1. Satellite Data for Atmospheric Monitoring at the Pierre Auger ObservatoryA. Puyleart, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, published scientific conference contribution Abstract: Atmospheric monitoring over the 3000 km^2 of the Pierre Auger Observatory can be supplemented by satellite data. Methods for night-time cloud detection and aerosol cross-checking were created using the GOES-16 and Aeolus satellites, respectively. The geostationary GOES-16 satellite provides a 100% up-time view of the cloud cover over the observatory. GOES-13 was used until the end of 2017 for cloud monitoring, but with its retirement a method based on GOES-16 data was developed. The GOES-16 cloud detection method matches the observatory’s vertical laser cloud detection method at a rate of ∼90%. The Aeolus satellite crosses the Pierre Auger Observatory several times throughout the year firing UV-laser shots. The laser beams leave a track of scattered light in the atmosphere that can be observed by the light sensors of the observatory fluorescence telescopes. Using a parametric model of the aerosol concentration, the laser shots can be reconstructed with different combinations of the aerosol parameters. A minimization procedure then yields the parameter set that best describes the aerosol attenuation. Furthermore, the possibility of studying horizontal homogeneity of aerosols across the array is being investigated.
Keywords: Pierre Auger Observatory, indirect detection, fluorescence detection, ultra-high energy, cosmic rays, atmospheric monitoring, satellite monitoring, cloud detection, aerosols, UV laser shots
Published in RUNG: 04.10.2023; Views: 765; Downloads: 6
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2. Secondary organic aerosol formation from anthropogenic air pollution : rapid and higher than expectedRainer Volkamer, Jose L. Jimenez, F. M. San Martini, Katja Džepina, Q. Zhang, Dara Salcedo, Luisa T. Molina, D. Worsnop, 2006, original scientific article Abstract: The atmospheric chemistry of volatile organic compounds (VOCs) in urban areas results in the formation of 'photochemical smog', including secondary organic aerosol (SOA). State-of-the-art SOA models parameterize the results of simulation chamber experiments that bracket the conditions found in the polluted urban atmosphere. Here we show that in the real urban atmosphere reactive anthropogenic VOCs (AVOCs) produce much larger amounts of SOA than these models predict, even shortly after sunrise. Contrary to current belief, a significant fraction of the excess SOA is formed from first-generation AVOC oxidation products. Global models deem AVOCs a very minor contributor to SOA compared to biogenic VOCs (BVOCs). If our results are extrapolated to other urban areas, AVOCs could be responsible for additional 3 - 25 Tg yr(-1) SOA production globally, and cause up to - 0.1 W m(-2) additional top-of-the-atmosphere radiative cooling.
Keywords: atmospheric aerosol, atmospheric chemistry, volatile organic compounds, secondary organic aerosols
Published in RUNG: 12.04.2021; Views: 3007; Downloads: 0
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3. Technical note : use of a beam width probe in an aerosol mass spectrometer to monitor particle collection efficiency in the fieldDara Salcedo, T. B. Onasch, M. R. Canagaratna, Katja Džepina, J. A. Huffman, J. Jayne, D. Worsnop, C. E. Kolb, S. Weimer, F. Drewnick, 2007, original scientific article Abstract: Two Aerodyne Aerosol Mass Spectrometers (Q-AMS) were deployed in Mexico City, during the Mexico City Metropolitan Area field study (MCMA-2003) from 29 March - 4 May 2003 to investigate particle concentrations, sources, and processes. We report the use of a particle beam width probe (BWP) in the field to quantify potential losses of particles due to beam broadening inside the AMS caused by particle shape (nonsphericity) and particle size. Data from this probe show that no significant mass of particles was lost due to excessive beam broadening; i.e. the shape- and size-related collection efficiency (E-s) of the AMS during this campaign was approximately one. Comparison of the BWP data from MCMA-2003 with other campaigns shows that the same conclusion holds for several other urban, rural and remotes sites. This means that the aerodynamic lens in the AMS is capable of efficiently focusing ambient particles into a well defined beam and onto the AMS vaporizer for particles sampled in a wide variety of environments. All the species measured by the AMS during MCMA-2003 have similar attenuation profiles which suggests that the particles that dominate the mass concentration were internally mixed most of the time. Only for the smaller particles ( especially below 300 nm), organic and inorganic species show different attenuation versus particle size which is likely due to partial external mixing of these components. Changes observed in the focusing of the particle beam in time can be attributed, in part, to changes in particle shape (i.e. due to relative humidity) and size of the particles sampled. However, the relationships between composition, atmospheric conditions, and particle shape and size appear to be very complex and are not yet completely understood.
