5,104 results on '"Stohl, A."'
Search Results
202. Establishing Lagrangian connections between observations within air masses crossing the Atlantic during the International Consortium for Atmospheric Research on Transport and Transformation experiment
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Methven, J, Arnold, SR, Stohl, A, Evans, MJ, Avery, M, Law, K, Lewis, AC, Monks, PS, Parrish, DD, Reeves, CE, Schlager, H, Atlas, E, Blake, DR, Coe, H, Crosier, J, Flocke, FM, Holloway, JS, Hopkins, JR, McQuaid, J, Purvis, R, Rappenglück, B, Singh, HB, Watson, NM, Whalley, LK, and Williams, PI
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Meteorology & Atmospheric Sciences - Abstract
The ITCT-Lagrangian-2K4 (Intercontinental Transport and Chemical Transformation) experiment was conceived with an aim to quantify the effects of photochemistry and mixing on the transformation of air masses in the free troposphere away from emissions. To this end, attempts were made to intercept and sample air masses several times during their journey across the North Atlantic using four aircraft based in New Hampshire (USA), Faial (Azores) and Creil (France). This article begins by describing forecasts from two Lagrangian models that were used to direct the aircraft into target air masses. A novel technique then identifies Lagrangian matches between flight segments. Two independent searches are conducted: for Lagrangian model matches and for pairs of whole air samples with matching hydrocarbon fingerprints. The information is filtered further by searching for matching hydrocarbon samples that are linked by matching trajectories. The quality of these "coincident matches" is assessed using temperature, humidity and tracer observations. The technique pulls out five clear Lagrangian cases covering a variety of situations and these are examined in detail. The matching trajectories and hydrocarbon fingerprints are shown, and the downwind minus upwind differences in tracers are discussed. Copyright 2006 by the American Geophysical Union.
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- 2006
203. The 3‐Week‐Long Transport History and Deep Tropical Origin of the 2021 Extreme Heat Wave in the Pacific Northwest.
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Baier, K., Rubel, M., and Stohl, A.
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HEAT waves (Meteorology) ,ATMOSPHERIC transport ,AIR masses ,LATENT heat ,CONVEYOR belts ,WILDFIRES - Abstract
The heat wave in late June of 2021 (PNW21) set new temperature records in the Pacific Northwest (PNW). In Lytton the highest temperature ever recorded in Canada was measured. Several studies have already explored this extreme event in detail, however, here we compare the atmospheric air mass transport and heating processes associated with this heat wave with the 34 other most extreme heat events in the same region during the period 1960–2021, using a long backtracking time of 25 days. We found significant differences in the heat waves. During PNW21 most of the air was coming from the Philippine Sea, with more than 40% of the air located south of 15°N, and anomalous advection of sensible and latent heat from the Tropics was the dominant cause of PNW21. The latent heat was efficiently converted into sensible heat by precipitation, which was unique, as most other extremes experienced net diabatic cooling. Plain Language Summary: At the end of June in 2021 a heat wave occurred over the Pacific Northwest (PNW) and led to catastrophic damage in the region, notably the destruction of the town of Lytton by a wild fire 1 day after a new temperature record for Canada was set there. Here we look at where the air during this event was coming from and compare the atmospheric mass transport to 34 other extreme heat events in this region. We found that during the heat wave in June 2021 most of the air was coming from the Philippine Sea where it took up large amounts of heat and moisture. This source region is deeper in the Tropics than for all other extreme events. At the same time, the Philippine Sea was anomalously warm. Thus, the air was warmer and moister than for all the other extreme events already 3 weeks before reaching the PNW. The energy associated with the high tropical moisture content was efficiently converted into heat by precipitation along the Meiyu‐Baiu front—a unique process not found for any other extreme heat event. Key Points: The air causing the heat wave in late June 2021 (PNW21) came from deep in the Tropics, more south and west compared to other eventsThree weeks prior to the event, the air was warmer and moister, indicating that advection of heat from the Tropics was an important driverCondensation in a warm conveyor belt caused heating for PNW21, while most other extreme events showed overall diabatic cooling [ABSTRACT FROM AUTHOR]
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- 2023
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204. Contesting Human Rights
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Brysk, Alison, primary and Stohl, Michael, additional
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- 2019
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205. James Earl ‘Jimmy’ Carter Jr
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Stohl, Michael, primary
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- 2019
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206. Maternal and cord blood BAFF and APRIL levels during pregnancy
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Stohl, Hindi E., primary and Stohl, William, additional
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- 2022
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207. Factors in Prenatal Vaccine Knowledge and Uptake Among Minority Pregnant Patients [10C]
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Patapoff, Kelly E., Razi, Yasmine Y., Woods, Gabriella, Stohl, Hindi E., and Nelson, Anita L.
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- 2020
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208. A model of the post-implantation human embryo derived from pluripotent stem cells
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Weatherbee, Bailey AT, Gantner, Carlos W, Iwamoto-Stohl, Lisa K, Daza, Riza M, Hamazaki, Nobuhiko, Shendure, Jay, Zernicka-Goetz, Magdalena, Weatherbee, Bailey AT [0000-0002-6825-6278], Gantner, Carlos W [0000-0003-0825-7786], Daza, Riza M [0000-0003-1635-8675], Shendure, Jay [0000-0002-1516-1865], Zernicka-Goetz, Magdalena [0000-0002-7004-2471], and Apollo - University of Cambridge Repository
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1.1 Normal biological development and functioning ,1 Underpinning research ,32 Biomedical and Clinical Sciences ,Generic health relevance ,Stem Cell Research - Embryonic - Human ,3215 Reproductive Medicine ,Stem Cell Research - Abstract
The human embryo undergoes morphogenetic transformations following implantation into the uterus, yet our knowledge of this crucial stage is limited by the inability to observe the embryo in vivo. Stem cell-derived models of the embryo are important tools to interrogate developmental events and tissue-tissue crosstalk during these stages1. Here, we establish a model of the human post-implantation embryo, a human embryoid, comprised of embryonic and extraembryonic tissues. We combine two types of extraembryonic-like cells generated by transcription factor overexpression with wildtype embryonic stem cells and promote their self-organization into structures that mimic several aspects of the post-implantation human embryo. These self-organized aggregates contain a pluripotent epiblast-like domain surrounded by extraembryonic-like tissues. Our functional studies demonstrate that the epiblast-like domain robustly differentiates to amnion, extraembryonic mesenchyme, and primordial germ cell-like cells in response to BMP cues. In addition, we identify an inhibitory role for SOX17 in the specification of anterior hypoblast-like cells2. Modulation of the subpopulations in the hypoblast-like compartment demonstrated that extraembryonic-like cells impact epiblast-like domain differentiation, highlighting functional tissue-tissue crosstalk. In conclusion, we present a modular, tractable, integrated3 model of the human embryo that will allow us to probe key questions of human post-implantation development, a critical window when significant numbers of pregnancies fail.
