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Optical properties and simple forcing efficiency of the organic aerosols and black carbon emitted by residential wood burning in rural Central Europe
Andrea Cuesta-Mosquera, Kristina Glojek, Griša Močnik, Luka Drinovec, Asta Gregorič, Martin Rigler, Matej Ogrin, Baseerat Romshoo, Kay Weinhold, Maik Merkel, 2024, original scientific article

Abstract: Abstract. Recent years have seen an increase in the use of wood for energy production of over 30 %, and this trend is expected to continue due to the current energy crisis and geopolitical instability. At present, residential wood burning (RWB) is one of the most important sources of organic aerosols (OA) and black carbon (BC). While BC is recognized for its large light absorption cross-section, the role of OA in light absorption is still under evaluation due to their heterogeneous composition and source-dependent optical properties. Studies that characterize wood-burning aerosol emissions in Europe typically focus on urban and background sites and only cover BC properties. However, RWB is more prevalent in rural areas, and the present scenario indicates that an improved understanding of the RWB aerosol optical properties and their subsequent connection to climate impacts is necessary for rural areas. We have characterized atmospheric aerosol particles from a central European rural site during wintertime in the village of Retje in Loški Potok, Slovenia, from 01.12.2017 to 07.03.2018. The village experienced extremely high aerosol concentrations produced by RWB and near-ground temperature inversion. The isolated location of the site and the substantial local emissions made it an ideal laboratory-like place for characterizing RWB aerosols with low influence from non-RWB sources under ambient conditions. The mean mass concentrations of OA and BC were 34.8 µg m-3 (max = 271.8 µg m-3) and 3.1 µg m-3 (max = 24.3 µg m-3), respectively. The mean total particle number concentration (10–600 nm) was 9.9 x 103 particles cm-3 (max = 53.5 x 103 particles cm-3). The mean total light absorption coefficient at 370 nm and 880 nm measured by an Aethalometer AE33 were 122.8 Mm-1 and 15.3 Mm-1 and had maximum values of 1103.9 Mm-1 and 179.1 Mm-1, respectively. The aerosol concentrations and absorption coefficients measured during the campaign in Loški Potok were significantly larger than those reported values for several urban areas in the region with larger populations and extent of aerosol sources. Here, considerable contributions from brown carbon (BrC) to the total light absorption were identified, reaching up to 60 % and 48 % in the near UV (370 nm) and blue (470 nm) wavelengths. These contributions are up to three times higher than values reported for other sites impacted by wood-burning emissions. The calculated mass absorption cross-section and the absorption Ångström exponent for RWB OA were MACOA, 370 nm= 2.4 m2 g-1, and AAEBrC, 370–590 nm= 3.9, respectively. Simple forcing efficiency (SFE) calculations were performed as a sensitivity analysis to evaluate the climate impact of the RWB aerosols produced at the study site by integrating the optical properties measured during the campaign. The SFE results show a considerable forcing capacity from the local RWB aerosols, with a high sensitivity to OA absorption properties and a more substantial impact over bright surfaces like snow, typical during the coldest season with higher OA emissions from RWB. Our study's results are highly significant regarding air pollution, optical properties, and climate impact. The findings suggest that there may be an underestimation of RWB emissions in rural Europe and that further investigation is necessary.
Keywords: wood-burning aerosols, optical characterization, black carbon, rural areas
Published in RUNG: 10.01.2024; Views: 752; Downloads: 6
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Characterization of atmospheric properties over the Cherenkov Telescope Array at La Palma
Miha Živec, doctoral dissertation

Abstract: Imaging Atmospheric Cherenkov Telescope (IACT) systems are used in high-energy astrophysics to detect and study gamma-ray sources in the universe. These telescopes measure properties of cosmic gamma rays using Cherenkov radiation emitted by secondary particles produced after interacting with the Earth’s atmosphere. Atmospheric monitoring is crucial for the proper operation of IACT systems. A number of remote sensing and in situ methods are used to understand and correct the effects of the atmosphere on the propagation of Cherenkov radiation from its origin to the telescope. Failure to do so greatly decreases IACT performance, particularly, their energy resolution and threshold. Lidar systems can be used to measure atmospheric optical depth profiles, which are essential for IACT calibration. The main aim of this thesis is to demonstrate that a prototype lidar for the north-ern site of the Cherenkov Telescope Array Observatory (CTAO), which is a next-generation IACT now under construction, has hardware and software capabilities that would lead to the construction of CTAO Raman lidar. Due to specific require-ments of the CTAO, a Raman lidar, which can provide better atmospheric parameter accuracy, will be used for the first time in an IACT system. In 2021-2022 the BRL was deployed to the future CTAO-North site at the Roque de los Muchachos observatory, La Palma, for testing in its actual operating conditions. During a year and a half long test period, it underwent a number of tests, including manual and remote operation under various environmental conditions. These included hot summers, cold winters, rain, snow, ice, and strong winds, but also some more exotic events, such as desert sand intrusions (Calima) and volcanic eruptions. The latter two are presented in this work as test cases for atmospheric characterization. Since the main goal of a CTAO lidar is the optical depth measurements, the BRL does not have the full set of features for aerosol characterization. While it can yield the ˚Angstr¨om exponent and lidar ratio, it does not provide depolarization informa-tion, which is one of the key components for aerosol typing. As the atmosphere at La Palma was found to be more complex than initially anticipated, we present the benefits of including depolarization capability by using a conceptually similar Raman lidar system specifically designed for aerosol characterization. We present the results of a campaign focused on the determination of bioaerosol capabilities to act as cloud condensation nuclei and ice-nucleating particles in mixed-phase clouds, where depo-larization information was used to determine the thermodynamic phase of the cloud.
Keywords: Cherenkov Telescope Array Observatory, Raman Lidar, atmospheric optical depth, aerosol characterization, Cumbre Vieja, Calima
Published in RUNG: 23.10.2023; Views: 933; Downloads: 33
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