237 research outputs found
Comparison of lidar-derived PM10 with regional modeling and ground-based observations in the frame of MEGAPOLI experiment
International audienceAn innovative approach using mobile lidar measurements was implemented to test the performances of chemistry-transport models in simulating mass concentrations (PM10) predicted by chemistry-transport models. A ground-based mobile lidar (GBML) was deployed around Paris onboard a van during the MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) summer experiment in July 2009. The measurements performed with this Rayleigh-Mie lidar are converted into PM10 profiles using optical-to-mass relationships previously established from in situ measurements performed around Paris for urban and peri-urban aerosols. The method is described here and applied to the 10 measurements days (MD). MD of 1, 15, 16 and 26 July 2009, corresponding to different levels of pollution and atmospheric conditions, are analyzed here in more details. Lidar-derived PM10 are compared with results of simulations from POLYPHEMUS and CHIMERE chemistry-transport models (CTM) and with ground-based observations from the AIRPARIF network. GBML-derived and AIRPARIF in situ measurements have been found to be in good agreement with a mean Root Mean Square Error RMSE (and a Mean Absolute Percentage Error MAPE) of 7.2 ÎŒg mâ3 (26.0%) and 8.8 ÎŒg mâ3 (25.2%) with relationships assuming peri-urban and urban-type particles, respectively. The comparisons between CTMs and lidar at ~200 m height have shown that CTMs tend to underestimate wet PM10 concentrations as revealed by the mean wet PM10 observed during the 10 MD of 22.4, 20.0 and 17.5 ÎŒg mâ3 for lidar with peri-urban relationship, and POLYPHEMUS and CHIMERE models, respectively. This leads to a RMSE (and a MAPE) of 6.4 ÎŒg mâ3 (29.6%) and 6.4 ÎŒg mâ3 (27.6%) when considering POLYPHEMUS and CHIMERE CTMs, respectively. Wet integrated PM10 computed (between the ground and 1 km above the ground level) from lidar, POLYPHEMUS and CHIMERE results have been compared and have shown similar results with a RMSE (and MAPE) of 6.3 mg mâ2 (30.1%) and 5.2 mg mâ2 (22.3%) with POLYPHEMUS and CHIMERE when comparing with lidar-derived PM10 with periurban relationship. The values are of the same order of magnitude than other comparisons realized in previous studies. The discrepancies observed between models and measured PM10 can be explained by difficulties to accurately model the background conditions, the positions and strengths of the plume, the vertical turbulent diffusion (as well as the limited vertical model resolutions) and chemical processes as the formation of secondary aerosols. The major advantage of using vertically resolved lidar observations in addition to surface concentrations is to overcome the problem of limited spatial representativity of surface measurements. Even for the case of a well-mixed boundary layer, vertical mixing is not complete, especially in the surface layer and near source regions. Also a bad estimation of the mixing layer height would introduce errors in simulated surface concentrations, which can be detected using lidar measurements. In addition, horizontal spatial representativity is larger for altitude integrated measurements than for surface measurements, because horizontal inhomogeneities occurring near surface sources are dampened
Radiative heating rates profiles associated with a springtime case of Bodélé and Sudan dust transport over West Africa
International audienceThe radiative heating rate due to mineral dust over West Africa is investigated using the radiative code STREAMER, as well as remote sensing and in situ observations gathered during the African Monsoon Multidisciplinary Analysis Special Observing Period (AMMA SOP). We focus on two days (13 and 14 June 2006) of an intense and long lasting episode of dust being lifted in remote sources in Chad and Sudan and transported across West Africa in the African easterly jet region, during which airborne operations were conducted at the regional scale, from the southern fringes of the Sahara to the Gulf of Guinea. Profiles of heating rates are computed from airborne LEANDRE 2 (Lidar EmbarquĂ© pour l'Ă©tude de l'AtmosphĂšre: Nuages Dynamique, Rayonnement et cycle de l'Eau) and space-borne CALIOP (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) lidar observations using two mineral dust model constrained by airborne in situ data and ground-based sunphotometer obtained during the campaign. Complementary spaceborne observations (from the Moderate-resolution Imaging Spectroradiometer-MODIS) and in-situ observations such as dropsondes are also used to take