Auflistung nach Autor:in "Wolke, Ralf"

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A parameterization of the heterogeneous hydrolysis of N2O5 for mass-based aerosol models
(2018) Chen, Ying-Yuan; Birmili, Wolfram; Wolke, Ralf; Ran, Liang
The heterogeneous hydrolysis of N2O5 on the surface of deliquescent aerosol leads to HNO3 formation and acts as a major sink of NOx in the atmosphere during night-time. The reaction constant of this heterogeneous hydrolysis is determined by temperature (T), relative humidity (RH), aerosol particle composition, and the surface area concentration (S). However, these parameters were not comprehensively considered in the parameterization of the heterogeneous hydrolysis of N2O5 in previous mass-based 3-D aerosol modelling studies. In this investigation, we propose a sophisticated parameterization (NewN2O5) of N2O5 heterogeneous hydrolysis with respect to T, RH, aerosol particle compositions, and S based on laboratory experiments. We evaluated closure between NewN2O5 and a state-of-the-art parameterization based on a sectional aerosol treatment. The comparison showed a good linear relationship (R?=??0.91) between these two parameterizations. NewN2O5 was incorporated into a 3-D fully online coupled model, COSMOŃMUSCAT, with the mass-based aerosol treatment. As a case study, we used the data from the HOPE Melpitz campaign (10Ń25 September 2013) to validate model performance. Here, we investigated the improvement of nitrate prediction over western and central Europe. The modelled particulate nitrate mass concentrations ([NO3-]) were validated by filter measurements over Germany (Neuglobsow, Schmücke, Zingst, and Melpitz). The modelled [NO3-] was significantly overestimated for this period by a factor of 5Ń19, with the corrected NH3 emissions (reduced by 50?%) and the original parameterization of N2O5 heterogeneous hydrolysis. The NewN2O5 significantly reduces the overestimation of [NO3-] by ?~??35?%. Particularly, the overestimation factor was reduced to approximately 1.4 in our case study (12, 17Ń18 and 25 September 2013) when [NO3-] was dominated by local chemical formations. In our case, the suppression of organic coating was negligible over western and central Europe, with an influence on [NO3-] of less than 2?% on average and 20?% at the most significant moment. To obtain a significant impact of the organic coating effect, N2O5, SOA, and NH3 need to be present when RH is high and T is low. However, those conditions were rarely fulfilled simultaneously over western and central Europe. Hence, the organic coating effect on the reaction probability of N2O5 may not be as significant as expected over western and central Europe. Quelle: https://www.atmos-chem-phys.net/
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
KLENOS - Einfluss einer Änderung der Energiepolitik und des Klimas auf die Luftqualität sowie Konsequenzen für die Einhaltung von Immissionsgrenzwerten und Prüfung weitergehender emissionsmindernder Maßnahmen
(2016) Pavlik, Dirk; Heidenreich, Majana; Wolke, Ralf; Institut für Hydrologie und Meteorologie (Dresden); Deutschland. Umweltbundesamt; Kessinger, Susan
High concentrations of air pollutants, especially particulate Matter (PM10) and ground-level ozone, are known for their negative impacts on human health and in the case of ozone even on vegetation. As a member of the European Union, the Federal Republic of Germany is responsible for ensuring the compliance of immission limits according to the Directive on Ambient Air Quality and Clean Air for Europe (2008/50/EG) and the 39th Ordinance for Implementing the Federal Immission Control Act. To intervene at an early stage with emission-reducing measures an estimation of future air quality is required. Changes of meteorological parameters associated with climate change and political decisions that affect the emissions of conventional pollutants have a considerable impact on future air quality. Thus, both factors directly affect the compliance of applicable immission limit values in future. The importance of these factors on the development of air pollution, as well as their coupled impacts, can only be investigated with an analysis of appropriate climate change and emission scenarios. The aim of this research and development project KLENOS is to quantify the impacts of climate change and energy policy change on air quality with a scenario approach. It involves the implementation of regional climate and subsequent chemical transport simulations. A further objective is the identification of typical weather types, which are related to the exceedance of limit values for PM10 and ozone. Based on long climate simulations future frequency of these typical weather types and therefore future tendencies of the exceedance of limit values for PM10 and ozone can be estimated.
Quelle: Forschungsbericht
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