5 results
Search Results
Now showing 1 - 5 of 5
- ItemAirborne observations of newly formed boundary layer aerosol particles under cloudy conditions(Katlenburg-Lindau : EGU, 2018) Altstädter, Barbara; Platis, Andreas; Jähn, Michael; Baars, Holger; Lückerath, Janine; Held, Andreas; Lampert, Astrid; Bange, Jens; Hermann, Markus; Wehner, BirgitThis study describes the appearance of ultrafine boundary layer aerosol particles under classical “non-favourable” conditions at the research site of TROPOS (Leibniz Institute for Tropospheric Research). Airborne measurements of meteorological and aerosol properties of the atmospheric boundary layer (ABL) were repeatedly performed with the unmanned aerial system ALADINA (Application of Light-weight Aircraft for Detecting IN-situ Aerosol) during three seasons between October 2013 and July 2015. More than 100 measurement flights were conducted on 23 different days with a total flight duration of 53 h. In 26 % of the cases, maxima of ultrafine particles were observed close to the inversion layer at altitudes between 400 and 600 m and the particles were rapidly mixed vertically and mainly transported downwards during short time intervals of cloud gaps. This study focuses on two measurement days affected by low-level stratocumulus clouds, but different wind directions (NE, SW) and minimal concentrations (< 4.6 µg m−3) of SO2, as a common indicator for precursor gases at ground. Taken from vertical profiles, the onset of clouds led to a non-linearity of humidity that resulted in an increased turbulence at the local-scale and caused fast nucleation (e.g. Bigg, 1997; Wehner et al., 2010), but in relation to rapid dilution of surrounding air, seen in sporadic clusters of ground data, so that ultrafine particles disappeared in the verticality. The typical “banana shape” (Heintzenberg et al., 2007) of new particle formation (NPF) and growth was not seen at ground and thus these days might not have been classified as NPF event days by pure surface studies.
- ItemHelicopter-borne observations of the continental background aerosol in combination with remote sensing and ground-based measurements(Katlenburg-Lindau : EGU, 2018) Düsing, Sebastian; Wehner, Birgit; Seifert, Patric; Ansmann, Albert; Baars, Holger; Ditas, Florian; Henning, Silvia; Ma, Nan; Poulain, Laurent; Siebert, Holger; Wiedensohler, Alfred; Macke, AndreasThis paper examines the representativeness of ground-based in situ measurements for the planetary boundary layer (PBL) and conducts a closure study between airborne in situ and ground-based lidar measurements up to an altitude of 2300 m. The related measurements were carried out in a field campaign within the framework of the High-Definition Clouds and Precipitation for Advancing Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE) in September 2013 in a rural background area of central Europe. The helicopter-borne probe ACTOS (Airborne Cloud and Turbulence Observation System) provided measurements of the aerosol particle number size distribution (PNSD), the aerosol particle number concentration (PNC), the number concentration of cloud condensation nuclei (CCN-NC), and meteorological atmospheric parameters (e.g., temperature and relative humidity). These measurements were supported by the ground-based 3+2 wavelength polarization lidar system PollyXT, which provided profiles of the particle backscatter coefficient (σbsc) for three wavelengths (355, 532, and 1064 nm). Particle extinction coefficient (σext) profiles were obtained by using a fixed backscatter-to-extinction ratio (also lidar ratio, LR). A new approach was used to determine profiles of CCN-NC for continental aerosol. The results of this new approach were consistent with the airborne in situ measurements within the uncertainties. In terms of representativeness, the PNSD measurements on the ground showed a good agreement with the measurements provided with ACTOS for lower altitudes. The ground-based measurements of PNC and CCN-NC are representative of the PBL when the PBL is well mixed. Locally isolated new particle formation events on the ground or at the top of the PBL led to vertical variability in the cases presented here and ground-based measurements are not entirely representative of the PBL. Based on Mie theory (Mie, 1908), optical aerosol properties under ambient conditions for different altitudes were determined using the airborne in situ measurements and were compared with the lidar measurements. The investigation of the optical properties shows that on average the airborne-based particle light backscatter coefficient is 50.1 % smaller for 1064 nm, 27.4 % smaller for 532 nm, and 29.5 % smaller for 355 nm than the measurements of the lidar system. These results are quite promising, since in situ measurement-based Mie calculations of the particle light backscattering are scarce and the modeling is quite challenging. In contrast, for the particle light extinction coefficient we found a good agreement. The airborne-based particle light extinction coefficient was just 8.2 % larger for 532 nm and 3 % smaller for 355 nm, for an assumed LR of 55 sr. The particle light extinction coefficient for 1064 nm was derived with a LR of 30 sr. For this wavelength, the airborne-based particle light extinction coefficient is 5.2 % smaller than the lidar measurements. For the first time, the lidar ratio of 30 sr for 1064 nm was determined on the basis of in situ measurements and the LR of 55 sr for 355 and 532 nm wavelength was reproduced for European continental aerosol on the basis of this comparison. Lidar observations and the in situ based aerosol optical properties agree within the uncertainties. However, our observations indicate that a determination of the PNSD for a large size range is important for a reliable modeling of aerosol particle backscattering.