Keywords: atmospheric aerosol, organic aerosols, aerodynamic lenses, Mexico City
Published in RUNG: 11.04.2021; Views: 2618; Downloads: 0
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4. Ubiquity and dominance of oxygenated species in organic aerosols in anthropogenically-influenced Northern Hemisphere midlatitudesQ. Zhang, Jose L. Jimenez, M. R. Canagaratna, J. David Allan, H. Coe, I. M. Ulbrich, M. R. Alfarra, A. Takami, A. M. Middlebrook, Katja Džepina, 2007, original scientific article Abstract: Organic aerosol (OA) data acquired by the Aerosol Mass Spectrometer (AMS) in 37 field campaigns were deconvolved into hydrocarbon-like OA (HOA) and several types of oxygenated OA (OOA) components. HOA has been linked to primary combustion emissions (mainly from fossil fuel) and other primary sources such as meat cooking. OOA is ubiquitous in various atmospheric environments, on average accounting for 64%, 83% and 95% of the total OA in urban, urban downwind, and rural/remote sites, respectively. A case study analysis of a rural site shows that the OOA concentration is much greater than the advected HOA, indicating that HOA oxidation is not an important source of OOA, and that OOA increases are mainly due to SOA. Most global models lack an explicit representation of SOA which may lead to significant biases in the magnitude, spatial and temporal distributions of OA, and in aerosol hygroscopic properties.
Keywords: atmospheric aerosol, secondary organic aerosols, primary organic aerosols, aerodyne aerosol mass spectrometer
Published in RUNG: 11.04.2021; Views: 2064; Downloads: 0
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5. Ice cloud formation potential by free tropospheric particles from long-range transport over the Northern Atlantic OceanSwarup China, Peter A. Alpert, Bo Zhang, Simeon K. Schum, Katja Džepina, Kendra Wright, R. Chris Owen, Paulo Fialho, Lynn R. Mazzoleni, Claudio Mazzoleni, 2017, original scientific article Abstract: Long-range transported free tropospheric particles can play a significant role on heterogeneous ice nucleation. Using optical and electron microscopy we examine the physicochemical characteristics of ice nucleating particles (INPs). Particles were collected on substrates from the free troposphere at the remote Pico Mountain Observatory in the Azores Islands, after long-range transport and aging over the Atlantic Ocean. We investigate four specific events to study the ice formation potential by the collected particles with different ages and transport patterns. We use single-particle analysis, as well as bulk analysis to characterize particle populations. Both analyses show substantial differences in particle composition between samples from the four events; in addition, single-particle microscopy analysis indicates that most particles are coated
by organic material. The identified INPs contained mixtures of dust, aged sea salt and soot, and organic material acquired either at the source or during transport. The temperature and relative humidity (RH) at which ice formed, varied only by 5% between samples, despite differences in particle composition, sources, and transport patterns. We hypothesize that this small variation in the onset RH may be due to the coating material on the particles. This study underscores and motivates the need to further investigate how long-range transported and atmospherically aged free tropospheric particles impact ice cloud formation.
Keywords: atmospheric aerosols, ice nucleating particles, long-range transport, optical microscopy, electron microscopy, Pico Mountain Observatory
Published in RUNG: 11.04.2021; Views: 2331; Downloads: 133
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