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- 2023
209. Forest fire plumes sampled above Siberia during YAK-AEROSIB/POLARCAT airborne campaigns: properties and sources
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Paris, J. -D., Nedelec, P., Stohl, A., Arshinov, M. Yu., Belan, B. D., Ciais, P., Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire d'aérologie (LAERO), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
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[SDU]Sciences of the Universe [physics] - Abstract
International audience; The composition of the Siberian troposphere remains highly unknown due to a lack of measurements in this area. Siberia is a key region for a quantified understanding of many land-atmosphere exchange processes. As an example, Siberian forest fire emissions are a major extratropical source of CO to the atmosphere. Fire-emitted trace gases and particles are subject to long-range transport and may contribute to pollution of nearby Arctic. However, establishing precise top-down estimates of sources strengths based on satellite or surface network measurements for species such as CO is limited by models' ability to represent sub-grid-scale dynamics associated to the wildfire (pyroconvection) and the injection height of the plume. In an experimental effort to address this issue and to increase our knowledge of the properties of the Siberian troposphere, CO, O3, CO2 and fine particles were measured onboard a research aircraft in the frame of the YAK-AEROSIB project, partially as a contribution to the Summer 2008 POLARCAT programme. Two large scale transects were established over Northern and Central Siberia between 7 and 21 July 2008. The aircraft flight pattern consisted of ramp ascents and descents so as to sample as many vertical profiles as possible. Very high CO concentrations were observed at various altitudes, essentially in Eastern Siberia near Yakutsk and Chokurdakh. The highest concentrations (up to 600ppb) were observed between 2 and 5 km (flight ceiling being at 7km) in very thin layers (few hundreds of m thick). A Lagrangian modelling analysis (FLEXPART) revealed that the aircraft sampled fire plumes from regional fire emissions, east of Yakutsk, after about 2 days of transport. The observed fire plumes are also characterized by anomalies in O3 and excess particle concentrations. These data provide new constraints on our understanding of forest fire plume transport. They also constitute a critical testbench for the models used to assess pyrogenic emissions and to predict transport of pollution to the Arctic and at the global scale.
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- 2023
210. Turbulent dispersion of artificial SO2 puffs in the PBL from tomographic reconstructions of the concentration
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Ignacio Pisso, Massimo Cassiani, Arve Kylling, Kerstin Stebel, Norbert Schmidbauer, Andreas Stohl, Anna Solvejg Dinger, Hamidreza Ardeshiri, and Soon-Young Park
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Tomographic 3D reconstructions of artificial puff releases of SO2 were obtained from 2D images taken with UV cameras. These novel 3D reconstructions provide information on the distribution of concentration from a unique experimaental campaign dataset collected in Rena, Norway. The numerical solutions of the inverse problem of obtaining 3D reconstruction form 2D images were addressed with algebraic methods. Preliminary turbulence analysis of the puff concentration pdf, spatial moments, and 2-point statistics are presented. The experimentally obtained concentration pdf of a puff can be compared with different statistical models found in the literature. The time series of the puff spatial moments are obtained from the 3D concentration field directly in relative coordinates from observations. The distance-neighbour function can also be estimated directly from the 3d puff concentrations. The time series of 3D reconstructions of puffs entail promising posibilities for improving physical parametrizations in numerical dispersion models.
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- 2023
211. Gravitational settling of microplastic fibers: experimental results and implications for global transport
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Daria Tatsii, Gholamhossein Bagheri, Silvia Bucci, Lucie Bakels, and Andreas Stohl
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Gravitational settling is a crucial parameter to study the transport and distribution of atmospheric concentrations, sources, and sinks of particles. Although the settling velocity is highly dependent on the particle shape, most atmospheric transport models assume particles to be spherical, ignoring other geometries. In this study, we focus on the gravitational settling of microplastics (MP) particles, which often deviate strongly from sphericity. For instance, MP fibers can be approximated more closely by cylinders rather than spheres. Here, we present the results of conducted experiments with extremely elongated MP particles to define their settling velocity. This was done with the settling column and 3D-printed MP particles of different shapes (straight cylinders, half-circled cylinders, and quarter-circled cylinders), lengths, and aspect ratios. The experimental data shows that the parameterization scheme for shape correction proposed by Bagheri and Bonadonna, 2016 is a reliable tool to predict the gravitational settling of fibers considering different types of particle orientation (random, horizontal, and average of both).This scheme was implemented in the gravitational settling scheme of the Lagrangian transport model FLEXPART to eliminate uncertainties regarding the shape of a particle when simulating solid particle transport. As a study case, the mass concentration and deposition 3D fields of MP fibers were estimated according to the global population density to understand the contribution of the individual sites/regions to MP contamination of the atmosphere, land, and World Ocean.
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- 2023
212. Resuspension of microplastic particles from arid regions and global impacts on atmospheric concentrations and deposition
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Ioanna Evangelou, Daria Tatsii, Silvia Bucci, Christine Groot Zwaaftink, and Andreas Stohl
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Microplastic particles (MP), i.e., plastic particles with a size between 1 µm and 1 mm, have been detected in all compartments of the Earth system. While we are beginning to develop a quantitative understanding of the primary emissions of MPs such as tire wear, secondary sources from polluted environmental compartments such as the oceans and arid land surfaces, are currently not understood at all.In this study, we use reported MP concentrations in soils across the world combined with MP enrichment ratios (ER) in wind eroded sediments with respect to the soils (Bullard et al., 2021; Rezaei et al., 2019; Tian et al., 2022) and a population density map to estimate MP resuspension factors (RF) from arid regions. We then use global, 3-hourly dust emissions at 0.5o x 0.5o resolution from FLEXDUST (Groot Zwaaftink et al., 2016, 2017), as a proxy for the spatial and temporal variation of MPs emitted by arid regions. Scaled with the resuspension factors, we estimate the global MP resuspensions. To calculate the uncertainty of our emission model, we conduct a one-thousand-member Monte Carlo simulation with 14 different RF scenarios for each population category, perturbing the MP concentration in soils, the ER and the spatial scale used for the population density.We define, as a reference case, the emissions derived from the average ER, average soil concentrations and 50 km radius population categorization. These MP resuspension emissions are used as input to the Lagrangian atmospheric dispersion model FLEXPART (Pisso et al., 2019; Stohl et al., 2005) to simulate the global atmospheric cycle of resuspended MPs from arid regions. The simulations are driven by ERA5 meteorological fields at 0.5° horizontal resolution and 1-hour temporal resolution. We simulate the global atmospheric concentration and the deposition of resuspended MPs for different size distributions as well as shapes (spheres, fibers) of MPs. Lastly, we quantify the impact and compare it with observations, to estimate the importance of resuspension from arid regions for global MP abundance.
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- 2023
213. Sulfur hexafluoride emissions – critical remarks on inversion techniques and inverse model results for the past two decades
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Martin Vojta, Andreas Plach, Rona Thompson, and Andreas Stohl
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Inverse modeling provides a powerful tool to verify national greenhouse gas (GHG) emission inventories by using atmospheric observations. Often, inversions are based on Lagrangian Particle Dispersion Model simulations, where virtual particles are released from observation sites and traced backwards in time to establish a relationship between atmospheric concentrations and emission sources within the simulation period. The fact, that this simulation period is limited due to computational costs, raises two essential questions: (i) How to best define a baseline, that accounts for all emissions that occur prior to the simulation period? (ii) Which period length should be chosen for the backward-simulation?We show that often used statistical baseline methods have large problems and present a superior global-distribution-based (GDB) approach, that is consistent with the backward-simulation period, accounts for meteorological variability, and leads to inversion results that agree well with known global emission estimates. Our results further show, that longer backward-simulation periods beyond the often used 5 to 10 days increase the correlation between modeled and observed concentrations, and lead to more robust inversion results. Furthermore, they can help to better constrain emissions in regions poorly covered by the observation network.Based on these methodological results, we perform inversions for sulfur hexafluoride (SF6) - the most potent GHG regulated under the Kyoto Protocol with an estimated atmospheric lifetime of 3200 years. The inversions are based on 50-days backward-simulations, in-situ and flask measurements from various observation networks, and the GDB baseline method, to achieve globally and regionally consistent SF6 emissions from 2005 to present.
