Prediction of source contributions to urban background PM10 concentrations in European cities: a case study for an episode in December 2016 using EMEP/MSC-W rv4.15 and LOTOS-EUROS v2.0 – Part 1: The country contributions

A large fraction of the urban population in Europe is exposed to particulate matter levels above the WHO guideline value. To make more effective mitigation strategies, it is important to understand the influence on particulate matter (PM) from pollutants emitted in different European nations. In this study, we evaluate a country source contribution forecasting system aimed at assessing the domestic and transboundary contributions to PM in major European cities for an episode in December 2016. The system is composed of two models (EMEP/MSC-W rv4.15 and LOTOS-EUROS v2.0), which allows the consideration of differences in the source attribution. We also compared the PM10 concentrations, and both models present satisfactory agreement in the 4 d forecasts of the surface concentrations, since the hourly concentrations can be highly correlated with in situ observations. The correlation coefficients reach values of up to 0.58 for LOTOS-EUROS and 0.50 for EMEP for the urban stations; the values are 0.58 for LOTOS-EUROS and 0.72 for EMEP for the rural stations. However, the models underpredict the highest hourly concentrations measured by the urban stations (mean underestimation of 36 %), which is to be expected given the relatively coarse model resolution used (0.25∘ longitude × 0.125∘ latitude). For the source attribution calculations, LOTOS-EUROS uses a labelling technique, while the EMEP/MSC-W model uses a scenario having reduced anthropogenic emissions, and then it is compared to a reference run where no changes are applied. Different percentages (5 %, 15 %, and 50 %) for the reduced emissions in the EMEP/MSC-W model were used to test the robustness of the methodology. The impact of the different ways to define the urban area for the studied cities was also investigated (i.e. one model grid cell, nine grid cells, and grid cells covering the definition given by the Global Administrative Areas – GADM). We found that the combination of a 15 % emission reduction and a larger domain (nine grid cells or GADM) helps to preserve the linearity between emission and concentrations changes. The nonlinearity, related to the emission reduction scenario used, is suggested by the nature of the mismatch between the total concentration and the sum of the concentrations from different calculated sources. Even limited, this nonlinearity is observed in the NO-3, NH+4, and H2O concentrations, which is related to gas–aerosol partitioning of the species. The use of a 15 % emission reduction and of a larger city domain also causes better agreement on the determination of the main country contributors between both country source calculations. Over the 34 European cities investigated, PM10 was dominated by domestic emissions for the studied episode (1–9 December 2016). The two models generally agree on the dominant external country contributor (68 % on an hourly basis) to PM10 concentrations. Overall, 75 % of the hourly predicted PM10 concentrations of both models have the same top five main country contributors. Better agreement on the dominant country contributor for primary (emitted) species (70 % is found for primary organic matter (POM) and 80 % for elemental carbon – EC) than for the inorganic secondary component of the aerosol (50 %), which is predictable due to the conceptual differences in the source attribution used by both models. The country contribution calculated by the scenario approach depends on the chemical regime, which largely impacts the secondary components, unlike the calculation using the labelling approach

Instrumentation d’une Fusée à Eau

Dans le cadre de la formation ISAE-ENSICA, un projet pédagogique autour du concept de fusée à eau a été développé. Cette fusée à eau est en fait instrumentée pour permettre l’analyse des différents paramètres de vol : accélération, vitesse et altitude en fonction du temps. Ce projet, d’un volume de 15 heures semi-encadrées, s’adresse à des étudiants d’un niveau Licence ou première année Master. En complément de la validation des notions d’électronique analogique, il permet par la même occasion d’aborder d’un point de vue pratique les principes théoriques d’aérodynamique et de mécanique du vol pour les lanceurs spatiaux. Outre l’aspect ludique évident, ce projet fait clairement apparaître les liens entre les différentes disciplines scientifiques qui constituent l’enseignement pluridisciplinaire de la formation ISAE-ENSICA

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Validation of IASI CO using in-situ data and O3 evolution in polluted plumes from Lagrangian analyses

International audienc

Caractérisation de la pollution dans la troposphère arctique : utilisation des données satellitaires et aéroportées dans le cadre de la campagne API/POLARCAT

