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1.
An overview of the ASKOS campaign in Cabo Verde
Eleni Marinou, Peristera Paschou, Ioanna Tsikoudi, Alexandra Tsekeri, Vasiliki Daskalopoulou, Dimitra Kouklaki, Nikos Siomos, Vasileios Spanakis-Misirlis, Kalliopi Artemis Voudouri, Griša Močnik, Jesús Yus-Díez, 2023, objavljeni znanstveni prispevek na konferenci

Opis: In the framework of the ESA-NASA Joint Aeolus Tropical Atlantic Campaign (JATAC), the ASKOS experiment was implemented during the summer and autumn of 2021 and 2022. ASKOS comprised roughly 9 weeks of measurements in the Saharan dust outflow towards the North Atlantic, with operations conducted from the Cabo Verde Islands. Through its unprecedented dataset of synergistic measurements in the region, ASKOS will allow for the calibration and validation of the aerosol/cloud product from Aeolus and the preparation of the terrain for EarthCARE cal/val activities. Moreover, ASKOS marks a turning point in our ability to study Saharan dust properties and the processes affecting its atmospheric transport, as well as the link to other components of the Earth’s system, such as the effect of dust particles on cloud formation over the Eastern Atlantic and the effect of large and giant particles on radiation. This is possible through the synergy of diverse observations acquired during the experiment, which include intense 24/7 ground-based aerosol, cloud, wind, and radiation remote sensing measurements, and UAV-based aerosol in situ measurements within the Saharan air layer, up to 5.3 km altitude, offering particle size-distributions up to 40 μm as well as sample collection for mineralogical analysis. We provide an outline of the novel measurements along with the main scientific objectives of ASKOS. The campaign data will be publicly available by September of 2023 through the EVDC portal (ESA Validation Data Center).
Ključne besede: experimental campaign, remote sensing, lidar, radar, radiosondes, radiation, desert dust
Objavljeno v RUNG: 25.09.2023; Ogledov: 618; Prenosov: 5
.pdf Celotno besedilo (4,87 MB)
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2.
Implementation of a Markov Chain Monte Carlo method to inorganic aerosol modeling of observations from the MCMA-2003 campaign : part II
F. M. San Martini, E. J. Dunlea, R. M. Volkamer, T. B. Onasch, J. Jayne, M. R. Canagaratna, D. Worsnop, C. E. Kolb, J. H. Shorter, Katja Džepina, 2006, izvirni znanstveni članek

Opis: A Markov Chain Monte Carlo model for integrating the observations of inorganic species with a thermodynamic equilibrium model was presented in Part I of this series. Using observations taken at three ground sites, i. e. a residential, industrial and rural site, during the MCMA-2003 campaign in Mexico City, the model is used to analyze the inorganic particle and ammonia data and to predict gas phase concentrations of nitric and hydrochloric acid. In general, the model is able to accurately predict the observed inorganic particle concentrations at all three sites. The agreement between the predicted and observed gas phase ammonia concentration is excellent. The NOz concentration calculated from the NOy, NO and NO2 observations is of limited use in constraining the gas phase nitric acid concentration given the large uncertainties in this measure of nitric acid and additional reactive nitrogen species. Focusing on the acidic period of 9-11 April identified by Salcedo et al. ( 2006), the model accurately predicts the particle phase observations during this period with the exception of the nitrate predictions after 10: 00 a. m. ( Central Daylight Time, CDT) on 9 April, where the model underpredicts the observations by, on average, 20%. This period had a low planetary boundary layer, very high particle concentrations, and higher than expected nitrogen dioxide concentrations. For periods when the particle chloride observations are consistently above the detection limit, the model is able to both accurately predict the particle chloride mass concentrations and provide well-constrained HCl ( g) concentrations. The availability of gas-phase ammonia observations helps constrain the predicted HCl ( g) concentrations. When the particles are aqueous, the most likely concentrations of HCl ( g) are in the sub-ppbv range. The most likely predicted concentration of HCl ( g) was found to reach concentrations of order 10 ppbv if the particles are dry. Finally, the atmospheric relevance of HCl ( g) is discussed in terms of its indicator properties for the possible influence of chlorine-mediated photochemistry in Mexico City.
Ključne besede: secondary organic aerosols, Mexico City, MCMA-2003 field campaign, thermodynamic equilibrium
Objavljeno v RUNG: 11.04.2021; Ogledov: 2100; Prenosov: 0
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3.
Comparative Analysis of urban atmospheric aerosol by particle-induced X-ray emission (PIXE), proton elastic scattering analysis (PESA), and aerosol mass spectrometry (AMS)
K.S. Johnson, A. Laskin, Jose L. Jimenez, V. Shutthanandan, Luisa T. Molina, Dara Salcedo, Katja Džepina, Mario J. Molina, 2008, izvirni znanstveni članek