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- 2023
214. Using Satellite Column Observations with a Bayesian Inversion System for constraining the GHG budget over India
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Rona Thompson, Andreas Stohl, Martin Vojta, and RAKESH S
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The source-sink estimation of greenhouse gases and the accurate quantification of their flux distributions are a major scientific challenge of our times. Although statistically developed inventory-based carbon emissions improve understanding of emissions, they are uncertain and occasionally, they do not reflect actual emissions, especially at finer scales. By using GHG observations in conjunction with numerical atmospheric models, GHG budgets can be constrained. However, the sparseness in the in-situ observation networks of GHGs, makes this a challenging problem, especially in certain regions like India. However, satellite remote sensing can fill this data gap. This study applies the Bayesian inversion system, FLEXINVERT (Thompson and Stohl 2014), coupled with a Lagrangian Particle Dispersion Model, FLEXPART (Stohl et al 1998), to assimilate TROPOMI satellite observations of CH4 and constrains the CH4 fluxes over India domain. This inverse modeling system uses the Source-Receptor Relationship derived from Flexpart as the Transport operator while minimizing the cost function for optimization. The system will use various prior fluxes and initial concentration fields to test the set-up over Indian domain, which have strong fluxes of CH4 and are not well constrained by the existing ground-based measurement networks. The results will be compared with the limited in-situ observations available for the region.
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- 2023
215. Effects of deforestation events on atmospheric dynamics using Lagrangian reanalysis data
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Lucie Bakels, Silvia Bucci, and Andreas Stohl
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Deforestation in the Amazon basin has the potential to affect regional atmospheric circulations, possibly causing changes in the moisture transport by altering the regional Hadley and Walker cells (Zhang et al.1996). Previous studies that modelled the atmosphere under different extreme deforestation scenarios have shown that deforestation in the Amazon basin could increase the length and frequency of dry seasons in the Southern Amazon, while an increase of rain is expected in the Northern Amazon (e.g. Espinoza et al., 2019; Ruiz-Vasquez et al., 2020). Beyond climate models, it is also possible to trace the effect of past deforestation on the atmosphere using a Lagrangian transport model applied on atmospheric reanalysis data. Using the FLEXPART global simulations on the ERA-5 ECMWF reanalysis dataset (1959-2022), we are able to track air parcels through time and space, making it possible to locate the origin of moisture and latent heat, and quantify how global atmospheric circulation is affected by air transport from deforested areas.
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- 2023
216. The Role of Moisture and Heat Transport for Extreme Droughts in the Amazon Basin - a Lagrangian Perspective
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Katharina Baier and Andreas Stohl
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In the last decade, tropical rainforests, e.g. the Amazon basin, have experienced events of extreme droughts. Such events have huge impacts on the forest, as trees are damaged. Therefore, it is relevant to gain deeper understanding on the main mechanisms causing such events, and further clarify the role of moisture recycling over the continent vs. moisture transport from oceanic regions.We study the role of moisture- and heat transport for the Amazon basin, with special focus on drought events. We show how these extreme events differ from normal conditions, with special focus on the changes in atmospheric transport. We analyse the atmospheric transport with the particle dispersion model FLEXPART using meteorological input data from the ERA5 reanalysis. In this Lagrangian model, the atmosphere was filled homogeneously with particles, which were traced forward in time and represent the global atmospheric mass transport. From this Lagrangian reanalysis dataset, covering the years 1979-2021, air masses over the Amazon basin are selected and traced backward in time. Based on that, we investigate the role of continental and oceanic moisture source areas, incorporating also information on soil moisture and burned areas. Thereby, we highlight the relevance of moisture recycling over continental - vs. moisture transport from oceanic areas. For example, we found that for the northern parts of the Amazon basin the most important moisture source is the Atlantic Ocean, thus this area is less affected by deforestation in the southern areas.
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- 2023
217. Investigation of Concentration Fluctuations for continuous point sources by high resolution Large Eddy Simulation and Stochastic Modeling
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Massimo Cassiani, Hamidreza Ardeshiri, Ignacio Pisso, Pietro Salizzoni, Massimo Marro, Andreas Stohl, Kerstin Stebel, and Soon-Young Park
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Concentration fluctuations from continuous small sources in a neutral boundary layer were investigated by mean of high-resolution Large Eddy Simulation (LES). The data set includes concentration moments up to the fourth order and shows the range of validity of the Gamma probability density function (PDF) model for the concentration fluctuations and the transition to a Gaussian PDF for ground sources. We also investigated systematically the off-center line peaks in the concentration variance showing that they are persistent for ground level sources while they disappear according to theoretical arguments for elevated sources. The analysis includes a thorough investigation of the distribution of the most energetic components in the frequency domain by using spectral analysis of the LES results and a stochastic model based on simple theoretical arguments. This analysis supports the picture that the peak in concentration variance frequency distribution is related to both the plume dispersion geometry and the turbulent flow. The results also confirm the recent literature findings that for an elevated source the peak in the concentration variance frequency distribution is almost independent from the crosswind location for a given downwind distance from the source. To our knowledge no previous LES or wind tunnel study had the completeness of the current study.
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- 2023
218. United States Human Rights Policy and Foreign Assistance
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Apodaca, Clair and Stohl, Michael
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- 1999
219. Maternal and cord blood BAFF and APRIL levels during pregnancy
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Hindi E. Stohl and William Stohl
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Reproductive Medicine ,Immunology ,Obstetrics and Gynecology ,Immunology and Allergy - Abstract
Dysregulation of factors vital to the survival B cells and/or plasma cells, such as BAFF and APRIL, could be detrimental to a pregnancy.Serially collected first-, second-, and third-trimester serum samples were measured for BAFF and APRIL by ELISA from 150 pregnant women (71 healthy + 79 with a chronic medical disease) at a single medical center. Postpartum serum samples were also collected from the majority of these women. Matched third-trimester and cord blood samples were collected from 168 women (86 healthy + 82 with a chronic medical disease). Data were analyzed by chi-square statistic, unpaired t-test, paired t-test, Mann-Whitney rank sum test, Wilcoxon signed rank test, Spearman rank order correlation, and receiver operator characteristic (ROC) curve analyses as appropriate.Maternal serum BAFF levels declined as the pregnancies progressed and rebounded postpartum, whereas serum APRIL levels remained relatively flat throughout pregnancy and postpartum. Cord BAFF and APRIL levels correlated positively with gestation age and were considerably greater than the corresponding maternal third-trimester serum BAFF and APRIL levels, respectively. In women who developed preeclampsia, third-trimester BAFF levels were greater, rather than lower, than their corresponding second-trimester BAFF levels. ROC curve analysis suggested a potential role for third-trimester serum BAFF level as a biomarker of preeclampsia.BAFF and APRIL are differentially regulated in the mother during and following pregnancy, whereas each is upregulated in the developing fetus. An increase in third-trimester serum BAFF level may portend development of preeclampsia.