The Arctic is a region which despite the remoteness and lack of emission sources of pollutants, is one of the most affected by the long-range transport of pollution, which can affect background pollution levels and which influence climate change both regionally and globally. Despite improvements in observing systems and numerical models in recent decades, it remains difficult to reproduce the observed pollution episodes in the Arctic especially in summertime. One possible explanation is the underestimation of modelled ozone (O3) production in forest fires plumes. Carbon monoxide (CO) is often used as a tracer of pollution transport due to its relatively long lifetime of several weeks in the troposphere. It is a reactive gas, mainly produced by the combustion of fossil fuels and vegetation burning. Moreover, since its main sink is reaction with OH radical, CO has an important role in the oxidizing power of the atmosphere it also plays an important role in the assessment of tropospheric ozone. The purpose of my thesis has been to contribute to a better understanding of transport and of the chemical mechanisms of pollutants formation in the Arctic troposphere. A combination of the new CO measurements from the IASI satellite instrument, launched in October 2006 aboard the MetOp-A and aircraft data collected during the POLARCAT campaigns of the International Polar Year (IPY), in spring and summer 2008 were used. IASI CO observations were first validated by comparison with in situ airborne measurements showing its ability to detect the evolution of high CO signatures plume as close to sources regions. The second part of the thesis used assimilation of daily IASI CO measurements (Kalman filter) in the LMDz-INCA global model to improve our understanding about sources of pollution impacting the Arctic troposphere and their transport pathways. The assimilation has improved the modelling of CO pollution episodes in the Arctic free troposphere. Model results were also evaluated using POLARCAT observations and used to examine the sensitivity of Arctic pollutant concentrations (namely the overestimation of O3 distribution and the underestimation of PAN distribution) to emissions from different regions and in particular the boreal forest fire emissions.L'Arctique est une région qui malgré l'absence et l'éloignement de sources d'émission de polluants, est l'une des plus touchées par le transport à longue échelle de la pollution, qui peut affecter les niveaux de fond de pollution et qui influence le changement climatique à l'échelle régionale et mondiale. Malgré l'amélioration des systèmes d'observations et des modèles numériques durant ces dernières décennies, il reste encore difficile de reproduire les épisodes de pollution observés en Arctique notamment en été. Une explication possible est la sous-estimation de la production d'ozone (O3) modélisée dans les panaches des feux de forêt. Le monoxyde de carbone (CO) est utilisé comme un traceur du transport de la pollution du fait de sa longue durée de vie (plusieurs semaines) dans la troposphère. Ce gaz est produit par la combustion des énergies fossiles et des feux de biomasse. De plus, étant régulé par sa réaction avec le radical OH, il joue aussi un rôle important dans le bilan de l'O3 troposphérique. Le but de mes travaux de thèse a donc été de contribuer à une meilleure compréhension du transport et des mécanismes chimiques de formation des polluants secondaires dans la troposphère arctique. Pour cela j'ai utilisé en parallèle les nouvelles mesures de CO de l'instrument satellitaire IASI qui a été lancé en octobre 2006 à bord du satellite MetOp-A et les données récoltées par des avions instrumentés lors des campagnes POLARCAT de l'Année Polaire Internationale (API), au printemps et en été 2008. Les observations CO IASI ont tout d'abord été validées en les comparant avec les mesures aéroportées in situ montrant leurs capacités à observer des panaches de signatures élevées en CO comme près des régions sources. Le deuxième volet de la thèse illustre l'apport de l'assimilation (filtre de Kalman) des mesures quotidiennes de CO IASI dans le modèle global LMDz-INCA dans l'amélioration de notre compréhension sur les émissions et des chemins de transport des polluants influençant sur la troposphère arctique. L'assimilation a ainsi permis d'améliorer la modélisation des épisodes de pollution en CO dans la troposphère libre arctique. Enfin les résultats du modèle ont également été évalués en utilisant les observations POLARCAT et utilisés pour examiner la sensibilité des concentrations de polluants en Arctique (à savoir une surestimation de la distribution de l'O3 et une sous-estimation de celle du PAN) provenant des différentes régions et en particulier des feux de forêt boréale

Caractérisation de la pollution dans la troposphère arctique (utilisation des données satellitaires et aéroportées dans le cadre de la campagne API/POLARCAT)

