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- ItemMineral dust in Central Asia: Combining lidar and other measurements during the Central Asian dust experiment (CADEX)(Les Ulis : EDP Sciences, 2018) Althausen, Dietrich; Hofer, Julian; Abdullaev, Sabur; Makhmudov, Abduvosit; Baars, Holger; Engelmann, Ronny; Wadinga Fomba, Khanneh; Müller, Konrad; Schettler, Georg; Klüser, Lars; Kandler, Konrad; Nicolae, D.; Makoto, A.; Vassilis, A.; Balis, D.; Behrendt, A.; Comeron, A.; Gibert, F.; Landulfo, E.; McCormick, M.P.; Senff, C.; Veselovskii, I.; Wandinger, U.Mineral dust needs to be characterized comprehensively since it contributes to the climate change in Tajikistan / Central Asia. Lidar results from the measurements of mineral dust during CADEX are compared with results of sun photometer measurements, satellite-based measurements, and chemical analysis of ground samples. Although the dust is often advected from far-range sources, it impacts on the local conditions considerably.
- ItemAerosol Particle and Black Carbon Emission Factors of Vehicular Fleet in Manila, Philippines(Basel, Switzerland : MDPI AG, 2019) Madueño, Leizel; Kecorius, Simonas; Birmili, Wolfram; Müller, Thomas; Simpas, James; Vallar, Edgar; Galvez, Maria Cecilia; Cayetano, Mylene; Wiedensohler, AlfredPoor air quality has been identified as one of the main risks to human health, especially in developing regions, where the information on physical chemical properties of air pollutants is lacking. To bridge this gap, we conducted an intensive measurement campaign in Manila, Philippines to determine the emission factors (EFs) of particle number (PN) and equivalent black carbon (BC). The focus was on public utility jeepneys (PUJ), equipped with old technology diesel engines, widely used for public transportation. The EFs were determined by aerosol physical measurements, fleet information, and modeled dilution using the Operational Street Pollution Model (OSPM). The results show that average vehicle EFs of PN and BC in Manila is up to two orders of magnitude higher than European emission standards. Furthermore, a PUJ emits up to seven times more than a light-duty vehicles (LDVs) and contribute to more than 60% of BC emission in Manila. Unfortunately, traffic restrictions for heavy-duty vehicles do not apply to PUJs. The results presented in this work provide a framework to help support targeted traffic interventions to improve urban air quality not only in Manila, but also in other countries with a similar fleet composed of old-technology vehicles. © 2019 by the authors.
- ItemResults and recommendations from an intercomparison of six Hygroscopicity-TDMA systems(München : European Geopyhsical Union, 2011) Massling, A.; Niedermeier, N.; Hennig, T.; Fors, E.O.; Swietlicki, E.; Ehn, M.; Hämeri, K.; Villani, P.; Laj, P.; Good, N.; McFiggans, G.; Wiedensohler, A.The performance of six custom-built Hygrocopicity-Tandem Differential Mobility Analyser (H-TDMA) systems was investigated in the frame of an international calibration and intercomparison workshop held in Leipzig, February 2006. The goal of the workshop was to harmonise H-TDMA measurements and develop recommendations for atmospheric measurements and their data evaluation. The H-TDMA systems were compared in terms of the sizing of dry particles, relative humidity (RH) uncertainty, and consistency in determination of number fractions of different hygroscopic particle groups. The experiments were performed in an air-conditioned laboratory using ammonium sulphate particles or an external mixture of ammonium sulphate and soot particles. The sizing of dry particles of the six H-TDMA systems was within 0.2 to 4.2% of the selected particle diameter depending on investigated size and individual system. Measurements of ammonium sulphate aerosol found deviations equivalent to 4.5% RH from the set point of 90% RH compared to results from previous experiments in the literature. Evaluation of the number fraction of particles within the clearly separated growth factor modes of a laboratory generated externally mixed aerosol was done. The data from the H-TDMAs was analysed with a single fitting routine to investigate differences caused by the different data evaluation procedures used for each H-TDMA. The differences between the H-TDMAs were reduced from +12/−13% to +8/−6% when the same analysis routine was applied. We conclude that a common data evaluation procedure to determine number fractions of externally mixed aerosols will improve the comparability of H-TDMA measurements. It is recommended to ensure proper calibration of all flow, temperature and RH sensors in the systems. It is most important to thermally insulate the aerosol humidification unit and the second DMA and to monitor these temperatures to an accuracy of 0.2 °C. For the correct determination of external mixtures, it is necessary to take into account size-dependent losses due to diffusion in the plumbing between the DMAs and in the aerosol humidification unit.