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- 2022
220. B cell-independent contribution of BAFF to murine autoimmune disease
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Stohl, William and Banfalvi, Agnes
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- 2016
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221. Oral Health Coverage Options for Pregnant Adults and Adolescents
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Stohl, Hindi E. and Chen, Amy
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Oral health -- Insurance ,Health insurance -- Methods ,Pregnant women -- Demographic aspects -- Health aspects ,Health care industry - Abstract
Oral health care is a necessary and critical component of health care for pregnant women, but its importance is often overlooked by clinicians. Pregnant women who are low-income also find it particularly difficult to access care. This analytic essay summarizes oral health coverage for pregnant women under various types of health insurance coverage, including Medicaid, the Children's Health Insurance Program, and coverage options available under the Affordable Care Act. We hope this information will help clinicians better understand the importance of oral health care during pregnancy and the range of coverage options that may be available to their patients., Author(s): Hindi E. Stohl [sup.1] , Amy Chen [sup.2] Author Affiliations: (1) UCLA David Geffen School of Medicine, Director of Perinatology, Harbor-UCLA Medical Center, 0000 0001 0157 6501, grid.239844.0, , [...]
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- 2018
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222. Substantial contribution of iodine to Arctic ozone destruction
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European Commission, Consejo Superior de Investigaciones Científicas (España), Academy of Finland, Ministry of Earth Sciences (India), Swiss National Science Foundation, Swiss Polar Institute, National Science Foundation (US), Ferring Pharmaceuticals, German Research Foundation, Mahajan, Anoop S. [0000-0002-2909-5432], Li, Qinyi [0000-0002-5146-5831], Cuevas, Carlos A. [0000-0002-9251-5460], Schmale, Julia [0000-0002-1048-7962], Angot, Hélène [0000-0003-4673-8249], Richter, Andreas [0000-0003-3339-212X], Fernandez, Rafael P. [0000-0002-4114-5500], Skov, Henrik [0000-0003-1167-8696], Bucci, Silvia [0000-0002-6251-9444], Duetsch, Marina [0000-0002-1128-4198], Stohl, Andreas [0000-0002-2524-5755], Archer, Stephen D. [0000-0001-6054-2424], Dada, Lubna [0000-0003-1105-9043], Daellenbach, Kaspar R. [0000-0003-1246-6396], Saiz-Lopez, A. [0000-0002-0060-1581], Benavent, Nuria, Mahajan, Anoop S., Li, Qinyi, Cuevas, Carlos A., Schmale, Julia, Angot, Hélène, Jokinen, Tuija, Quéléver, Lauriane L.J., Blechschmidt, Anne Marlene, Zilker, Bianca, Richter, Andreas, Serna, Jesús A., García-Nieto, D., Fernández, Rafael P., Skov, Henrik, Dumitrascu, Adela, Simões Pereira, Patric, Abrahamsson, Katarina, Bucci, Silvia, Duetsch, Marina, Stohl, Andreas, Beck, Ivo, Laurila, Tiia, Blomquist, Byron, Howard, Dean, Archer, Stephen D., Bariteau, Ludovic, Helmig, Detlev, Hueber, Jacques, Jacobi, Hans Werner, Posman, Kevin, Dada, Lubna, Daellenbach, Kaspar R., Saiz-Lopez, A., European Commission, Consejo Superior de Investigaciones Científicas (España), Academy of Finland, Ministry of Earth Sciences (India), Swiss National Science Foundation, Swiss Polar Institute, National Science Foundation (US), Ferring Pharmaceuticals, German Research Foundation, Mahajan, Anoop S. [0000-0002-2909-5432], Li, Qinyi [0000-0002-5146-5831], Cuevas, Carlos A. [0000-0002-9251-5460], Schmale, Julia [0000-0002-1048-7962], Angot, Hélène [0000-0003-4673-8249], Richter, Andreas [0000-0003-3339-212X], Fernandez, Rafael P. [0000-0002-4114-5500], Skov, Henrik [0000-0003-1167-8696], Bucci, Silvia [0000-0002-6251-9444], Duetsch, Marina [0000-0002-1128-4198], Stohl, Andreas [0000-0002-2524-5755], Archer, Stephen D. [0000-0001-6054-2424], Dada, Lubna [0000-0003-1105-9043], Daellenbach, Kaspar R. [0000-0003-1246-6396], Saiz-Lopez, A. [0000-0002-0060-1581], Benavent, Nuria, Mahajan, Anoop S., Li, Qinyi, Cuevas, Carlos A., Schmale, Julia, Angot, Hélène, Jokinen, Tuija, Quéléver, Lauriane L.J., Blechschmidt, Anne Marlene, Zilker, Bianca, Richter, Andreas, Serna, Jesús A., García-Nieto, D., Fernández, Rafael P., Skov, Henrik, Dumitrascu, Adela, Simões Pereira, Patric, Abrahamsson, Katarina, Bucci, Silvia, Duetsch, Marina, Stohl, Andreas, Beck, Ivo, Laurila, Tiia, Blomquist, Byron, Howard, Dean, Archer, Stephen D., Bariteau, Ludovic, Helmig, Detlev, Hueber, Jacques, Jacobi, Hans Werner, Posman, Kevin, Dada, Lubna, Daellenbach, Kaspar R., and Saiz-Lopez, A.
- Abstract
Unlike bromine, the effect of iodine chemistry on the Arctic surface ozone budget is poorly constrained. We present ship-based measurements of halogen oxides in the high Arctic boundary layer from the sunlit period of March to October 2020 and show that iodine enhances springtime tropospheric ozone depletion. We find that chemical reactions between iodine and ozone are the second highest contributor to ozone loss over the study period, after ozone photolysis-initiated loss and ahead of bromine.
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- 2022
223. Consistent estimation of polychotomous treatment effects with selection-bias and unobserved heterogeneity using panel data correlated random coefficients model
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Kawatkar, Aniket A., Hay, Joel W., Stohl, William, and Nichol, Michael B.