L Arctique est une région qui malgré l'absence et l'éloignement de sources d'émission de polluants, est l'une des plus touchées par le transport à longue échelle de la pollution, qui peut affecter les niveaux de fond de pollution et qui influence le changement climatique à l'échelle régionale et mondiale. Malgré l'amélioration des systèmes d'observations et des modèles numériques durant ces dernières décennies, il reste encore difficile de reproduire les épisodes de pollution observés en Arctique notamment en été. Une explication possible est la sous-estimation de la production d'ozone (O3) modélisée dans les panaches des feux de forêt. Le monoxyde de carbone (CO) est utilisé comme un traceur du transport de la pollution du fait de sa longue durée de vie (plusieurs semaines) dans la troposphère. C est un gaz toxique produit par la combustion des énergies fossiles et des feux de biomasse. De plus, étant régulé par sa réaction avec le radical OH, il joue aussi un rôle important dans le bilan de l'O3 troposphérique. Le but de mes travaux de thèse a donc été de contribuer à une meilleure compréhension du transport et des mécanismes chimiques de formation des polluants secondaires dans la troposphère arctique. Pour cela j'ai utilisé en parallèle les nouvelles mesures de CO de l'instrument satellitaire IASI qui a été lancé en octobre 2006 à bord du satellite MetOp-A et les données récoltées par des avions instrumentés lors des campagnes POLARCAT de l'Année Polaire Internationale (API), au printemps et en été 2008. Les observations CO IASI ont tout d'abord été validées en les comparant avec les mesures aéroportées in situ montrant leurs capacités à observer des panaches de signatures élevées en CO comme près des régions sources. Le deuxième volet de la thèse illustre l'apport de l'assimilation (filtre de Kalman) des mesures quotidiennes de CO IASI dans le modèle global LMDz-INCA dans l'amélioration de notre compréhension sur les émissions et des chemins de transport des polluants impactant sur la troposphère arctique. L assimilation a ainsi permis d améliorer la modélisation des épisodes de pollution en CO dans la troposphère libre arctique. Enfin les résultats du modèle ont également été évalués en utilisant les observations POLARCAT et utilisés pour examiner la sensibilité des concentrations de polluants en Arctique (à savoir une surestimation de la distribution de l O3 et une sous-estimation de celle du PAN) provenant des différentes régions et en particulier des feux de forêt boréale.The Arctic is a region which despite the remoteness and lack of emission sources of pollutants, is one of the most affected by the long-range transport of pollution, which can affect background pollution levels and which influence climate change both regionally and globally. Despite improvements in observing systems and numerical models in recent decades, it remains difficult to reproduce the observed pollution episodes in the Arctic especially in summertime. One possible explanation is the underestimation of modelled ozone (O3) production in forest fires plumes. Carbon monoxide (CO) is often used as a tracer of pollution transport due to its relatively long lifetime of several weeks in the troposphere. It is a reactive gas, mainly produced by the combustion of fossil fuels and vegetation burning. Moreover, since its main sink is reaction with OH radical, CO has an important role in the oxidizing power of the atmosphere it also plays an important role in the assessment of tropospheric ozone. The purpose of my thesis has been to contribute to a better understanding of transport and of the chemical mechanisms of pollutants formation in the Arctic troposphere. A combination of the new CO measurements from the IASI satellite instrument, launched in October 2006 aboard the MetOp-A and aircraft data collected during the POLARCAT campaigns of the International Polar Year (IPY), in spring and summer 2008 were used. IASI CO observations were first validated by comparison with in situ airborne measurements showing its ability to detect the evolution of high CO signatures plume as close to sources regions. The second part of the thesis used assimilation of daily IASI CO measurements (Kalman filter) in the LMDz-INCA global model to improve our understanding about sources of pollution impacting the Arctic troposphere and their transport pathways. The assimilation has improved the modelling of CO pollution episodes in the Arctic free troposphere. Model results were also evaluated using POLARCAT observations and used to examine the sensitivity of Arctic pollutant concentrations (namely the overestimation of O3 distribution and the underestimation of PAN distribution) to emissions from different regions and in particular the boreal forest fire emissions.PARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceF

Observation of CO from space over megacities

Increases of the global population combined with the economic growth in many of the developing countries are leading to an increase of urban surface area and thus globally the associated air quality issue. Human activities emit vast quantities of pollutants with carbon monoxide (CO) a prime example. Several nadir-viewing thermal infrared sounders monitor this gas from space but their limited sensitivity to the boundary layer is a well-known disadvantage of this technique. Our study investigates the performance of a new retrieval algorithm applied to Measurements of Pollution in the Troposphere (MOPITT) data (version 5) that combines the thermal infrared (TIR) with near-infrared (NIR) bands that are more sensitive to the boundary layer. This new data product is compared with the TIR-only product as well as measurements from the Infrared Atmospheric Sounding Interferometer (IASI), also a TIR sensor. The study focuses on eight megacities: Moscow, Paris, Mexico, Tehran, Baghdad, Los Angeles, Sao Paulo and Delhi. High-resolution maps of the CO distribution over these locations have been generated using a new pixel averaging technique that clearly demonstrates a CO hit-spot. Combining the satellite data with wind data from meteorological reanalysis a clear dependence of the CO distribution with near-surface wind speed direction is found. A clear reduction of CO emission over all sites between 2000-2005 and 2006-2011 is observed, reaching ~ 13% over Mexico and a megacity as Baghdad emitted the same amount of CO between 2006 and 2011 than Tehran or Mexico between 2000 and 2005

Determination of enhancement ratios of HCOOH relative to CO in biomass burning plumes by the Infrared Atmospheric Sounding Interferometer (IASI)

International audienceFormic acid (HCOOH) concentrations are often underestimated by models and its chemistry is highly uncertain. HCOOH is, however, among the most abundant atmospheric volatile organic compounds and it is potentially responsible for rain acidity in remote areas. HCOOH data from the Infrared Atmospheric Sounding Interferometer (IASI) are analyzed from 2008 to 2014, to estimate enhancement ratios from biomass burning emissions over seven regions. Fire-affected HCOOH and CO total columns are defined by combining total columns from IASI, geographic location of the fires from MODerate resolution Imaging Spectroradiometer (MODIS) and the surface wind speed field from the European Centre for Medium-Range Weather Forecasts (ECMWF). Robust correlations are found between these fire-affected HCOOH and CO total columns over the selected biomass burning regions, allowing the calculation of enhancement ratios equal to 7.30 × 10−3 ± 0.08 × 10−3 mol/mol over Amazonia, 11.10 × 10−3 ± 1.37 × 10−3 mol/mol over Australia, 6.80 × 10−3 ± 0.44 × 10−3 mol/mol over India, 5.80 × 10−3 ± 0.15 × 10−3 mol/mol over Southern East Asia, 4.00 × 10−3 ± 0.19 × 10−3 mol/mol over Northern Africa, 5.00 × 10−3 ± 0.13 × 10−3 mol/mol over Southern Africa, and 4.40 × 10−3 ± 0.09 × 10−3 mol/mol over Siberia, in a fair agreement with previous studies. The comparison with other studies highlights a possible underestimation by 60 % of emission or a secondary production of HCOOH by Siberian forest fires while the studied fire plumes originating from Southern African savanna could suggest a limited secondary production of HCOOH or a limited sink. In comparison with data set characterizing emissions, it is also shown that the selected agricultural burning plumes captured by IASI over India and Southern East Asia correspond to recent plumes where the chemistry or the sink do not occur

Relative changes in CO emissions over megacities based on observations from space

International audienceUrban areas are large sources of several air pollutants with carbon monoxide (CO) among the largest. Yet measurement from space of their CO emissions remains elusive due to its long lifetime. Here we introduce a new method of estimating relative changes in CO emissions over megacities. A new multi-channel Measurements of Pollution in the Troposphere (MOPITT) CO data product, offering improved sensitivity to the boundary later, is used, to estimate this relative change over eight megacities: Moscow, Paris, Mexico, Tehran, Baghdad, Los Angeles, Sao Paulo and Delhi. By combining MOPITT observations with wind information from a meteorological reanalysis, changes in the CO upwind-downwind difference are used as a proxy for changes in emissions. Most locations show a clear reduction of CO emission between 2000-2003 and 2004-2008, reaching -43% over Tehran and -47% over Baghdad. There is contrasted agreement between these results and the MACcity and EDGARv4.2 inventories