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- ItemCAMP: An instrumented platform for balloon-borne aerosol particle studies in the lower atmosphere(Katlenburg-Lindau : Copernicus, 2022) Pilz, Christian; Düsing, Sebastian; Wehner, Birgit; Müller, Thomas; Siebert, Holger; Voigtländer, Jens; Lonardi, MichaelAirborne observations of vertical aerosol particle distributions are crucial for detailed process studies and model improvements. Tethered balloon systems represent a less expensive alternative to aircraft to probe shallow atmospheric boundary layers (ABLs). This study presents the newly developed cubic aerosol measurement platform (CAMP) for balloon-borne observations of aerosol particle microphysical properties. With an edge length of 35 cm and a weight of 9 kg, the cube is an environmentally robust instrument platform intended for measurements at low temperatures, with a particular focus on applications in cloudy Arctic ABLs. The aerosol instrumentation on board CAMP comprises two condensation particle counters with different lower detection limits, one optical particle size spectrometer, and a miniaturized absorption photometer. Comprehensive calibrations and characterizations of the instruments were performed in laboratory experiments. The first field study with a tethered balloon system took place at the Leibniz Institute for Tropospheric Research (TROPOS) station in Melpitz, Germany, in the winter of 2019. At ambient temperatures between-8 and 15 C, the platform was operated up to a 1.5 km height on 14 flights under both clear-sky and cloudy conditions. The continuous aerosol observations at the ground station served as a reference for evaluating the CAMP measurements. Exemplary profiles are discussed to elucidate the performance of the system and possible process studies. Based on the laboratory instrument characterizations and the observations during the field campaign, CAMP demonstrated the capability to provide comprehensive aerosol particle measurements in cold and cloudy ABLs.
- ItemAerosol activation characteristics and prediction at the central European ACTRIS research station of Melpitz, Germany(Katlenburg-Lindau : EGU, 2022) Wang, Yuan; Henning, Silvia; Poulain, Laurent; Lu, Chunsong; Stratmann, Frank; Wang, Yuying; Niu, Shengjie; Pöhlker, Mira L.; Herrmann, Hartmut; Wiedensohler, AlfredUnderstanding aerosol particle activation is essential for evaluating aerosol indirect effects (AIEs) on climate. Long-term measurements of aerosol particle activation help to understand the AIEs and narrow down the uncertainties of AIEs simulation. However, they are still scarce. In this study, more than 4 years of comprehensive aerosol measurements were utilized at the central European research station of Melpitz, Germany, to gain insight into the aerosol particle activation and provide recommendations on improving the prediction of number concentration of cloud condensation nuclei (CCN, NCCN). (1) The overall CCN activation characteristics at Melpitz are provided. As supersaturation (SS) increases from 0.1% to 0.7%, the median NCCN increases from 399 to 2144cm-3, which represents 10% to 48% of the total particle number concentration with a diameter range of 10-800nm, while the median hygroscopicity factor (κ) and critical diameter (Dc) decrease from 0.27 to 0.19 and from 176 to 54nm, respectively. (2) Aerosol particle activation is highly variable across seasons, especially at low-SS conditions. At SSCombining double low line0.1%, the median NCCN and activation ratio (AR) in winter are 1.6 and 2.3 times higher than the summer values, respectively. (3) Both κ and the mixing state are size-dependent. As the particle diameter (Dp) increases, κ increases at Dp of 1/440 to 100nm and almost stays constant at Dp of 100 to 200nm, whereas the degree of the external mixture keeps decreasing at Dp of 1/440 to 200nm. The relationships of κ vs. Dp and degree of mixing vs. Dp were both fitted well by a power-law function. (4) Size-resolved κ improves the NCCN prediction. We recommend applying the κ-Dp power-law fit for NCCN prediction at Melpitz, which performs better than using the constant κ of 0.3 and the κ derived from particle chemical compositions and much better than using the NCCN (AR) vs. SS relationships. The κ-Dp power-law fit measured at Melpitz could be applied to predict NCCN for other rural regions. For the purpose of improving the prediction of NCCN, long-term monodisperse CCN measurements are still needed to obtain the κ-Dp relationships for different regions and their seasonal variations.
