Auflistung nach Autor:in "Wehner, Birgit"

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Evaluation of the size segregation of elemental carbon (EC) emission in Europe: influence on the simulation of EC long-range transportation
(2016) Chen, Ying-Yuan; Birmili, Wolfram; Cheng, Ya-Fang; Denier van der Gon, Hugo A.C.; Ma, Nan; Wolke, Ralf; Nordmann, Stephan; Wehner, Birgit; Sun, Jia; Spindler, Gerald; Mu, Qing; Pöschl, Ulrich; Su, Hang; Wiedensohler, Alfred
Elemental Carbon (EC) has a significant impact on human health and climate change. In order to evaluate the size segregation of EC emission in the EUCAARI inventory and investigate its influence on the simulation of EC long-range transportation in Europe, we used the fully coupled online Weather Research and Forecasting/Chemistry model (WRF-Chem) at a resolution of 2 km focusing on a region in Germany, in conjunction with a high-resolution EC emission inventory. The ground meteorology conditions, vertical structure and wind pattern were well reproduced by the model. The simulations of particle number and/or mass size distributions were evaluated with observations at the central European background site Melpitz. The fine mode particle concentration was reasonably well simulated, but the coarse mode was substantially overestimated by the model mainly due to the plume with high EC concentration in coarse mode emitted by a nearby point source. The comparisons between simulated EC and Multi-angle Absorption Photometers (MAAP) measurements at Melpitz, Leipzig-TROPOS and Bösel indicated that the coarse mode EC (ECc) emitted from the nearby point sources might be overestimated by a factor of 2-10. The fraction of ECc was overestimated in the emission inventory by about 10-30 % for Russia and 5-10 % for Eastern Europe (e.g., Poland and Belarus). This incorrect size-dependent EC emission results in a shorter atmospheric life time of EC particles and inhibits the long-range transport of EC. A case study showed that this effect caused an underestimation of 20-40 % in the EC mass concentration in Germany under eastern wind pattern.Quelle: http://www.atmos-chem-phys.net
Indoor/outdoor relationship of fine and ultrafine particles
(2018) Zhao, Jiangyue; Wehner, Birgit; Tuch, Thomas; Daniels, Anja; Birmili, Wolfram
Particle mass concentrations and number size distributions in 40 Homes in Germany: Indoor-to-outdoor relationships, diurnal and seasonal variation
(2020) Zhao, Jiangyue; Birmili, Wolfram; Daniels, Anja; Wehner, Birgit
Few studies investigated residential particle concentration levels with a full picture of aerosol particles from 10 nm to 10 Ìm size range with size-resolved information, and none was performed in central Europe in the long-term in multiple homes. To capture representative diurnal and seasonal patterns of exposure to particles, and investigate the driving factors to their variations, measurements were performed in 40 homes for around two weeks each in Leipzig and Berlin, Germany. These over 500 days' measurements combined PM10 and PM2.5 mass concentrations, particle number concentration and size distribution (PNC and PNSD, 10-800 nm), CO2 concentration, and residential activities diary into a unique dataset. Natural ventilation was dominated, the mean ventilation rate calculated from CO2 measurements was 0.2 h-1 and 3.7 h-1 with closed and opened windows, respectively. The main findings of this study showed that, the residents in German homes were exposed to a significantly higher mass concentration of coarse particles than outdoors, thus indoor exposure to coarse particles cannot be described by outdoors. The median indoor PNC diurnal cycles were generally lower than outdoors (median I/O ratio 0.69). However, indoor exposure to particles was different in the cold and warm season. In the warm season, due to longer opening window periods, indoor sources' contribution was weakened, which also resulted in the indoor PNC and PNSD being very similar to the outdoors. In the cold season, indoor sources caused strong peaks of indoor PNC that exceeded outdoors, along with the relatively low penetration factor - 0.5 for all size ranges, and indoor particle losses, which was particularly effective in reducing the ultrafine PNC, resulting in a different particle exposure load than outdoors. This study provides a detailed understanding of residential particle exposure in multiple homes, facilitating future studies to assess health effects in residential environments. Quelle. https://aaqr.org/
Sea salt emission, transport and influence on size-segregated nitrate simulation: a case study in northwestern Europe by WRF-Chem
(2016) Chen, Ying-Yuan; Barthel, Stefan; Cheng, Yafang; Birmili, Wolfram; Ma, Nan; Wolke, Ralf; Schüttauf, Stephanie; Ran, Liang; Wehner, Birgit; Nordmann, Stephan; Denier van der Gon, Hugo A.C.; Mu, Quing; Spindler, Gerald; Stieger, Bastian; Müller, Konrad; Zheng, Guang-Jie; Pöschl, Ulrich; Su, Hang; Wiedensohler, Alfred
Sea salt aerosol (SSA) is one of the major components of primary aerosols and has significant impact on the formation of secondary inorganic particles mass on a global scale. In this study, the fully online coupled WRF-Chem model was utilized to evaluate the SSA emission scheme and its influence on the nitrate simulation in a case study in Europe during 10-20 September 2013. Meteorological conditions near the surface, wind pattern and thermal stratification structure were well reproduced by the model. Nonetheless, the coarse-mode (PM1?-?10) particle mass concentration was substantially overestimated due to the overestimation of SSA and nitrate. Compared to filter measurements at four EMEP stations (coastal stations: Bilthoven, Kollumerwaard and Vredepeel; inland station: Melpitz), the model overestimated SSA concentrations by a factor of 8-20. We found that this overestimation was mainly caused by overestimated SSA emissions over the North Sea during 16-20 September. Over the coastal regions, SSA was injected into the continental free troposphere through an "aloft bridgeŁ (about 500 to 1000?m above the ground), a result of the different thermodynamic properties and planetary boundary layer (PBL) structure between continental and marine regions. The injected SSA was further transported inland and mixed downward to the surface through downdraft and PBL turbulence. This process extended the influence of SSA to a larger downwind region, leading, for example, to an overestimation of SSA at Melpitz, Germany, by a factor of ?~??20. As a result, the nitrate partitioning fraction (ratio between particulate nitrate and the summation of particulate nitrate and gas-phase nitric acid) increased by about 20?% for the coarse-mode nitrate due to the overestimation of SSA at Melpitz. However, no significant difference in the partitioning fraction for the fine-mode nitrate was found. About 140?% overestimation of the coarse-mode nitrate resulted from the influence of SSA at Melpitz. In contrast, the overestimation of SSA inhibited the nitrate particle formation in the fine mode by about 20?% because of the increased consumption of precursor by coarse-mode nitrate formation.Quelle: http://www.atmos-chem-phys.net