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- 2018
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224. Discrepancy between simulated and observed ethane and propane levels explained by underestimated fossil emissions
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Dalsøren, Stig B., Myhre, Gunnar, Hodnebrog, Øivind, Myhre, Cathrine Lund, Stohl, Andreas, Pisso, Ignacio, Schwietzke, Stefan, Höglund-Isaksson, Lena, Helmig, Detlev, Reimann, Stefan, Sauvage, Stéphane, Schmidbauer, Norbert, Read, Katie A., Carpenter, Lucy J., Lewis, Alastair C., Punjabi, Shalini, and Wallasch, Markus
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- 2018
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225. Bayesian inverse modeling and source location of an unintended 131I release in Europe in the fall of 2011
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O. Tichý, V. Šmídl, R. Hofman, K. Šindelářová, M. Hýža, and A. Stohl
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
In the fall of 2011, iodine-131 (131I) was detected at several radionuclide monitoring stations in central Europe. After investigation, the International Atomic Energy Agency (IAEA) was informed by Hungarian authorities that 131I was released from the Institute of Isotopes Ltd. in Budapest, Hungary. It was reported that a total activity of 342 GBq of 131I was emitted between 8 September and 16 November 2011. In this study, we use the ambient concentration measurements of 131I to determine the location of the release as well as its magnitude and temporal variation. As the location of the release and an estimate of the source strength became eventually known, this accident represents a realistic test case for inversion models. For our source reconstruction, we use no prior knowledge. Instead, we estimate the source location and emission variation using only the available 131I measurements. Subsequently, we use the partial information about the source term available from the Hungarian authorities for validation of our results. For the source determination, we first perform backward runs of atmospheric transport models and obtain source-receptor sensitivity (SRS) matrices for each grid cell of our study domain. We use two dispersion models, FLEXPART and Hysplit, driven with meteorological analysis data from the global forecast system (GFS) and from European Centre for Medium-range Weather Forecasts (ECMWF) weather forecast models. Second, we use a recently developed inverse method, least-squares with adaptive prior covariance (LS-APC), to determine the 131I emissions and their temporal variation from the measurements and computed SRS matrices. For each grid cell of our simulation domain, we evaluate the probability that the release was generated in that cell using Bayesian model selection. The model selection procedure also provides information about the most suitable dispersion model for the source term reconstruction. Third, we select the most probable location of the release with its associated source term and perform a forward model simulation to study the consequences of the iodine release. Results of these procedures are compared with the known release location and reported information about its time variation. We find that our algorithm could successfully locate the actual release site. The estimated release period is also in agreement with the values reported by IAEA and the reported total released activity of 342 GBq is within the 99 % confidence interval of the posterior distribution of our most likely model.
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- 2017
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226. Rainfall drives atmospheric ice-nucleating particles in the coastal climate of southern Norway
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F. Conen, S. Eckhardt, H. Gundersen, A. Stohl, and K. E. Yttri
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Ice-nucleating particles (INPs) active at modest supercooling (e.g. −8 °C; INP−8) can transform clouds from liquid to mixed phase, even at very small number concentrations (−3). Over the course of 15 months, we found very similar patterns in weekly concentrations of INP−8 in PM10 (median = 1.7 m−3, maximum = 10.1 m−3) and weekly amounts of rainfall (median = 28 mm, maximum = 153 mm) at Birkenes, southern Norway. Most INP−8 were probably aerosolised locally by the impact of raindrops on plant, litter and soil surfaces. Major snowfall and heavy rain onto snow-covered ground were not mirrored by enhanced numbers of INP−8. Further, transport model calculations for large (> 4 m−3) and small (−3) numbers of INP−8 revealed that potential source regions likely to provide precipitation to southern Norway were associated with large numbers of INP−8. The proportion of land cover and land use type in potential source regions was similar for large and small numbers of INP−8. In PM2. 5 we found consistently about half as many INP−8 as in PM10. From mid-May to mid-September, INP−8 correlated positively with the fungal spore markers arabitol and mannitol, suggesting that some fraction of INP−8 during that period may consist of fungal spores. In the future, warmer winters with more rain instead of snow may enhance airborne concentrations of INP−8 during the cold season in southern Norway and in other regions with a similar climate.
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- 2017
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227. Temporal and spatial variability of Icelandic dust emissions and atmospheric transport
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C. D. Groot Zwaaftink, Ó. Arnalds, P. Dagsson-Waldhauserova, S. Eckhardt, J. M. Prospero, and A. Stohl
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Icelandic dust sources are known to be highly active, yet there exist few model simulations of Icelandic dust that could be used to assess its impacts on the environment. We here present estimates of dust emission and transport in Iceland over 27 years (1990–2016) based on FLEXDUST and FLEXPART simulations and meteorological re-analysis data. Simulations for the year 2012 based on high-resolution operational meteorological analyses are used for model evaluation based on PM2. 5 and PM10 observations in Iceland. For stations in Reykjavik, we find that the spring period is well predicted by the model, while dust events in late fall and early winter are overpredicted. Six years of dust concentrations observed at Stórhöfði (Heimaey) show that the model predicts concentrations of the same order of magnitude as observations and timing of modelled and observed dust peaks agrees well. Average annual dust emission is 4.3 ± 0.8 Tg during the 27 years of simulation. Fifty percent of all dust from Iceland is on average emitted in just 25 days of the year, demonstrating the importance of a few strong events for annual total dust emissions. Annual dust emission as well as transport patterns correlate only weakly to the North Atlantic Oscillation. Deposition amounts in remote regions (Svalbard and Greenland) vary from year to year. Only limited dust amounts reach the upper Greenland Ice Sheet, but considerable dust amounts are deposited on Icelandic glaciers and can impact melt rates there. Approximately 34 % of the annual dust emission is deposited in Iceland itself. Most dust (58 %), however, is deposited in the ocean and may strongly influence marine ecosystems.
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- 2017
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228. Inverse modeling of the Chernobyl source term using atmospheric concentration and deposition measurements
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N. Evangeliou, T. Hamburger, A. Cozic, Y. Balkanski, and A. Stohl
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
This paper describes the results of an inverse modeling study for the determination of the source term of the radionuclides 134Cs, 137Cs and 131I released after the Chernobyl accident. The accident occurred on 26 April 1986 in the Former Soviet Union and released about 1019 Bq of radioactive materials that were transported as far away as the USA and Japan. Thereafter, several attempts to assess the magnitude of the emissions were made that were based on the knowledge of the core inventory and the levels of the spent fuel. More recently, when modeling tools were further developed, inverse modeling techniques were applied to the Chernobyl case for source term quantification. However, because radioactivity is a sensitive topic for the public and attracts a lot of attention, high-quality measurements, which are essential for inverse modeling, were not made available except for a few sparse activity concentration measurements far from the source and far from the main direction of the radioactive fallout. For the first time, we apply Bayesian inversion of the Chernobyl source term using not only activity concentrations but also deposition measurements from the most recent public data set. These observations refer to a data rescue attempt that started more than 10 years ago, with a final goal to provide available measurements to anyone interested. In regards to our inverse modeling results, emissions of 134Cs were estimated to be 80 PBq or 30–50 % higher than what was previously published. From the released amount of 134Cs, about 70 PBq were deposited all over Europe. Similar to 134Cs, emissions of 137Cs were estimated as 86 PBq, on the same order as previously reported results. Finally, 131I emissions of 1365 PBq were found, which are about 10 % less than the prior total releases. The inversion pushes the injection heights of the three radionuclides to higher altitudes (up to about 3 km) than previously assumed (≈ 2.2 km) in order to better match both concentration and deposition observations over Europe. The results of the present inversion were confirmed using an independent Eulerian model, for which deposition patterns were also improved when using the estimated posterior releases. Although the independent model tends to underestimate deposition in countries that are not in the main direction of the plume, it reproduces country levels of deposition very efficiently. The results were also tested for robustness against different setups of the inversion through sensitivity runs. The source term data from this study are publicly available.