- ItemCloud radar with hybrid mode towards estimation of shape and orientation of ice crystals(München : European Geopyhsical Union, 2016) Myagkov, A.; Seifert, P.; Bauer-Pfundstein, M.; Wandinger, U.This paper is devoted to the experimental quantitative characterization of the shape and orientation distribution of ice particles in clouds. The characterization is based on measured and modeled elevation dependencies of the polarimetric parameters differential reflectivity and correlation coefficient. The polarimetric data are obtained using a newly developed 35 GHz cloud radar MIRA-35 with hybrid polarimetric configuration and scanning capabilities. The full procedure chain of the technical implementation and the realization of the setup of the hybrid-mode cloud radar for the shape determination are presented. This includes the description of phase adjustments in the transmitting paths, the introduction of the general data processing scheme, correction of the data for the differences of amplifications and electrical path lengths in the transmitting and receiving channels, the rotation of the polarization basis by 45°, the correction of antenna effects on polarimetric measurements, the determination of spectral polarimetric variables, and the formulation of a scheme to increase the signal-to-noise ratio. Modeling of the polarimetric variables is based on existing back-scattering models assuming the spheroidal representation of cloud scatterers. The parameters retrieved from the model are polarizability ratio and degree of orientation, which can be assigned to certain particle orientations and shapes. The developed algorithm is applied to a measurement of the hybrid-mode cloud radar taken on 20 October 2014 in Cabauw, the Netherlands, in the framework of the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) campaign. The case study shows the retrieved polarizability ratio and degree of orientation of ice particles for a cloud system of three cloud layers at different heights. Retrieved polarizability ratios are 0.43, 0.85, and 1.5 which correspond to oblate, quasi-spherical, and columnar ice particles, respectively. It is shown that the polarizability ratio is useful for the detection of aggregation/riming processes. The orientation of oblate and prolate particles is estimated to be close to horizontal while quasi-spherical particles were found to be more randomly oriented.
- ItemDesign and performance of a three-wavelength LED-based total scatter and backscatter integrating nephelometer(München : European Geopyhsical Union, 2011) Müller, T.; Laborde, M.; Kassell, G.; Wiedensohler, A.Integrating nephelometers are instruments that directly measure a value close to the light scattering coefficient of airborne particles. Different models of nephelometers have been used for decades for monitoring and research applications. Now, a series of nephelometers (Ecotech models M9003, Aurora 1000 and Aurora 3000) with newly designed light sources based on light emitting diodes are available. This article reports on the design of these integrating nephelometers and a comparison of the Aurora 3000 to another commercial instrument (TSI model 3563) that uses an incandescent lamp. Both instruments are three-wavelength, total and backscatter integrating nephelometers. We present a characterization of the new light source design of the Aurora 3000 and provide parameterizations for its angular sensitivity functions. These parameterizations facilitate to correct for measurement artefacts using Mie-theory. Furthermore, correction factors are provided as a function of the Ångström exponent. Comparison measurements against the TSI 3563 with laboratory generated white particles and ambient air are also shown and discussed. Both instruments agree well within the calibration uncertainties and detection limit for total scattering with differences less than 5 %. Differences for backscattering are higher by up to 11 %. Highest differences were found for the longest wavelengths, where the signal to noise ratio is lowest. Differences at the blue and green wavelengths are less than 4 % and 3 %, respectively, for both total and backscattering.