- ItemRole of the dew water on the ground surface in HONO distribution: A case measurement in Melpitz(Katlenburg-Lindau : EGU, 2020) Ren, Yangang; Stieger, Bastian; Spindler, Gerald; Grosselin, Benoit; Mellouki, Abdelwahid; Tuch, Thomas; Wiedensohler, Alfred; Herrmann, HartmutTo characterize the role of dew water for the ground surface HONO distribution, nitrous acid (HONO) measurements with a Monitor for AeRosols and Gases in ambient Air (MARGA) and a LOng Path Absorption Photometer (LOPAP) instrument were performed at the Leibniz Institute for Tropospheric Research (TROPOS) research site in Melpitz, Germany, from 19 to 29 April 2018. The dew water was also collected and analyzed from 8 to 14 May 2019 using a glass sampler. The high time resolution of HONO measurements showed characteristic diurnal variations that revealed that (i) vehicle emissions are a minor source of HONO at Melpitz station; (ii) the heterogeneous conversion of NO2 to HONO on the ground surface dominates HONO production at night; (iii) there is significant nighttime loss of HONO with a sink strength of 0.16±0.12ppbv h-1; and (iv) dew water with mean NO-2 of 7.91±2.14 μgm-2 could serve as a temporary HONO source in the morning when the dew droplets evaporate. The nocturnal observations of HONO and NO2 allowed the direct evaluation of the ground uptake coefficients for these species at night: γNO2→HONO = 2.4±10-7 to 3.5±10-6, γHONO;ground = 1.7×10-5 to 2.8×10-4. A chemical model demonstrated that HONO deposition to the ground surface at night was 90 %-100% of the calculated unknown HONO source in the morning. These results suggest that dew water on the ground surface was controlling the temporal HONO distribution rather than straightforward NO2-HONO conversion. This can strongly enhance the OH reactivity throughout the morning time or in other planted areas that provide a large amount of ground surface based on the OH production rate calculation. © 2020 Copernicus GmbH. All rights reserved.
- ItemMulti-year ACSM measurements at the central European research station Melpitz (Germany)-Part 1: Instrument robustness, quality assurance, and impact of upper size cutoff diameter(Katlenburg-Lindau : Copernicus, 2020) Poulain, Laurent; Spindler, Gerald; Grüner, Achim; Tuch, Thomas; Stieger, Bastian; van Pinxteren, Dominik; Petit, Jean-Eudes; Favez, Olivier; Herrmann, Hartmut; Wiedensohler, AlfredThe aerosol chemical speciation monitor (ACSM) is nowadays widely used to identify and quantify the main components of fine particles in ambient air. As such, its deployment at observatory platforms is fully incorporated within the European Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS). Regular intercomparisons are organized at the Aerosol Chemical Monitoring Calibration Center (ACMCC; part of the European Center for Aerosol Calibration, Paris, France) to ensure the consistency of the dataset, as well as instrumental performance and variability. However, in situ quality assurance remains a fundamental aspect of the instrument's stability. Here, we present and discuss the main outputs of long-term quality assurance efforts achieved for ACSM measurements at the research station Melpitz (Germany) since 2012 onwards. In order to validate the ACSM measurements over the years and to characterize seasonal variations, nitrate, sulfate, ammonium, organic, and particle mass concentrations were systematically compared against the collocated measurements of daily offline high-volume PM1 and PM2:5 filter samples and particle number size distribution (PNSD) measurements. Mass closure analysis was made by comparing the total particle mass (PM) concentration obtained by adding the mass concentration of equivalent black carbon (eBC) from the multi-angle absorption photometer (MAAP) to the ACSM chemical composition, to that of PM1 and PM2:5 during filter weighing, as well as to the derived mass concentration of PNSD. A combination of PM1 and PM2:5 filter samples helped identifying the critical importance of the upper size cutoff of the ACSM during such exercises. The ACSM-MAAP-derived mass concentrations systematically deviated from the PM1 mass when the mass concentration of the latter represented less than 60% of PM2:5, which was linked to the transmission efficiency of the aerodynamic lenses of the ACSM. The best correlations are obtained for sulfate (slopeD 0:96; R2 D 0:77) and total PM (slopeD 1:02; R2 D 0:90). Although, sulfate did not exhibit a seasonal dependency, total PM mass concentration revealed a small seasonal