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- 2017
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229. Aerosol indirect effects on the nighttime Arctic Ocean surface from thin, predominantly liquid clouds
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L. M. Zamora, R. A. Kahn, S. Eckhardt, A. McComiskey, P. Sawamura, R. Moore, and A. Stohl
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Aerosol indirect effects have potentially large impacts on the Arctic Ocean surface energy budget, but model estimates of regional-scale aerosol indirect effects are highly uncertain and poorly validated by observations. Here we demonstrate a new way to quantitatively estimate aerosol indirect effects on a regional scale from remote sensing observations. In this study, we focus on nighttime, optically thin, predominantly liquid clouds. The method is based on differences in cloud physical and microphysical characteristics in carefully selected clean, average, and aerosol-impacted conditions. The cloud subset of focus covers just ∼ 5 % of cloudy Arctic Ocean regions, warming the Arctic Ocean surface by ∼ 1–1.4 W m−2 regionally during polar night. However, within this cloud subset, aerosol and cloud conditions can be determined with high confidence using CALIPSO and CloudSat data and model output. This cloud subset is generally susceptible to aerosols, with a polar nighttime estimated maximum regionally integrated indirect cooling effect of ∼ −0.11 W m−2 at the Arctic sea ice surface (∼ 8 % of the clean background cloud effect), excluding cloud fraction changes. Aerosol presence is related to reduced precipitation, cloud thickness, and radar reflectivity, and in some cases, an increased likelihood of cloud presence in the liquid phase. These observations are inconsistent with a glaciation indirect effect and are consistent with either a deactivation effect or less-efficient secondary ice formation related to smaller liquid cloud droplets. However, this cloud subset shows large differences in surface and meteorological forcing in shallow and higher-altitude clouds and between sea ice and open-ocean regions. For example, optically thin, predominantly liquid clouds are much more likely to overlay another cloud over the open ocean, which may reduce aerosol indirect effects on the surface. Also, shallow clouds over open ocean do not appear to respond to aerosols as strongly as clouds over stratified sea ice environments, indicating a larger influence of meteorological forcing over aerosol microphysics in these types of clouds over the rapidly changing Arctic Ocean.
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- 2017
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230. A new aerosol wet removal scheme for the Lagrangian particle model FLEXPART v10
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H. Grythe, N. I. Kristiansen, C. D. Groot Zwaaftink, S. Eckhardt, J. Ström, P. Tunved, R. Krejci, and A. Stohl
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Geology ,QE1-996.5 - Abstract
A new, more physically based wet removal scheme for aerosols has been implemented in the Lagrangian particle dispersion model FLEXPART. It uses three-dimensional cloud water fields from the European Centre for Medium-Range Weather Forecasts (ECMWF) to determine cloud extent and distinguishes between in-cloud and below-cloud scavenging. The new in-cloud nucleation scavenging depends on cloud water phase (liquid, ice or mixed-phase), based on the aerosol's prescribed efficiency to serve as ice crystal nuclei and liquid water nuclei, respectively. The impaction scavenging scheme now parameterizes below-cloud removal as a function of aerosol particle size and precipitation type (snow or rain) and intensity.Sensitivity tests with the new scavenging scheme and comparisons with observational data were conducted for three distinct types of primary aerosols, which pose different challenges for modeling wet scavenging due to their differences in solubility, volatility and size distribution: (1) 137Cs released during the Fukushima nuclear accident attached mainly to highly soluble sulphate aerosol particles, (2) black carbon (BC) aerosol particles, and (3) mineral dust. Calculated e-folding lifetimes of accumulation mode aerosols for these three aerosol types were 11.7, 16.0, and 31.6 days respectively, when well mixed in the atmosphere. These are longer lifetimes than those obtained by the previous removal schem, and, for mineral dust in particular, primarily result from very slow in-cloud removal, which globally is the primary removal mechanism for these accumulation mode particles.Calculated e-folding lifetimes in FLEXPART also have a strong size dependence, with the longest lifetimes found for the accumulation-mode aerosols. For example, for dust particles emitted at the surface the lifetimes were 13.8 days for particles with 1 µm diameter and a few hours for 10 µm particles. A strong size dependence in below-cloud scavenging, combined with increased dry removal, is the primary reason for the shorter lifetimes of the larger particles. The most frequent removal is in-cloud scavenging (85 % of all scavenging events) but it occurs primarily in the free troposphere, while below-cloud removal is more frequent below 1000 m (52 % of all events) and can be important for the initial fate of species emitted at the surface, such as those examined here.For assumed realistic in-cloud removal efficiencies, both BC and sulphate have a slight overestimation of observed atmospheric concentrations (a factor of 1.6 and 1.2 respectively). However, this overestimation is largest close to the sources and thus appears more related to overestimated emissions rather than underestimated removal. The new aerosol wet removal scheme of FLEXPART incorporates more realistic information about clouds and aerosol properties and it compares better with both observed lifetimes and concentration than the old scheme.
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- 2017
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231. Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland
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M. Wittmann, C. D. Groot Zwaaftink, L. Steffensen Schmidt, S. Guðmundsson, F. Pálsson, O. Arnalds, H. Björnsson, T. Thorsteinsson, and A. Stohl
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Environmental sciences ,GE1-350 ,Geology ,QE1-996.5 - Abstract
Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ∼ 1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m−2. At the station located higher on the glacier ( ∼ 1525 m a.s.l.), the model produced nine dust events, with one single event causing ∼ 5 g m−2 of dust deposition and a total deposition of ∼ 10 g m−2 yr−1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of the 1.6 m w.e. melt in total) at the station located further upglacier. Our findings show that dust has a strong influence on the mass balance of glaciers in Iceland.
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- 2017
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232. Methane fluxes in the high northern latitudes for 2005–2013 estimated using a Bayesian atmospheric inversion
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R. L. Thompson, M. Sasakawa, T. Machida, T. Aalto, D. Worthy, J. V. Lavric, C. Lund Myhre, and A. Stohl
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
We present methane (CH4) flux estimates for 2005 to 2013 from a Bayesian inversion focusing on the high northern latitudes (north of 50° N). Our inversion is based on atmospheric transport modelled by the Lagrangian particle dispersion model FLEXPART and CH4 observations from 17 in situ and five discrete flask-sampling sites distributed over northern North America and Eurasia. CH4 fluxes are determined at monthly temporal resolution and on a variable grid with maximum resolution of 1° × 1°. Our inversion finds a CH4 source from the high northern latitudes of 82 to 84 Tg yr−1, constituting ∼ 15 % of the global total, compared to 64 to 68 Tg yr−1 (∼ 12 %) in the prior estimates. For northern North America, we estimate a mean source of 16.6 to 17.9 Tg yr−1, which is dominated by fluxes in the Hudson Bay Lowlands (HBL) and western Canada, specifically the province of Alberta. Our estimate for the HBL, of 2.7 to 3.4 Tg yr−1, is close to the prior estimate (which includes wetland fluxes from the land surface model, LPX-Bern) and to other independent inversion estimates. However, our estimate for Alberta, of 5.0 to 5.8 Tg yr−1, is significantly higher than the prior (which also includes anthropogenic sources from the EDGAR-4.2FT2010 inventory). Since the fluxes from this region persist throughout the winter, this may signify that the anthropogenic emissions are underestimated. For northern Eurasia, we find a mean source of 52.2 to 55.5 Tg yr−1, with a strong contribution from fluxes in the Western Siberian Lowlands (WSL) for which we estimate a source of 19.3 to 19.9 Tg yr−1. Over the 9-year inversion period, we find significant year-to-year variations in the fluxes, which in North America, and specifically in the HBL, appear to be driven at least in part by soil temperature, while in the WSL, the variability is more dependent on soil moisture. Moreover, we find significant positive trends in the CH4 fluxes in North America of 0.38 to 0.57 Tg yr−2, and northern Eurasia of 0.76 to 1.09 Tg yr−2. In North America, this could be due to an increase in soil temperature, while in North Eurasia, specifically Russia, the trend is likely due, at least in part, to an increase in anthropogenic sources.