Opis: A multifaceted approach to atmospheric aerosol analysis is often desirable infield studies where an understanding of technical comparability among different measurement techniques is essential. Herein, we report quantitative intercomparisons of particle-induced X-ray emission (PIXE) and proton elastic scattering analysis (PESA), performed offline under a vacuum, with analysis by aerosol mass spectrometry (AMS) carried out in real-time during the MCMA-2003 Field Campaign in the Mexico City Metropolitan Area. Good agreement was observed for mass concentrations of PIXE-measured sulfur (assuming it was dominated by SO42-) and AMS-measured sulfate during most of the campaign. PESA-measured hydrogen mass was separated into sulfate H and organic H mass fractions, assuming the only major contributions were (NH4)(2)SO4 and organic compounds. Comparison of the organic H mass with AMS organic aerosol measurements indicates that about 75% of the mass of these species evaporated under a vacuum. However similar to 25% of the organics does remain under a vacuum, which is only possible with low-vapor-pressure compounds, and which supports the presence of high-molecular-weight or highly oxidized organics consistent with atmospheric aging. Approximately 10% of the chloride detected by AMS was measured by PIXE, possibly in the form of metal-chloride complexes, while the majority of Cl was likely present as more volatile species including NH4Cl. This is the first comparison of PIXE/PESA and AMS and, to our knowledge, also the first report of PESA hydrogen measurements for urban organic aerosols.
Ključne besede: organic aerosols, secondary organic aerosols, Mexico City, MCMA-2003 field campaign
Objavljeno v RUNG: 11.04.2021; Ogledov: 2135; Prenosov: 0
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4.
Modeling the multiday evolution and aging of secondary organic aerosol during MILAGRO 2006
Katja Džepina, Christopher D. Cappa, Rainer Volkamer, Sasha Madronich, Peter F. DeCarlo, Rahul A. Zaveri, Jose L. Jimenez, 2011, izvirni znanstveni članek

Opis: In this study, we apply several recently proposed models to the evolution of secondary organic aerosols (SOA) and organic gases advected from downtown Mexico City at: an altitude of similar to 3.5 km during three days of aging, in a way that is directly comparable to simulations in regional and global models. We constrain the model with and compare its results to available observations. The model SOA formed from oxidation of volatile organic compounds (V-SOA) when using a non-aging SOA parameterization cannot explain the observed SOA concentrations in aged pollution, despite the increasing importance of the low-NO, channel. However, when using an aging SOA parameterization, V-SOA alone is similar to the regional aircraft observations, highlighting the wide diversity in current V-SOA formulations. When the SOA formed from oxidation of semivolatile and intermediate volatility organic vapors (SI-SOA) is computed following Robinson et al. (2007) the model matches the observed SOA mass, but its 0/C is similar to 2 x too low. With the parameterization of Grieshop et al. (2009), the total SOA mass is similar to 2 x too high, but 0/C and volatility are closer to the observations. Heating or dilution cause the evaporation of a substantial fraction of the model SOA; this fraction is reduced by aging although differently for heating vs dilution. Lifting of the airmass to the free-troposphere during dry convection substantially increases SOA by condensation of semivolatile vapors; this effect is reduced by aging.
Ključne besede: Mexico-city, volatility, semivolatile, transport, campaign
Objavljeno v RUNG: 11.04.2021; Ogledov: 1886; Prenosov: 0
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