- ItemThe HD(CP)2 Observational Prototype Experiment (HOPE) - An overview(Katlenburg-Lindau : EGU, 2017) Macke, Andreas; Seifert, Patric; Baars, Holger; Barthlott, Christian; Beekmans, Christoph; Behrendt, Andreas; Bohn, Birger; Brueck, Matthias; Bühl, Johannes; Crewell, Susanne; Damian, Thomas; Deneke, Hartwig; Düsing, Sebastian; Foth, Andreas; Di Girolamo, Paolo; Hammann, Eva; Heinze, Rieke; Hirsikko, Anne; Kalisch, John; Kalthoff, Norbert; Kinne, Stefan; Kohler, Martin; Löhnert, Ulrich; Madhavan, Bomidi Lakshmi; Maurer, Vera; Muppa, Shravan Kumar; Schween, Jan; Serikov, Ilya; Siebert, Holger; Simmer, Clemens; Späth, Florian; Steinke, Sandra; Träumner, Katja; Trömel, Silke; Wehner, Birgit; Wieser, Andreas; Wulfmeyer, Volker; Xie, XinxinThe HD(CP)2 Observational Prototype Experiment (HOPE) was performed as a major 2-month field experiment in Jülich, Germany, in April and May 2013, followed by a smaller campaign in Melpitz, Germany, in September 2013. HOPE has been designed to provide an observational dataset for a critical evaluation of the new German community atmospheric icosahedral non-hydrostatic (ICON) model at the scale of the model simulations and further to provide information on land-surface-atmospheric boundary layer exchange, cloud and precipitation processes, as well as sub-grid variability and microphysical properties that are subject to parameterizations. HOPE focuses on the onset of clouds and precipitation in the convective atmospheric boundary layer. This paper summarizes the instrument set-ups, the intensive observation periods, and example results from both campaigns.
HOPE-Jülich instrumentation included a radio sounding station, 4 Doppler lidars, 4 Raman lidars (3 of them provide temperature, 3 of them water vapour, and all of them particle backscatter data), 1 water vapour differential absorption lidar, 3 cloud radars, 5 microwave radiometers, 3 rain radars, 6 sky imagers, 99 pyranometers, and 5 sun photometers operated at different sites, some of them in synergy. The HOPE-Melpitz campaign combined ground-based remote sensing of aerosols and clouds with helicopter- and balloon-based in situ observations in the atmospheric column and at the surface.
HOPE provided an unprecedented collection of atmospheric dynamical, thermodynamical, and micro- and macrophysical properties of aerosols, clouds, and precipitation with high spatial and temporal resolution within a cube of approximately 10 × 10 × 10km3. HOPE data will significantly contribute to our understanding of boundary layer dynamics and the formation of clouds and precipitation. The datasets have been made available through a dedicated data portal.