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- 2017
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233. Preferential Expansion of Foxp3+ T Regulatory Cells in CTLA-4–Deficient and CTLA-4–Haploinsufficient C57BL/6 Mice
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William Stohl, Ning Yu, and Ying Wu
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Immunology ,Immunology and Allergy ,General Medicine - Abstract
Foxp3+ cells and CTLA-4 have been ascribed major roles in downregulating immune responses. To address the relationship between CTLA-4 expression and Foxp3+ cells, we generated littermate CTLA-4–sufficient (Ctla4+/+), CTLA-4–haploinsufficient (Ctla4+/−), and CTLA-4–deficient (Ctla4−/−) Foxp3-gfp knock-in C57BL/6 mice, permitting us to characterize the phenotype of Foxp3+ cells and to test their ex vivo T regulatory (Treg) suppressor activity. CD3+, CD4+, and CD8+ cells, but not CD19+ cells, were markedly expanded in Ctla4−/− mice compared with Ctla4+/+ or Ctla4+/− mice. In Ctla4−/− mice, the relative expansion of the Foxp3+ population was greater than that of the CD3+, CD4+, or CD8+ populations because of increased survival of Foxp3+ cells. Foxp3+ Treg cells from Ctla4−/− mice and Foxp3+ Treg cells from Ctla4+/+ mice exerted identical ex vivo suppressor function. This may be related to differential expression of GITR, CD73, and CD39 on Foxp3+ Treg cells from Ctla4−/− mice versus that on corresponding cells from littermate Ctla4+/+ or Ctla4+/− mice, with GITR and CD39 being upregulated and CD73 being downregulated on Foxp3+ Treg cells from Ctla4−/− mice. Moreover, CTLA-4 expression in Ctla4+/+, Ctla4+/−, and Ctla4−/− mice correlated with their percentages of Foxp3+ cells, suggesting an important role for CTLA-4 expression in Treg cell homeostasis. This may have vital ramifications for the treatment of patients for whom augmentation of suppressor function would be beneficial (e.g., patients with autoimmune diseases) and for whom diminution of suppressor function would be beneficial (e.g., patients with cancer).
- Published
- 2022
234. Postpartum gestational diabetes insipidus related to preeclampsia: A case report
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Goldrich, Alisa, primary, Yuan, Jessica, additional, and Stohl, Hindi, additional
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- 2023
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235. Oral Health Coverage Options for Pregnant Adults and Adolescents
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Stohl, Hindi E. and Chen, Amy
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- 2017
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236. Investigation of Concentration Fluctuations for continuous point sources by high resolution Large Eddy Simulation and Stochastic Modeling
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Cassiani, Massimo, primary, Ardeshiri, Hamidreza, additional, Pisso, Ignacio, additional, Salizzoni, Pietro, additional, Marro, Massimo, additional, Stohl, Andreas, additional, Stebel, Kerstin, additional, and Park, Soon-Young, additional
- Published
- 2023
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237. Gravitational settling of microplastic fibers: experimental results and implications for global transport
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Tatsii, Daria, primary, Bagheri, Gholamhossein, additional, Bucci, Silvia, additional, Bakels, Lucie, additional, and Stohl, Andreas, additional
- Published
- 2023
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238. Lagrangian modeling used for improving ice core interpretation
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Plach, Andreas, primary, Eckhardt, Sabine, additional, Pisso, Ignacio, additional, McConnell, Joseph R., additional, and Stohl, Andreas, additional
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- 2023
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239. Global microplastic emission and deposition fluxes at the ocean-atmosphere interface
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Bucci, Silvia, primary, Richon, Camille, additional, Bakels, Lucie, additional, and Stohl, Andreas, additional
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- 2023
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240. Turbulent dispersion of artificial SO2 puffs in the PBL from tomographic reconstructions of the concentration
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Pisso, Ignacio, primary, Cassiani, Massimo, additional, Kylling, Arve, additional, Stebel, Kerstin, additional, Schmidbauer, Norbert, additional, Stohl, Andreas, additional, Dinger, Anna Solvejg, additional, Ardeshiri, Hamidreza, additional, and Park, Soon-Young, additional
- Published
- 2023
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241. Effects of deforestation events on atmospheric dynamics using Lagrangian reanalysis data
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Bakels, Lucie, primary, Bucci, Silvia, additional, and Stohl, Andreas, additional
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- 2023
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242. Using Satellite Column Observations with a Bayesian Inversion System for constraining the GHG budget over India
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Subramanian, Rakesh, primary, Thompson, Rona, additional, Vojta, Martin, additional, and Stohl, Andreas, additional
- Published
- 2023
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243. Sulfur hexafluoride emissions – critical remarks on inversion techniques and inverse model results for the past two decades
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Vojta, Martin, primary, Plach, Andreas, additional, Thompson, Rona, additional, and Stohl, Andreas, additional
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- 2023
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244. The Role of Moisture and Heat Transport for Extreme Droughts in the Amazon Basin - a Lagrangian Perspective
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Baier, Katharina, primary and Stohl, Andreas, additional
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- 2023
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245. Resuspension of microplastic particles from arid regions and global impacts on atmospheric concentrations and deposition
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Evangelou, Ioanna, primary, Tatsii, Daria, additional, Bucci, Silvia, additional, Groot Zwaaftink, Christine, additional, and Stohl, Andreas, additional
- Published
- 2023
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246. Belimumab for the treatment of pediatric patients with lupus nephritis
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Stohl, William, primary and Kwok, Alyssa, additional
- Published
- 2023
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247. The offline Lagrangian particle model FLEXPART–NorESM/CAM (v1): model description and comparisons with the online NorESM transport scheme and with the reference FLEXPART model
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M. Cassiani, A. Stohl, D. Olivié, Ø. Seland, I. Bethke, I. Pisso, and T. Iversen
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Geology ,QE1-996.5 - Abstract
The offline FLEXible PARTicle (FLEXPART) stochastic dispersion model is currently a community model used by many scientists. Here, an alternative FLEXPART model version has been developed and tailored to use with the meteorological output data generated by the CMIP5-version of the Norwegian Earth System Model (NorESM1-M). The atmospheric component of the NorESM1-M is based on the Community Atmosphere Model (CAM4); hence, this FLEXPART version could be widely applicable and it provides a new advanced tool to directly analyse and diagnose atmospheric transport properties of the state-of-the-art climate model NorESM in a reliable way. The adaptation of FLEXPART to NorESM required new routines to read meteorological fields, new post-processing routines to obtain the vertical velocity in the FLEXPART coordinate system, and other changes. These are described in detail in this paper. To validate the model, several tests were performed that offered the possibility to investigate some aspects of offline global dispersion modelling. First, a comprehensive comparison was made between the tracer transport from several point sources around the globe calculated online by the transport scheme embedded in CAM4 and the FLEXPART model applied offline on output data. The comparison allowed investigating several aspects of the transport schemes including the approximation introduced by using an offline dispersion model with the need to transform the vertical coordinate system, the influence on the model results of the sub-grid-scale parameterisations of convection and boundary layer height and the possible advantage entailed in using a numerically non-diffusive Lagrangian particle solver. Subsequently, a comparison between the reference FLEXPART model and the FLEXPART–NorESM/CAM version was performed to compare the well-mixed state of the atmosphere in a 1-year global simulation. The two model versions use different methods to obtain the vertical velocity but no significant difference in the results was found. However, for both model versions there was some degradation in the well-mixed state after 1 year of simulation with the build-up of a bias and an increased scatter. Finally, the capability of the new combined modelling system in producing realistic, backward-in-time transport statistics was evaluated calculating the average footprint over a 5-year period for several measurement locations and by comparing the results with those obtained with the reference FLEXPART model driven by re-analysis fields. This comparison confirmed the effectiveness of the combined modelling system FLEXPART with NorESM in producing realistic transport statistics.