into account the infrared contribution of the water vapour. We investigate the variability of the heating rate on the vertical within a dust plume, as well as the contribution of both shortwave and longwave radiation to the heating rate and the radiative heating rate profiles of dust during daytime and nighttime. The sensitivity of the so-derived heating rate is also analyzed for some key variables for which the associated uncertainties may be large. During daytime, the warming associated with the presence of dust was found to be between 1.5 K dayâ1 and 4 K dayâ1, on average, depending on altitude and latitude. Strong warming (i.e. heating rates as high as 8 K dayâ1) was also observed locally in some limited part of the dust plumes. The uncertainty on the heating rate retrievals in the optically thickest part of the dust plume was estimated to be between 0.5 and 1.4 K dayâ1. During nighttime much smaller values of heating/cooling are retrieved (less than ±1 K dayâ1). Furthermore, cooling is observed as the result of the longwave forcing in the dust layer, while warming is observed below the dust layer, in the monsoon layer
Simultaneous observations of lower tropospheric continental aerosols with a ground-based, an airborne, and the spaceborne CALIOP lidar system
International audienceWe present an original experiment with multiple lidar systems operated simultaneously to study the capability of the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP), on board the Cloud-Aerosol Lidar Pathfinder Satellite Observation (CALIPSO), to infer aerosol optical properties in the lower troposphere over a midlatitude continental site where the aerosol load is low to moderate. The experiment took place from 20 June to 10 July 2007 in southern France. The results are based on three case studies with measurements coincident to CALIOP observations: the first case study illustrates a large-scale pollution event with an aerosol optical thickness at 532 nm (Ïa532) of âŒ0.25, and the two other case studies are devoted to background conditions due to aerosol scavenging by storms with Ïa532 <0.1. Our experimental approach involved ground-based and airborne lidar systems as well as Sun photometer measurements when the conditions of observation were favorable. Passive spaceborne instruments, namely the Spinning Enhanced Visible and Infrared Imager (SEVERI) and the Moderate-resolution Imaging Spectroradiometer (MODIS), are used to characterize the large-scale aerosol conditions. We show that complex topographical structures increase the complexity of the aerosol analysis in the planetary boundary layer by CALIOP when Ïa532 is lower than 0.1 because the number of available representative profiles is low to build a mean CALIOP profile with a good signal-to-noise ratio. In a comparison, the aerosol optical properties inferred from CALIOP and those deduced from the other active and passive remote sensing observations in the pollution plume are found to be in reasonable agreement. Level-2 aerosol products of CALIOP are consistent with our retrievals
Evaluating modelled tropospheric columns of CH , CO, and O in the Arctic using ground-based Fourier transform infrared (FTIR) measurements
This study evaluates tropospheric columns of methane, carbon monoxide, and ozone in the Arctic simulated by 11 models. The Arctic is warming at nearly 4 times the global average rate, and with changing emissions in and near the region, it is important to understand Arctic atmospheric composition and how it is changing. Both measurements and modelling of air pollution in the Arctic are difficult, making model validation with local measurements valuable. Evaluations are performed using data from five high-latitude ground-based Fourier transform infrared (FTIR) spectrometers in the Network for the Detection of Atmospheric Composition Change (NDACC). The models were selected as part of the 2021 Arctic Monitoring and Assessment Programme (AMAP) report on short-lived climate forcers. This work augments the modelâmeasurement comparisons presented in that report by including a new data source: column-integrated FTIR measurements, whose spatial and temporal footprint is more representative of the free troposphere than in situ and satellite measurements. Mixing
ratios of trace gases are modelled at 3-hourly intervals by CESM, CMAM, DEHM, EMEP MSC-W, GEM-
MACH, GEOS-Chem, MATCH, MATCH-SALSA, MRI-ESM2, UKESM1, and WRF-Chem for the years 2008, 2009, 2014, and 2015. The comparisons focus on the troposphere (0â7 km partial columns) at Eureka, Canada;
Thule, Greenland; Ny Ă