First applications of HOPE data for model evaluation have shown a general agreement between observed and modelled boundary layer height, turbulence characteristics, and cloud coverage, but they also point to significant differences that deserve further investigations from both the observational and the modelling perspective. - ItemVertical aerosol particle exchange in the marine boundary layer estimated from helicopter-borne measurements in the Azores region(Katlenburg-Lindau : EGU, 2022) Lückerath, Janine; Held, Andreas; Siebert, Holger; Michalkow, Michel; Wehner, BirgitAerosol particles are important for radiation effects, cloud formation, and therefore the climate system. A detailed understanding of the spatial distribution of aerosol particles within the atmospheric boundary layer, which depends on sources and sinks, as well as long-range transport and vertical exchange, is important. Especially in marine regions, where the climate effect of clouds is comparably high, long-range transport with subsequent vertical mixing dominates over local aerosol sources. In this study, three different methods were applied to estimate the vertical aerosol particle flux in the marine boundary layer (MBL) and the vertical exchange between the MBL and the free troposphere (FT): eddy covariance (EC), flux–gradient similarity (K theory), and the mixed-layer gradient method (MLG). For the first time, MBL aerosol fluxes derived from these three methods were compared in the framework of the “Azores Stratocumulus Measurements of Radiation, Turbulence and Aerosols” (ACORES) field campaign in the Azores region in the northeastern Atlantic Ocean in July 2017. Meteorological parameters and aerosol and cloud properties were measured in the marine troposphere using the helicopter-borne measurement platform ACTOS (Airborne Cloud Turbulence Observation System). All three methods were applied to estimate the net particle exchange between MBL and FT. In many cases, the entrainment fluxes of the MLG method agreed within the range of uncertainty with the EC and K-theory flux estimates close to the top of the MBL, while the surface flux estimates of the different methods diverged. It was not possible to measure directly above the surface with the helicopter-borne payload, which might be a source of uncertainty in the surface fluxes. The observed particle fluxes at the top of the MBL ranged from 0 to 10×106 m−2 s−1 both in the upward and the downward direction, and the associated uncertainties were on the same order of magnitude. Even though the uncertainties of all three methods are considerable, the results of this study contribute to an improved understanding of the transport of particles between the MBL and FT and their distribution in the MBL.
- ItemOverview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept and initial results(Katlenburg-Lindau : EGU, 2020) Petäjä, Tuukka; Duplissy, Ella-Maria; Tabakova, Ksenia; Schmale, Julia; Altstädter, Barbara; Ancellet, Gerard; Arshinov, Mikhail; Balin, Yurii; Baltensperger, Urs; Bange, Jens; Beamish, Alison; Belan, Boris; Berchet, Antoine; Bossi, Rossana; Cairns, Warren R.L.; Ebinghaus, Ralf; El Haddad, Imad; Ferreira-Araujo, Beatriz; Franck, Anna; Huang, Lin; Hyvärinen, Antti; Humbert, Angelika; Kalogridis, Athina-Cerise; Konstantinov, Pavel; Lampert, Astrid; MacLeod, Matthew; Magand, Olivier; Mahura, Alexander; Marelle, Louis; Masloboev, Vladimir; Moisseev, Dmitri; Moschos, Vaios; Neckel, Niklas; Onishi, Tatsuo; Osterwalder, Stefan; Ovaska, Aino; Paasonen, Pauli; Panchenko, Mikhail; Pankratov, Fidel; Pernov, Jakob B.; Platis, Andreas; Popovicheva, Olga; Raut, Jean-Christophe; Riandet, Aurélie; Sachs, Torsten; Salvatori, Rosamaria; Salzano, Roberto; Schröder, Ludwig; Schön, Martin; Shevchenko, Vladimir; Skov, Henrik; Sonke, Jeroen E.; Spolaor, Andrea; Stathopoulos, Vasileios K.; Strahlendorff, Mikko; Thomas, Jennie L.; Vitale, Vito; Vratolis, Sterios; Barbante, Carlo; Chabrillat, Sabine; Dommergue, Aurélien; Eleftheriadis, Konstantinos; Heilimo, Jyri; Law, Kathy S.; Massling, Andreas; Noe, Steffen M.; Paris, Jean-Daniel; Prévôt, André S.H.; Riipinen, Ilona; Wehner, Birgit; Xie, Zhiyong; Lappalainen, Hanna K.The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.