variability linked to the increase in non-water-soluble fractions. The nitrate suffers from a loss of ammonium nitrate during filter collection, and the contribution of organo-nitrate compounds to the ACSM nitrate signal make it difficult to directly compare the two methods. The contribution of m=z 44 (f44) to the total organic mass concentration was used to convert the ACSM organic mass (OM) to organic carbon (OC) by using a similar approach as for the aerosol mass spectrometer (AMS). The resulting estimated OCACSM was compared with the measured OCPM1 (slopeD 0:74; R2 D 0:77), indicating that the f44 signal was relatively free of interferences during this period. The PM2:5 filter samples use for the ACSM data quality might suffer from a systematic bias due to a size truncation effect as well as to the presence of chemical species that cannot be detected by the ACSM in coarse mode (e.g., sodium nitrate and sodium sulfate). This may lead to a systematic underestimation of the ACSM particle mass concentration and/or a positive artifact that artificially decreases the discrepancies between the two methods. Consequently, ACSM data validation using PM2:5 filters has to be interpreted with extreme care. The particle mass closure with the PNSD was satisfying (slopeD 0:77; R2 D 0:90 over the entire period), with a slight overestimation of the mobility particle size spectrometer (MPSS)-derived mass concentration in winter. This seasonal variability was related to a change on the PNSD and a larger contribution of the supermicrometer particles in winter. This long-term analysis between the ACSM and other collocated instruments confirms the robustness of the ACSM and its suitability for long-term measurements. Particle mass closure with the PNSD is strongly recommended to ensure the stability of the ACSM. A near-real-time mass closure procedure within the entire ACTRIS-ACSM network certainly represents an optimal quality control and assurance of both warranting the quality assurance of the ACSM measurements as well as identifying cross-instrumental biases. © Author(s) 2020.
- ItemVariability in the mass absorption cross section of black carbon (BC) aerosols is driven by BC internal mixing state at a central European background site (Melpitz, Germany) in winter(Katlenburg-Lindau : European Geosciences Union, 2021) Yuan, Jinfeng; Modini, Robin Lewis; Zanatta, Marco; Herber, Andreas B.; Müller, Thomas; Wehner, Birgit; Poulain, Laurent; Tuch, Thomas; Baltensperger, Urs; Gysel-Beer, MartinProperties of atmospheric black carbon (BC) particles were characterized during a field experiment at a rural background site (Melpitz, Germany) in February 2017. BC absorption at a wavelength of 870 nm was measured by a photoacoustic extinctiometer, and BC physical properties (BC mass concentration, core size distribution and coating thickness) were measured by a single-particle soot photometer (SP2). Additionally, a catalytic stripper was used to intermittently remove BC coatings by alternating between ambient and thermo-denuded conditions. From these data the mass absorption cross section of BC (MACBC) and its enhancement factor (EMAC) were inferred for essentially waterfree aerosol as present after drying to low relative humidity (RH). Two methods were applied independently to investigate the coating effect on EMAC: A correlation method (MACBC; ambient vs. BC coating thickness) and a denuding method (MACBC; ambient vs. MACBC; denuded). Observed EMAC values varied from 1.0 to 1.6 (lower limit from denuding method) or 1:2 to 1.9 (higher limit from correlation method), with the mean coating volume fraction ranging from 54% to 78% in the dominating mass equivalent BC core diameter range of 200?220 nm.MACBC and EMAC were strongly correlated with coating thickness of BC. By contrast, other potential drivers of EMAC variability, such as different BC sources (air mass origin and absorption Angström exponent), coating composition (ratio of inorganics to organics) and BC core size distribution, had only minor effects. These results for ambient BC measured at Melpitz during winter show that the lensing effect caused by coatings on BC is the main driver of the variations in MACBC and EMAC, while changes in other BC particle properties such as source, BC core size or coating composition play only minor roles at this rural background site with a large fraction of aged particles. Indirect evidence suggests that potential dampening of the lensing effect due to unfavorable morphology was most likely small or even negligible.