lesund, Norway; Kiruna, Sweden; and Harestua, Norway. Overall, the models are biased low in the tropospheric column, on average by â9.7 % for CH, â21 % for CO, and â18 % for O. Results for CH are relatively consistent across the 4 years, whereas CO has a maximum negative bias in the spring and minimum in the summer and O has a maximum difference centered around the summer. The average differences for the models are within the FTIR uncertainties for approximately 15 % of the modelâlocation comparisons
Overview : Integrative and Comprehensive Understanding on Polar Environments (iCUPE) - concept and initial results
The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project "iCUPE - integrative and Comprehensive Understanding on Polar Environments" to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.Peer reviewe
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Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) â concept and initial results
The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project âiCUPE â integrative and Comprehensive Understanding on Polar Environmentsâ to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Abstract
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and lowâmiddle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of âsingle-useâ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for lowâmiddle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both highâ and lowâmiddleâincome countries
Les aérosols en région arctique : origines, transport, interactions avec le rayonnement et les nuages
L'atmosphĂšre arctique, souvent perçue comme propre par le grand public, est en rĂ©alitĂ© rĂ©ceptrice de la pollution transportĂ©e rapidement depuis des sources lointaines aux moyennes latitudes. Un phĂ©nomĂšne emblĂ©matique qui la caractĂ©rise est la prĂ©sence frĂ©quente de couches dâaĂ©rosols depollution en Arctique en hiver et au printemps, dĂ©finissant la « brume arctique ». Câest une rĂ©gion oĂč les sources locales de pollution croissent rapidement et vont de pair avec de nouvelles opportunitĂ©s Ă©conomiques dâouverture de routes maritimes et dâexploitation de ressources naturelles.Les populations dâaĂ©rosols en Arctique sont complexes en raison de leurs variabilitĂ©s temporelle et verticale marquĂ©es et de leurs origines potentielles disparates. Les propriĂ©tĂ©s physicochimiques des aĂ©rosols dictent leurs impacts finaux sur le rayonnement et les nuages et celles-cidĂ©pendent des rĂ©gions sources. Les sources de pollution en Arctique ainsi que les processus de transport et de vieillissement conditionnent fortement les incertitudes relatives Ă la comprĂ©hension et la quantification de lâimpact des polluants sur lâenvironnement arctique. Nos Ă©tudes basĂ©es sur des simulations Ă mĂ©so-Ă©chelle et Ă©valuĂ©es par rapport aux observations in situ ou satellitaires ont Ă©tĂ© utilisĂ©es pour quantifier le rĂŽle des sources de pollution locales en Arctique, comme la navigation, les torchĂšres, la combustion domestique et lâinfluence du transport Ă longue distance des polluants depuis les latitudes moyennes ou subarctiques vers lâArctique. Les travaux publiĂ©s ont ciblĂ© prioritairement les conditions printaniĂšres et estivales dans le secteur du Nord de lâEurope, qui est fortement influencĂ© par les Ă©missions des activitĂ©s offshore et des bateaux, les Ă©missions industrielles sur le continent et le chauffage domestique, ainsi que le transport Ă longue distance depuis les rĂ©gions polluĂ©es en Europe centrale et les feux de biomasse en Asie et en SibĂ©rie. Ils ont mis en Ă©vidence que les sources locales dâaĂ©rosols et de leurs prĂ©curseurs ainsi que leurs impacts chimiques sur lâatmosphĂšre arctique Ă©taient particuliĂšrement mal quantifiĂ©es et que les masses dâair vieillies contenant des aĂ©rosols en provenance de sources de pollution distantes affectaient fortement la composition chimique, la qualitĂ© de lâair et le bilan radiatif en Arctique. Lâimpact relatif dĂ©pend fortement de la saison, du temps de rĂ©sidence et des chemins de transport vers lâArctique. Ces derniers sont trĂšs sensibles au passage du printemps Ă lâĂ©tĂ© en raison notamment des changements drastiques dans lâefficacitĂ© du lessivage humide des aĂ©rosols. La possibilitĂ© de prĂ©dire les manifestations du changement climatique en Arctique est sĂ©rieusement mise Ă mal par un manque de comprĂ©hension de processus clĂ©s en Arctique, notamment ceux liĂ©s aux nuages, aux aĂ©rosols et Ă leurs interactions. Les questions ne se limitent pas Ă la maniĂšre dont la rĂ©gion arctique rĂ©pond au changement global, mais couvrent aussi la façon dont le climat arctique est affectĂ© par les changements en cours dans la composition atmosphĂ©rique en Arctique
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