- ItemNear-surface profiles of aerosol number concentration and temperature over the Arctic Ocean(München : European Geopyhsical Union, 2011) Held, A.; Orsini, D.A.; Vaattovaara, P.; Tjernström, M.; Leck, C.Temperature and particle number concentration profiles were measured at small height intervals above open and frozen leads and snow surfaces in the central Arctic. The device used was a gradient pole designed to investigate potential particle sources over the central Arctic Ocean. The collected data were fitted according to basic logarithmic flux-profile relationships to calculate the sensible heat flux and particle deposition velocity. Independent measurements by the eddy covariance technique were conducted at the same location. General agreement was observed between the two methods when logarithmic profiles could be fitted to the gradient pole data. In general, snow surfaces behaved as weak particle sinks with a maximum deposition velocity vd = 1.3 mm s−1 measured with the gradient pole. The lead surface behaved as a weak particle source before freeze-up with an upward flux Fc = 5.7 × 104 particles m−2 s−1, and as a relatively strong heat source after freeze-up, with an upward maximum sensible heat flux H = 13.1 W m−2. Over the frozen lead, however, we were unable to resolve any significant aerosol profiles.
- ItemDust mass, cloud condensation nuclei, and ice-nucleating particle profiling with polarization lidar: Updated POLIPHON conversion factors from global AERONET analysis(Göttingen : Copernicus GmbH, 2019) Ansmann, A.; Mamouri, R.-E.; Hofer, J.; Baars, H.; Althausen, D.; Abdullaev, S.F.The POLIPHON (Polarization Lidar Photometer Networking) method permits the retrieval of particle number, surface area, and volume concentration for dust and non-dust aerosol components. The obtained microphysical properties are used to estimate height profiles of particle mass, cloud condensation nucleus (CCN) and ice-nucleating particle (INP) concentrations. The conversion of aerosol-type-dependent particle extinction coefficients, derived from polarization lidar observations, into the aerosol microphysical properties (number, surface area, volume) forms the central part of the POLIPHON computations. The conversion parameters are determined from Aerosol Robotic Network (AERONET) aerosol climatologies of optical and microphysical properties. In this article, we focus on the dust-related POLIPHON retrieval products and present an extended set of dust conversion factors considering all relevant deserts around the globe. We apply the new conversion factor set to a dust measurement with polarization lidar in Dushanbe, Tajikistan, in central Asia. Strong aerosol layering was observed with mineral dust advected from Kazakhstan (0-2km height), Iran (2-5km), the Arabian peninsula (5-7km), and the Sahara (8-10km). POLIPHON results obtained with different sets of conversion parameters were contrasted in this central Asian case study and permitted an estimation of the conversion uncertainties.
- ItemThe automated multiwavelength Raman polarization and water-vapor lidar PollyXT: The neXT generation(München : European Geopyhsical Union, 2016) Engelmann, Ronny; Kanitz, Thomas; Baars, Holger; Heese, Birgit; Althausen, Dietrich; Skupin, Annett; Wandinger, Ulla; Komppula, Mika; Stachlewska, Iwona S.; Amiridis, Vassilis; Marinou, Eleni; Mattis, Ina; Linné, Holger; Ansmann, AlbertThe atmospheric science community demands autonomous and quality-assured vertically resolved measurements of aerosol and cloud properties. For this purpose, a portable lidar called Polly was developed at TROPOS in 2003. The lidar system was continuously improved with gained experience from the EARLINET community, involvement in worldwide field campaigns, and international institute collaborations within the last 10 years. Here we present recent changes of the setup of the portable multiwavelength Raman and polarization lidar PollyXT and discuss the improved capabilities of the system by means of a case study. The latest system developments include an additional near-range receiver unit for Raman measurements of the backscatter and extinction coefficient down to 120 m above ground, a water-vapor channel, and channels for simultaneous measurements of the particle linear depolarization ratio at 355 and 532 nm. Quality improvements were achieved by systematically following the EARLINET guidelines and the international PollyNET quality assurance developments. A modified ship radar ensures measurements in agreement with air-traffic safety regulations and allows for 24∕7 monitoring of the atmospheric state with PollyXT.