- Published
- 2016
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248. LS-APC v1.0: a tuning-free method for the linear inverse problem and its application to source-term determination
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O. Tichý, V. Šmídl, R. Hofman, and A. Stohl
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Geology ,QE1-996.5 - Abstract
Estimation of pollutant releases into the atmosphere is an important problem in the environmental sciences. It is typically formalized as an inverse problem using a linear model that can explain observable quantities (e.g., concentrations or deposition values) as a product of the source-receptor sensitivity (SRS) matrix obtained from an atmospheric transport model multiplied by the unknown source-term vector. Since this problem is typically ill-posed, current state-of-the-art methods are based on regularization of the problem and solution of a formulated optimization problem. This procedure depends on manual settings of uncertainties that are often very poorly quantified, effectively making them tuning parameters. We formulate a probabilistic model, that has the same maximum likelihood solution as the conventional method using pre-specified uncertainties. Replacement of the maximum likelihood solution by full Bayesian estimation also allows estimation of all tuning parameters from the measurements. The estimation procedure is based on the variational Bayes approximation which is evaluated by an iterative algorithm. The resulting method is thus very similar to the conventional approach, but with the possibility to also estimate all tuning parameters from the observations. The proposed algorithm is tested and compared with the standard methods on data from the European Tracer Experiment (ETEX) where advantages of the new method are demonstrated. A MATLAB implementation of the proposed algorithm is available for download.
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- 2016
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249. Wildfire influences on the variability and trend of summer surface ozone in the mountainous western United States
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X. Lu, L. Zhang, X. Yue, J. Zhang, D. A. Jaffe, A. Stohl, Y. Zhao, and J. Shao
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Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Increasing wildfire activities in the mountainous western US may present a challenge for the region to attain a recently revised ozone air quality standard in summer. Using current Eulerian chemical transport models to examine the wildfire ozone influences is difficult due to uncertainties in fire emissions, inadequate model chemistry, and resolution. Here we quantify the wildfire influence on the ozone variability, trends, and number of high MDA8 (daily maximum 8 h average) ozone days over this region in summers (June, July, and August) 1989–2010 using a new approach. We define a fire index using retroplumes (plumes of back-trajectory particles) computed by a Lagrangian dispersion model (FLEXPART) and develop statistical models based on the fire index and meteorological parameters to interpret MDA8 ozone concentrations measured at 13 Intermountain West surface sites. We show that the statistical models are able to capture the ozone enhancements by wildfires and give results with some features different from the GEOS-Chem Eulerian chemical transport model. Wildfires enhance the Intermountain West regional summer mean MDA8 ozone by 0.3–1.5 ppbv (daily episodic enhancements reach 10–20 ppbv at individual sites) with large interannual variability, which are strongly correlated with the total MDA8 ozone. We find large fire impacts on the number of exceedance days; for the 13 CASTNet sites, 31 % of the summer days with MDA8 ozone exceeding 70 ppbv would not occur in the absence of wildfires.
- Published
- 2016
- Full Text
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250. A full year of aerosol size distribution data from the central Arctic under an extreme positive Arctic Oscillation : insights from the Multidisciplinarydrifting Observatory for the Study of Arctic Climate (MOSAiC) expedition
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Boyer, Matthew, Aliaga, Diego, Pernov, Jakob Boyd, Angot, Hélène, Quéléver, Lauriane L. J., Dada, Lubna, Heutte, Benjamin, Dall'Osto, Manuel, Beddows, David C. S., Brasseur, Zoé, Beck, Ivo, Bucci, Silvia, Duetsch, Marina, Stohl, Andreas, Laurila, Tiia, Asmi, Eija, Massling, Andreas, Thomas, Daniel Charles, Klenø Nøjgaard, Jakob, Chan, Tak, Sharma, Sangeeta, Tunved, Peter, Krejci, Radovan, Hansson, Hans-Christen, Bianchi, Federico, Lehtipalo, Katrianne, Wiedensohler, Alfred, Weinhold, Kay, Kulmala, Markku, Petäjä, Tuukka, Sipilä, Mikko, Schmale, Julia, Jokinen, Tuija, Boyer, Matthew, Aliaga, Diego, Pernov, Jakob Boyd, Angot, Hélène, Quéléver, Lauriane L. J., Dada, Lubna, Heutte, Benjamin, Dall'Osto, Manuel, Beddows, David C. S., Brasseur, Zoé, Beck, Ivo, Bucci, Silvia, Duetsch, Marina, Stohl, Andreas, Laurila, Tiia, Asmi, Eija, Massling, Andreas, Thomas, Daniel Charles, Klenø Nøjgaard, Jakob, Chan, Tak, Sharma, Sangeeta, Tunved, Peter, Krejci, Radovan, Hansson, Hans-Christen, Bianchi, Federico, Lehtipalo, Katrianne, Wiedensohler, Alfred, Weinhold, Kay, Kulmala, Markku, Petäjä, Tuukka, Sipilä, Mikko, Schmale, Julia, and Jokinen, Tuija
- Abstract
The Arctic environment is rapidly changing due to accelerated warming in the region. The warming trend is driving a decline in sea ice extent, which thereby enhances feedback loops in the surface energy budget in the Arctic. Arctic aerosols play an important role in the radiative balance and hence the climate response in the region, yet direct observations of aerosols over the Arctic Ocean are limited. In this study, we investigate the annual cycle in the aerosol particle number size distribution (PNSD), particle number concentration (PNC), and black carbon (BC) mass concentration in the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. This is the first continuous, year-long data set of aerosol PNSD ever collected over the sea ice in the central Arctic Ocean. We use a k-means cluster analysis, FLEXPART simulations, and inverse modeling to evaluate seasonal patterns and the influence of different source regions on the Arctic aerosol population. Furthermore, we compare the aerosol observations to land-based sites across the Arctic, using both long-term measurements and observations during the year of the MOSAiC expedition (2019–2020), to investigate interannual variability and to give context to the aerosol characteristics from within the central Arctic. Our analysis identifies that, overall, the central Arctic exhibits typical seasonal patterns of aerosols, including anthropogenic influence from Arctic haze in winter and secondary aerosol processes in summer. The seasonal pattern corresponds to the global radiation, surface air temperature, and timing of sea ice melting/freezing, which drive changes in transport patterns and secondary aerosol processes. In winter, the Norilsk region in Russia/Siberia was the dominant source of Arctic haze signals in the PNSD and BC observations, which contributed to higher accumulation-mode PNC and BC mass concentrations in the central Arctic than at land-based obse
- Published
- 2023
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