mesure. La routine est d une rapidité suffisante pour le traitement en flux tendu de données d origine spatiale à grande cadence ainsi que la mesure des oscillations de rayon solaire ; elle se prête à l utilisation de toute information plus précise sur la fonction d instrument (modèle de distorsion notamment). Des outils numériques visant à mesurer distorsion et fonction d étalement au limbe à partir des données elles-mêmes sont proposés et mériteraient une application au MDI afin d examiner l évolution de la figure solaire au cours du cycle de SchwabeThe question of the solar radius variation was a longstanding issue. Such a variation is not only of interest for the climatologists, who need an absolute solar activity tracer, but also for the solar physicists, who are searching for an evidence of deep structural changes of the solar interior linked to the eleven years Schwabe activity cycle. While results from ground-based instruments are still controversial, those from space instruments (mainly the Michelson Doppler Imager onboard SOHO) exhibit a much lower variation than expected, as confirmed by the results presented in this document. Algorithms taking into account instrumental effects are required for this solar radius measurement problem. A general frame is presented in this document, as well as generic models of the more usual effects (distortion, point spread function and flat-field) and instrumental devices (spectral filtering, shutters). A full treatment procedure has been programmed using MATLAB language; its numerical stability has been demonstrated on thousands of MDI images. The main instrumental trend measured during the solar maximum is used to correct the results; they show solar radius residuals lower than 9 mas during the 2002-2003 period, where the cycle is in decreasing phase, which are consistent with a constant solar radius, within the achievable precision. The computational speed of this routine is enough to treat in real time high-rate space data and to measure solar radius oscillations and is designed to take advantage of more accurate information about the instrumental function (in particular a better distortion model). Numerical tools dedicated to the measurement of distortion and PSF at the limb from the data themselves are proposed; it would be of interest to apply them to the MDI images and so making possible a monitoring of the solar figure evolution during the Schwabe cycle.VERSAILLES-BU Sciences et IUT (786462101) / SudocMEUDON-Observatoire (920482302) / SudocSudocFranceF

Assimilation of stratospheric ozone GOMOS data with the isentropic transport model MIMOSA: Comparison between sub-optimal Kalman filter and kriging

1P-6GOMOS (Global Ozone Monitoring by Occultation of Stars) is the first space instrument dedicated to the study of the atmospheric composition by the technique of stellar occultations. The experiment aboard ENVISAT satellite was designed in order to evaluate stratospheric ozone concentration and trend (and other atmospheric minor constituents) over the Earth during the last few years. Ozone concentration is variable in space and time. Spatial variability may be observed by a sufficient number of occultations and time variability by recording time series. GOMOS measurements are randomly distributed in space and time. A continuous field at grid points evenly spaced is needed to obtain a good estimate of ozone trend, climatology and variability. It allows also to interpolate satellite data at the location of ground-based NDACC measurements for validation. We present here a comparison between a heavy method consisting in the assimilation of GOMOS data in the high resolution isentropic transport model MIMOSA using a sub-optimal Kalman filter with a simple and fast multidimensional interpolation method: kriging

Non-orographic gravity waves: representation in climate models and effects on infrasound

International audienceLong-range infrasound propagation is controlled by atmospheric waveguides that extend up to the mesosphere and lower thermosphere and whose efficiency is affected by gravity waves (GWs). These GWs are not explicitely represented in the global models often used to calculate infrasound propagation because their spatial scales are well below the models resolution. These unresolved GWs also transport momentum and control in good part the large-scale circulation in the middle atmosphere. These two issues make that the GWs need to be parameterized to improve the datasets used to calculate infrasound propagation as well as in the Atmospheric General Circulation Models (AGCMs) that are used to make weather forecasts and climate predictions. These two issues gain in being treated in conjonction. From this, improved infrasound calculations could be made by using a realistic amount of GWs. In return, using infrasound records could help specifying important characteristics of the GWs that are parameterized in the climate models. The paper presents a research framework developed to address these issues. It first presents a non-orographic GWs parameterization used and tested in a well-established AGCM, emphasizing the most recent developments, like the introduction of stochastic techniques and a better specification of the GWs sources. The significance of GWs on the global climate is then illustrated by making sensitivity tests where the frontal and convective GWs parameters are moderatly changed. These changes impact the structure of the jets in the midlatitude stratosphere and the intensity of the sudden stratospheric warmings. The paper also presents a method to calculate long-range infrasound propagation, and to incorporate the contribution of the GWs that are parameterized in the AGCM. We then show that the changes in GW parameters tested in the model also impact infrasound propagation. This makes infrasound detection a potential tool to tune GWs parameterization in large-scale models

Analysis of the Active Material Microstructure Constituting the Positive Electrode in Lithium-Ion Batteries Application

Our project aims to complete an experimental study supported by computer modeling to bring a better understanding of the impact of the microstructure on electrochemical behavior. Research has shown in particular that the material microstructure is of tremendous importance to fully exploit its electrochemical capabilities. Indeed, a same chemical and crystallographic phase can exhibit vastly different energy densities, power capabilities and capacity retention depending on its microstructure. LiNi1/3Mn1/3Co1/3O2materials (NMC) consisting of different microstructure are used as a model compounds. NMC synthesis is set up via co-precipitation route which allows the adjustment of different synthesis parameters such as the pH, concentrations of reactants and feeding and stirring rates, to obtain different morphologies. It gives the possibility to tune the primary particle crystallinity and morphology from thin nanosized pellets to large micrometric cuboids. The differences in the resulting electrochemical performances are discussed regarding the diffusion of lithium in both solid and liquid phases, the wettability and the electronic conductivity of the material by By coupling electroanalytical techniques, microscopy and computer simulations, we show that the microstructure induces a fundamental difference in the rate-limiting step of the electrochemical process. The microstructure is first qualitatively and quantitatively investigated using mercury porosimetry, helium pycnometry helium pycnometry and FIB-SEM reconstruction. Cyclic voltammetry shows that porous materials behaviour is indeed limited by charge-transfer over a wide range of scan rates whereas dense materials are rapidly limited by solid-state diffusion. The support of modelling allows us to quantify important kinetics parameters such as diffusion coefficients, diffusion length and exchange surface areas and currents. The electronic conductivity investigated using broadband dielectric spectroscopy. This technique allows to separate and treat individually the different relaxations arising from the different length scales: crystallite, nanostructure, and microstructure. It is shown that the electronic conductivity is highly dependent on the microstructure of the primary particles. Flake-shape particles exhibit a higher conductivity, which has an effect at all larger scales. This study shows that the application of electroanalytical techniques must take into account carefully the microstructure of the studied materials and need the support of modelling to fully understand the electrochemical process. Figure 1 <jats:p /

Deoxygenation of Nitrosobenzene by the Electrogenerated Pd3(dppm)3(μ3-CO) Cluster

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