- ItemEARLINET Single Calculus Chain – overview on methodology and strategy(München : European Geopyhsical Union, 2015) D'Amico, Giuseppe; Amodeo, A.; Baars, H.; Binietoglou, I.; Freudenthaler, V.; Mattis, I.; Wandinger, U.; Pappalardo, G.In this paper we describe the EARLINET Single Calculus Chain (SCC), a tool for the automatic analysis of lidar measurements. The development of this tool started in the framework of EARLINET-ASOS (European Aerosol Research Lidar Network – Advanced Sustainable Observation System); it was extended within ACTRIS (Aerosol, Clouds and Trace gases Research InfraStructure Network), and it is continuing within ACTRIS-2. The main idea was to develop a data processing chain that allows all EARLINET stations to retrieve, in a fully automatic way, the aerosol backscatter and extinction profiles starting from the raw lidar data of the lidar systems they operate. The calculus subsystem of the SCC is composed of two modules: a pre-processor module which handles the raw lidar data and corrects them for instrumental effects and an optical processing module for the retrieval of aerosol optical products from the pre-processed data. All input parameters needed to perform the lidar analysis are stored in a database to keep track of all changes which may occur for any EARLINET lidar system over the time. The two calculus modules are coordinated and synchronized by an additional module (daemon) which makes the whole analysis process fully automatic. The end user can interact with the SCC via a user-friendly web interface. All SCC modules are developed using open-source and freely available software packages. The final products retrieved by the SCC fulfill all requirements of the EARLINET quality assurance programs on both instrumental and algorithm levels. Moreover, the manpower needed to provide aerosol optical products is greatly reduced and thus the near-real-time availability of lidar data is improved. The high-quality of the SCC products is proven by the good agreement between the SCC analysis, and the corresponding independent manual retrievals. Finally, the ability of the SCC to provide high-quality aerosol optical products is demonstrated for an EARLINET intense observation period.
- ItemRadiative budget and cloud radiative effect over the Atlantic from ship-based observations(München : European Geopyhsical Union, 2012) Kalisch, J.; Macke, A.The aim of this study is to determine cloud-type resolved cloud radiative budgets and cloud radiative effects from surface measurements of broadband radiative fluxes over the Atlantic Ocean. Furthermore, based on simultaneous observations of the state of the cloudy atmosphere, a radiative closure study has been performed by means of the ECHAM5 single column model in order to identify the model's ability to realistically reproduce the effects of clouds on the climate system. An extensive database of radiative and atmospheric measurements has been established along five meridional cruises of the German research icebreaker Polarstern. Besides pyranometer and pyrgeometer for downward broadband solar and thermal radiative fluxes, a sky imager and a microwave radiometer have been utilized to determine cloud fraction and cloud type on the one hand and temperature and humidity profiles as well as liquid water path for warm non-precipitating clouds on the other hand. Averaged over all cruise tracks, we obtain a total net (solar + thermal) radiative flux of 144 W m−2 that is dominated by the solar component. In general, the solar contribution is large for cirrus clouds and small for stratus clouds. No significant meridional dependencies were found for the surface radiation budgets and cloud effects. The strongest surface longwave cloud effects were shown in the presence of low level clouds. Clouds with a high optical density induce strong negative solar radiative effects under high solar altitudes. The mean surface net cloud radiative effect is −33 W m−2. For the purpose of quickly estimating the mean surface longwave, shortwave and net cloud effects in moderate, subtropical and tropical climate regimes, a new parameterisation was created, considering the total cloud amount and the solar zenith angle. The ECHAM5 single column model provides a surface net cloud effect that is more cooling by 17 W m−2 compared to the radiation observations. This overestimation in solar cooling is mostly caused by the shortwave impact of convective clouds. The latter show a large overestimation in solar cooling of up to 114 W m−2. Mean cloud radiative effects of cirrus and stratus clouds were simulated close to the observations.